1//===- LowerTypeTests.cpp - type metadata lowering pass -------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass lowers type metadata and calls to the llvm.type.test intrinsic.
10// It also ensures that globals are properly laid out for the
11// llvm.icall.branch.funnel intrinsic.
12// See http://llvm.org/docs/TypeMetadata.html for more information.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Transforms/IPO/LowerTypeTests.h"
17#include "llvm/ADT/APInt.h"
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/ADT/EquivalenceClasses.h"
21#include "llvm/ADT/PointerUnion.h"
22#include "llvm/ADT/STLExtras.h"
23#include "llvm/ADT/SetVector.h"
24#include "llvm/ADT/SmallVector.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/ADT/StringRef.h"
27#include "llvm/ADT/TinyPtrVector.h"
28#include "llvm/Analysis/LoopInfo.h"
29#include "llvm/Analysis/PostDominators.h"
30#include "llvm/Analysis/TargetTransformInfo.h"
31#include "llvm/Analysis/TypeMetadataUtils.h"
32#include "llvm/Analysis/ValueTracking.h"
33#include "llvm/IR/Attributes.h"
34#include "llvm/IR/BasicBlock.h"
35#include "llvm/IR/Constant.h"
36#include "llvm/IR/Constants.h"
37#include "llvm/IR/DataLayout.h"
38#include "llvm/IR/DerivedTypes.h"
39#include "llvm/IR/Function.h"
40#include "llvm/IR/GlobalAlias.h"
41#include "llvm/IR/GlobalObject.h"
42#include "llvm/IR/GlobalValue.h"
43#include "llvm/IR/GlobalVariable.h"
44#include "llvm/IR/IRBuilder.h"
45#include "llvm/IR/InlineAsm.h"
46#include "llvm/IR/Instruction.h"
47#include "llvm/IR/Instructions.h"
48#include "llvm/IR/IntrinsicInst.h"
49#include "llvm/IR/Intrinsics.h"
50#include "llvm/IR/LLVMContext.h"
51#include "llvm/IR/MDBuilder.h"
52#include "llvm/IR/Metadata.h"
53#include "llvm/IR/Module.h"
54#include "llvm/IR/ModuleSummaryIndex.h"
55#include "llvm/IR/ModuleSummaryIndexYAML.h"
56#include "llvm/IR/Operator.h"
57#include "llvm/IR/PassManager.h"
58#include "llvm/IR/ProfDataUtils.h"
59#include "llvm/IR/ReplaceConstant.h"
60#include "llvm/IR/Type.h"
61#include "llvm/IR/Use.h"
62#include "llvm/IR/User.h"
63#include "llvm/IR/Value.h"
64#include "llvm/Support/Allocator.h"
65#include "llvm/Support/Casting.h"
66#include "llvm/Support/CommandLine.h"
67#include "llvm/Support/Debug.h"
68#include "llvm/Support/Error.h"
69#include "llvm/Support/ErrorHandling.h"
70#include "llvm/Support/FileSystem.h"
71#include "llvm/Support/MathExtras.h"
72#include "llvm/Support/MemoryBuffer.h"
73#include "llvm/Support/TrailingObjects.h"
74#include "llvm/Support/YAMLTraits.h"
75#include "llvm/Support/raw_ostream.h"
76#include "llvm/TargetParser/Triple.h"
77#include "llvm/Transforms/IPO.h"
78#include "llvm/Transforms/Utils/BasicBlockUtils.h"
79#include "llvm/Transforms/Utils/ModuleUtils.h"
80#include <algorithm>
81#include <cassert>
82#include <cstdint>
83#include <set>
84#include <string>
85#include <system_error>
86#include <utility>
87#include <vector>
88
89using namespace llvm;
90using namespace lowertypetests;
91
92#define DEBUG_TYPE "lowertypetests"
93
94STATISTIC(ByteArraySizeBits, "Byte array size in bits");
95STATISTIC(ByteArraySizeBytes, "Byte array size in bytes");
96STATISTIC(NumByteArraysCreated, "Number of byte arrays created");
97STATISTIC(NumTypeTestCallsLowered, "Number of type test calls lowered");
98STATISTIC(NumTypeIdDisjointSets, "Number of disjoint sets of type identifiers");
99
100static cl::opt<bool> AvoidReuse(
101 "lowertypetests-avoid-reuse",
102 cl::desc("Try to avoid reuse of byte array addresses using aliases"),
103 cl::Hidden, cl::init(Val: true));
104
105static cl::opt<PassSummaryAction> ClSummaryAction(
106 "lowertypetests-summary-action",
107 cl::desc("What to do with the summary when running this pass"),
108 cl::values(clEnumValN(PassSummaryAction::None, "none", "Do nothing"),
109 clEnumValN(PassSummaryAction::Import, "import",
110 "Import typeid resolutions from summary and globals"),
111 clEnumValN(PassSummaryAction::Export, "export",
112 "Export typeid resolutions to summary and globals")),
113 cl::Hidden);
114
115static cl::opt<std::string> ClReadSummary(
116 "lowertypetests-read-summary",
117 cl::desc("Read summary from given YAML file before running pass"),
118 cl::Hidden);
119
120static cl::opt<std::string> ClWriteSummary(
121 "lowertypetests-write-summary",
122 cl::desc("Write summary to given YAML file after running pass"),
123 cl::Hidden);
124
125static cl::opt<DropTestKind>
126 ClDropTypeTests("lowertypetests-drop-type-tests",
127 cl::desc("Simply drop type test sequences"),
128 cl::values(clEnumValN(DropTestKind::None, "none",
129 "Do not drop any type tests"),
130 clEnumValN(DropTestKind::Assume, "assume",
131 "Drop type test assume sequences"),
132 clEnumValN(DropTestKind::All, "all",
133 "Drop all type test sequences")),
134 cl::Hidden, cl::init(Val: DropTestKind::None));
135
136bool BitSetInfo::containsGlobalOffset(uint64_t Offset) const {
137 if (Offset < ByteOffset)
138 return false;
139
140 if ((Offset - ByteOffset) % (uint64_t(1) << AlignLog2) != 0)
141 return false;
142
143 uint64_t BitOffset = (Offset - ByteOffset) >> AlignLog2;
144 if (BitOffset >= BitSize)
145 return false;
146
147 return Bits.count(x: BitSize - 1 - BitOffset);
148}
149
150void BitSetInfo::print(raw_ostream &OS) const {
151 OS << "offset " << ByteOffset << " size " << BitSize << " align "
152 << (1 << AlignLog2);
153
154 if (isAllOnes()) {
155 OS << " all-ones\n";
156 return;
157 }
158
159 OS << " { ";
160 for (uint64_t B : Bits)
161 OS << B << ' ';
162 OS << "}\n";
163}
164
165BitSetInfo BitSetBuilder::build() {
166 if (Min > Max)
167 Min = 0;
168
169 // Normalize each offset against the minimum observed offset, and compute
170 // the bitwise OR of each of the offsets. The number of trailing zeros
171 // in the mask gives us the log2 of the alignment of all offsets, which
172 // allows us to compress the bitset by only storing one bit per aligned
173 // address.
174 uint64_t Mask = 0;
175 for (uint64_t &Offset : Offsets) {
176 Offset -= Min;
177 Mask |= Offset;
178 }
179
180 BitSetInfo BSI;
181 BSI.ByteOffset = Min;
182
183 BSI.AlignLog2 = 0;
184 if (Mask != 0)
185 BSI.AlignLog2 = llvm::countr_zero(Val: Mask);
186
187 // Build the compressed bitset while normalizing the offsets against the
188 // computed alignment.
189 BSI.BitSize = ((Max - Min) >> BSI.AlignLog2) + 1;
190 for (uint64_t Offset : Offsets) {
191 Offset >>= BSI.AlignLog2;
192 // We invert the order of bits when adding them to the bitset. This is
193 // because the offset that we test against is computed by subtracting the
194 // address that we are testing from the global's address, which means that
195 // the offset increases as the tested address decreases.
196 BSI.Bits.insert(x: BSI.BitSize - 1 - Offset);
197 }
198
199 return BSI;
200}
201
202void GlobalLayoutBuilder::addFragment(const std::set<uint64_t> &F) {
203 // Create a new fragment to hold the layout for F.
204 Fragments.emplace_back();
205 std::vector<uint64_t> &Fragment = Fragments.back();
206 uint64_t FragmentIndex = Fragments.size() - 1;
207
208 for (auto ObjIndex : F) {
209 uint64_t OldFragmentIndex = FragmentMap[ObjIndex];
210 if (OldFragmentIndex == 0) {
211 // We haven't seen this object index before, so just add it to the current
212 // fragment.
213 Fragment.push_back(x: ObjIndex);
214 } else {
215 // This index belongs to an existing fragment. Copy the elements of the
216 // old fragment into this one and clear the old fragment. We don't update
217 // the fragment map just yet, this ensures that any further references to
218 // indices from the old fragment in this fragment do not insert any more
219 // indices.
220 std::vector<uint64_t> &OldFragment = Fragments[OldFragmentIndex];
221 llvm::append_range(C&: Fragment, R&: OldFragment);
222 OldFragment.clear();
223 }
224 }
225
226 // Update the fragment map to point our object indices to this fragment.
227 for (uint64_t ObjIndex : Fragment)
228 FragmentMap[ObjIndex] = FragmentIndex;
229}
230
231void ByteArrayBuilder::allocate(const std::set<uint64_t> &Bits,
232 uint64_t BitSize, uint64_t &AllocByteOffset,
233 uint8_t &AllocMask) {
234 // Find the smallest current allocation.
235 unsigned Bit = 0;
236 for (unsigned I = 1; I != BitsPerByte; ++I)
237 if (BitAllocs[I] < BitAllocs[Bit])
238 Bit = I;
239
240 AllocByteOffset = BitAllocs[Bit];
241
242 // Add our size to it.
243 unsigned ReqSize = AllocByteOffset + BitSize;
244 BitAllocs[Bit] = ReqSize;
245 if (Bytes.size() < ReqSize)
246 Bytes.resize(new_size: ReqSize);
247
248 // Set our bits.
249 AllocMask = 1 << Bit;
250 for (uint64_t B : Bits)
251 Bytes[AllocByteOffset + B] |= AllocMask;
252}
253
254bool lowertypetests::isJumpTableCanonical(Function *F) {
255 if (F->isDeclarationForLinker())
256 return false;
257 auto *CI = mdconst::extract_or_null<ConstantInt>(
258 MD: F->getParent()->getModuleFlag(Key: "CFI Canonical Jump Tables"));
259 if (!CI || !CI->isZero())
260 return true;
261 return F->hasFnAttribute(Kind: "cfi-canonical-jump-table");
262}
263
264namespace {
265
266struct ByteArrayInfo {
267 std::set<uint64_t> Bits;
268 uint64_t BitSize;
269 GlobalVariable *ByteArray;
270 GlobalVariable *MaskGlobal;
271 uint8_t *MaskPtr = nullptr;
272};
273
274/// A POD-like structure that we use to store a global reference together with
275/// its metadata types. In this pass we frequently need to query the set of
276/// metadata types referenced by a global, which at the IR level is an expensive
277/// operation involving a map lookup; this data structure helps to reduce the
278/// number of times we need to do this lookup.
279class GlobalTypeMember final : TrailingObjects<GlobalTypeMember, MDNode *> {
280 friend TrailingObjects;
281
282 GlobalObject *GO;
283 size_t NTypes;
284
285 // For functions: true if the jump table is canonical. This essentially means
286 // whether the canonical address (i.e. the symbol table entry) of the function
287 // is provided by the local jump table. This is normally the same as whether
288 // the function is defined locally, but if canonical jump tables are disabled
289 // by the user then the jump table never provides a canonical definition.
290 bool IsJumpTableCanonical;
291
292 // For functions: true if this function is either defined or used in a thinlto
293 // module and its jumptable entry needs to be exported to thinlto backends.
294 bool IsExported;
295
296public:
297 static GlobalTypeMember *create(BumpPtrAllocator &Alloc, GlobalObject *GO,
298 bool IsJumpTableCanonical, bool IsExported,
299 ArrayRef<MDNode *> Types) {
300 auto *GTM = static_cast<GlobalTypeMember *>(Alloc.Allocate(
301 Size: totalSizeToAlloc<MDNode *>(Counts: Types.size()), Alignment: alignof(GlobalTypeMember)));
302 GTM->GO = GO;
303 GTM->NTypes = Types.size();
304 GTM->IsJumpTableCanonical = IsJumpTableCanonical;
305 GTM->IsExported = IsExported;
306 llvm::copy(Range&: Types, Out: GTM->getTrailingObjects());
307 return GTM;
308 }
309
310 GlobalObject *getGlobal() const {
311 return GO;
312 }
313
314 bool isJumpTableCanonical() const {
315 return IsJumpTableCanonical;
316 }
317
318 bool isExported() const {
319 return IsExported;
320 }
321
322 ArrayRef<MDNode *> types() const { return getTrailingObjects(N: NTypes); }
323};
324
325struct ICallBranchFunnel final
326 : TrailingObjects<ICallBranchFunnel, GlobalTypeMember *> {
327 static ICallBranchFunnel *create(BumpPtrAllocator &Alloc, CallInst *CI,
328 ArrayRef<GlobalTypeMember *> Targets,
329 unsigned UniqueId) {
330 auto *Call = static_cast<ICallBranchFunnel *>(
331 Alloc.Allocate(Size: totalSizeToAlloc<GlobalTypeMember *>(Counts: Targets.size()),
332 Alignment: alignof(ICallBranchFunnel)));
333 Call->CI = CI;
334 Call->UniqueId = UniqueId;
335 Call->NTargets = Targets.size();
336 llvm::copy(Range&: Targets, Out: Call->getTrailingObjects());
337 return Call;
338 }
339
340 CallInst *CI;
341 ArrayRef<GlobalTypeMember *> targets() const {
342 return getTrailingObjects(N: NTargets);
343 }
344
345 unsigned UniqueId;
346
347private:
348 size_t NTargets;
349};
350
351struct ScopedSaveAliaseesAndUsed {
352 Module &M;
353 SmallVector<GlobalValue *, 4> Used, CompilerUsed;
354 std::vector<std::pair<GlobalAlias *, Function *>> FunctionAliases;
355 std::vector<std::pair<GlobalIFunc *, Function *>> ResolverIFuncs;
356
357 // This function only removes functions from llvm.used and llvm.compiler.used.
358 // We cannot remove global variables because they need to follow RAUW, as
359 // they may be deleted by buildBitSetsFromGlobalVariables.
360 void collectAndEraseUsedFunctions(Module &M,
361 SmallVectorImpl<GlobalValue *> &Vec,
362 bool CompilerUsed) {
363 auto *GV = collectUsedGlobalVariables(M, Vec, CompilerUsed);
364 if (!GV)
365 return;
366 // There's no API to only remove certain array elements from
367 // llvm.used/llvm.compiler.used, so we remove all of them and add back only
368 // the non-functions.
369 GV->eraseFromParent();
370 auto NonFuncBegin =
371 std::stable_partition(first: Vec.begin(), last: Vec.end(), pred: [](GlobalValue *GV) {
372 return isa<Function>(Val: GV);
373 });
374 if (CompilerUsed)
375 appendToCompilerUsed(M, Values: {NonFuncBegin, Vec.end()});
376 else
377 appendToUsed(M, Values: {NonFuncBegin, Vec.end()});
378 Vec.resize(N: NonFuncBegin - Vec.begin());
379 }
380
381 ScopedSaveAliaseesAndUsed(Module &M) : M(M) {
382 // The users of this class want to replace all function references except
383 // for aliases and llvm.used/llvm.compiler.used with references to a jump
384 // table. We avoid replacing aliases in order to avoid introducing a double
385 // indirection (or an alias pointing to a declaration in ThinLTO mode), and
386 // we avoid replacing llvm.used/llvm.compiler.used because these global
387 // variables describe properties of the global, not the jump table (besides,
388 // offseted references to the jump table in llvm.used are invalid).
389 // Unfortunately, LLVM doesn't have a "RAUW except for these (possibly
390 // indirect) users", so what we do is save the list of globals referenced by
391 // llvm.used/llvm.compiler.used and aliases, erase the used lists, let RAUW
392 // replace the aliasees and then set them back to their original values at
393 // the end.
394 collectAndEraseUsedFunctions(M, Vec&: Used, CompilerUsed: false);
395 collectAndEraseUsedFunctions(M, Vec&: CompilerUsed, CompilerUsed: true);
396
397 for (auto &GA : M.aliases()) {
398 // FIXME: This should look past all aliases not just interposable ones,
399 // see discussion on D65118.
400 if (auto *F = dyn_cast<Function>(Val: GA.getAliasee()->stripPointerCasts()))
401 FunctionAliases.push_back(x: {&GA, F});
402 }
403
404 for (auto &GI : M.ifuncs())
405 if (auto *F = dyn_cast<Function>(Val: GI.getResolver()->stripPointerCasts()))
406 ResolverIFuncs.push_back(x: {&GI, F});
407 }
408
409 ~ScopedSaveAliaseesAndUsed() {
410 appendToUsed(M, Values: Used);
411 appendToCompilerUsed(M, Values: CompilerUsed);
412
413 for (auto P : FunctionAliases)
414 P.first->setAliasee(P.second);
415
416 for (auto P : ResolverIFuncs) {
417 // This does not preserve pointer casts that may have been stripped by the
418 // constructor, but the resolver's type is different from that of the
419 // ifunc anyway.
420 P.first->setResolver(P.second);
421 }
422 }
423};
424
425class LowerTypeTestsModule {
426 Module &M;
427
428 ModuleSummaryIndex *ExportSummary;
429 const ModuleSummaryIndex *ImportSummary;
430 // Set when the client has invoked this to simply drop all type test assume
431 // sequences.
432 DropTestKind DropTypeTests;
433
434 Triple::ArchType Arch;
435 Triple::OSType OS;
436 Triple::ObjectFormatType ObjectFormat;
437
438 // Determines which kind of Thumb jump table we generate. If arch is
439 // either 'arm' or 'thumb' we need to find this out, because
440 // selectJumpTableArmEncoding may decide to use Thumb in either case.
441 bool CanUseArmJumpTable = false, CanUseThumbBWJumpTable = false;
442
443 // Cache variable used by hasBranchTargetEnforcement().
444 int HasBranchTargetEnforcement = -1;
445
446 IntegerType *Int1Ty = Type::getInt1Ty(C&: M.getContext());
447 IntegerType *Int8Ty = Type::getInt8Ty(C&: M.getContext());
448 PointerType *PtrTy = PointerType::getUnqual(C&: M.getContext());
449 ArrayType *Int8Arr0Ty = ArrayType::get(ElementType: Type::getInt8Ty(C&: M.getContext()), NumElements: 0);
450 IntegerType *Int32Ty = Type::getInt32Ty(C&: M.getContext());
451 IntegerType *Int64Ty = Type::getInt64Ty(C&: M.getContext());
452 IntegerType *IntPtrTy = M.getDataLayout().getIntPtrType(C&: M.getContext(), AddressSpace: 0);
453
454 // Indirect function call index assignment counter for WebAssembly
455 uint64_t IndirectIndex = 1;
456
457 // Mapping from type identifiers to the call sites that test them, as well as
458 // whether the type identifier needs to be exported to ThinLTO backends as
459 // part of the regular LTO phase of the ThinLTO pipeline (see exportTypeId).
460 struct TypeIdUserInfo {
461 std::vector<CallInst *> CallSites;
462 bool IsExported = false;
463 };
464 DenseMap<Metadata *, TypeIdUserInfo> TypeIdUsers;
465
466 /// This structure describes how to lower type tests for a particular type
467 /// identifier. It is either built directly from the global analysis (during
468 /// regular LTO or the regular LTO phase of ThinLTO), or indirectly using type
469 /// identifier summaries and external symbol references (in ThinLTO backends).
470 struct TypeIdLowering {
471 TypeTestResolution::Kind TheKind = TypeTestResolution::Unsat;
472
473 /// All except Unsat: the address of the last element within the combined
474 /// global.
475 Constant *OffsetedGlobal;
476
477 /// ByteArray, Inline, AllOnes: log2 of the required global alignment
478 /// relative to the start address.
479 Constant *AlignLog2;
480
481 /// ByteArray, Inline, AllOnes: one less than the size of the memory region
482 /// covering members of this type identifier as a multiple of 2^AlignLog2.
483 Constant *SizeM1;
484
485 /// ByteArray: the byte array to test the address against.
486 Constant *TheByteArray;
487
488 /// ByteArray: the bit mask to apply to bytes loaded from the byte array.
489 Constant *BitMask;
490
491 /// Inline: the bit mask to test the address against.
492 Constant *InlineBits;
493 };
494
495 std::vector<ByteArrayInfo> ByteArrayInfos;
496
497 Function *WeakInitializerFn = nullptr;
498
499 GlobalVariable *GlobalAnnotation;
500 DenseSet<Value *> FunctionAnnotations;
501
502 bool shouldExportConstantsAsAbsoluteSymbols();
503 uint8_t *exportTypeId(StringRef TypeId, const TypeIdLowering &TIL);
504 TypeIdLowering importTypeId(StringRef TypeId);
505 void importTypeTest(CallInst *CI);
506 void importFunction(Function *F, bool isJumpTableCanonical);
507
508 ByteArrayInfo *createByteArray(const BitSetInfo &BSI);
509 void allocateByteArrays();
510 Value *createBitSetTest(IRBuilder<> &B, const TypeIdLowering &TIL,
511 Value *BitOffset);
512 void lowerTypeTestCalls(
513 ArrayRef<Metadata *> TypeIds, Constant *CombinedGlobalAddr,
514 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout);
515 Value *lowerTypeTestCall(Metadata *TypeId, CallInst *CI,
516 const TypeIdLowering &TIL);
517
518 void buildBitSetsFromGlobalVariables(ArrayRef<Metadata *> TypeIds,
519 ArrayRef<GlobalTypeMember *> Globals);
520 Triple::ArchType
521 selectJumpTableArmEncoding(ArrayRef<GlobalTypeMember *> Functions);
522 bool hasBranchTargetEnforcement();
523 unsigned getJumpTableEntrySize(Triple::ArchType JumpTableArch);
524 InlineAsm *createJumpTableEntryAsm(Triple::ArchType JumpTableArch);
525 void verifyTypeMDNode(GlobalObject *GO, MDNode *Type);
526 void buildBitSetsFromFunctions(ArrayRef<Metadata *> TypeIds,
527 ArrayRef<GlobalTypeMember *> Functions);
528 void buildBitSetsFromFunctionsNative(ArrayRef<Metadata *> TypeIds,
529 ArrayRef<GlobalTypeMember *> Functions);
530 void buildBitSetsFromFunctionsWASM(ArrayRef<Metadata *> TypeIds,
531 ArrayRef<GlobalTypeMember *> Functions);
532 void
533 buildBitSetsFromDisjointSet(ArrayRef<Metadata *> TypeIds,
534 ArrayRef<GlobalTypeMember *> Globals,
535 ArrayRef<ICallBranchFunnel *> ICallBranchFunnels);
536
537 void replaceWeakDeclarationWithJumpTablePtr(Function *F, Constant *JT,
538 bool IsJumpTableCanonical);
539 void moveInitializerToModuleConstructor(GlobalVariable *GV);
540 void findGlobalVariableUsersOf(Constant *C,
541 SmallSetVector<GlobalVariable *, 8> &Out);
542
543 void createJumpTable(Function *F, ArrayRef<GlobalTypeMember *> Functions,
544 Triple::ArchType JumpTableArch);
545
546 /// replaceCfiUses - Go through the uses list for this definition
547 /// and make each use point to "V" instead of "this" when the use is outside
548 /// the block. 'This's use list is expected to have at least one element.
549 /// Unlike replaceAllUsesWith this function skips blockaddr and direct call
550 /// uses.
551 void replaceCfiUses(Function *Old, Value *New, bool IsJumpTableCanonical);
552
553 /// replaceDirectCalls - Go through the uses list for this definition and
554 /// replace each use, which is a direct function call.
555 void replaceDirectCalls(Value *Old, Value *New);
556
557 bool isFunctionAnnotation(Value *V) const {
558 return FunctionAnnotations.contains(V);
559 }
560
561 void maybeReplaceComdat(Function *F, StringRef OriginalName);
562
563public:
564 LowerTypeTestsModule(Module &M, ModuleAnalysisManager &AM,
565 ModuleSummaryIndex *ExportSummary,
566 const ModuleSummaryIndex *ImportSummary,
567 DropTestKind DropTypeTests);
568
569 bool lower();
570
571 // Lower the module using the action and summary passed as command line
572 // arguments. For testing purposes only.
573 static bool runForTesting(Module &M, ModuleAnalysisManager &AM);
574};
575} // end anonymous namespace
576
577/// Build a bit set for list of offsets.
578static BitSetInfo buildBitSet(ArrayRef<uint64_t> Offsets) {
579 // Compute the byte offset of each address associated with this type
580 // identifier.
581 return BitSetBuilder(Offsets).build();
582}
583
584/// Build a test that bit BitOffset mod sizeof(Bits)*8 is set in
585/// Bits. This pattern matches to the bt instruction on x86.
586static Value *createMaskedBitTest(IRBuilder<> &B, Value *Bits,
587 Value *BitOffset) {
588 auto BitsType = cast<IntegerType>(Val: Bits->getType());
589 unsigned BitWidth = BitsType->getBitWidth();
590
591 BitOffset = B.CreateZExtOrTrunc(V: BitOffset, DestTy: BitsType);
592 Value *BitIndex =
593 B.CreateAnd(LHS: BitOffset, RHS: ConstantInt::get(Ty: BitsType, V: BitWidth - 1));
594 Value *BitMask = B.CreateShl(LHS: ConstantInt::get(Ty: BitsType, V: 1), RHS: BitIndex);
595 Value *MaskedBits = B.CreateAnd(LHS: Bits, RHS: BitMask);
596 return B.CreateICmpNE(LHS: MaskedBits, RHS: ConstantInt::get(Ty: BitsType, V: 0));
597}
598
599ByteArrayInfo *LowerTypeTestsModule::createByteArray(const BitSetInfo &BSI) {
600 // Create globals to stand in for byte arrays and masks. These never actually
601 // get initialized, we RAUW and erase them later in allocateByteArrays() once
602 // we know the offset and mask to use.
603 auto ByteArrayGlobal = new GlobalVariable(
604 M, Int8Ty, /*isConstant=*/true, GlobalValue::PrivateLinkage, nullptr);
605 auto MaskGlobal = new GlobalVariable(M, Int8Ty, /*isConstant=*/true,
606 GlobalValue::PrivateLinkage, nullptr);
607
608 ByteArrayInfos.emplace_back();
609 ByteArrayInfo *BAI = &ByteArrayInfos.back();
610
611 BAI->Bits = BSI.Bits;
612 BAI->BitSize = BSI.BitSize;
613 BAI->ByteArray = ByteArrayGlobal;
614 BAI->MaskGlobal = MaskGlobal;
615 return BAI;
616}
617
618void LowerTypeTestsModule::allocateByteArrays() {
619 llvm::stable_sort(Range&: ByteArrayInfos,
620 C: [](const ByteArrayInfo &BAI1, const ByteArrayInfo &BAI2) {
621 return BAI1.BitSize > BAI2.BitSize;
622 });
623
624 std::vector<uint64_t> ByteArrayOffsets(ByteArrayInfos.size());
625
626 ByteArrayBuilder BAB;
627 for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) {
628 ByteArrayInfo *BAI = &ByteArrayInfos[I];
629
630 uint8_t Mask;
631 BAB.allocate(Bits: BAI->Bits, BitSize: BAI->BitSize, AllocByteOffset&: ByteArrayOffsets[I], AllocMask&: Mask);
632
633 BAI->MaskGlobal->replaceAllUsesWith(
634 V: ConstantExpr::getIntToPtr(C: ConstantInt::get(Ty: Int8Ty, V: Mask), Ty: PtrTy));
635 BAI->MaskGlobal->eraseFromParent();
636 if (BAI->MaskPtr)
637 *BAI->MaskPtr = Mask;
638 }
639
640 Constant *ByteArrayConst = ConstantDataArray::get(Context&: M.getContext(), Elts&: BAB.Bytes);
641 auto ByteArray =
642 new GlobalVariable(M, ByteArrayConst->getType(), /*isConstant=*/true,
643 GlobalValue::PrivateLinkage, ByteArrayConst);
644
645 for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) {
646 ByteArrayInfo *BAI = &ByteArrayInfos[I];
647 Constant *GEP = ConstantExpr::getInBoundsPtrAdd(
648 Ptr: ByteArray, Offset: ConstantInt::get(Ty: IntPtrTy, V: ByteArrayOffsets[I]));
649
650 // Create an alias instead of RAUW'ing the gep directly. On x86 this ensures
651 // that the pc-relative displacement is folded into the lea instead of the
652 // test instruction getting another displacement.
653 GlobalAlias *Alias = GlobalAlias::create(
654 Ty: Int8Ty, AddressSpace: 0, Linkage: GlobalValue::PrivateLinkage, Name: "bits", Aliasee: GEP, Parent: &M);
655 BAI->ByteArray->replaceAllUsesWith(V: Alias);
656 BAI->ByteArray->eraseFromParent();
657 }
658
659 ByteArraySizeBits = BAB.BitAllocs[0] + BAB.BitAllocs[1] + BAB.BitAllocs[2] +
660 BAB.BitAllocs[3] + BAB.BitAllocs[4] + BAB.BitAllocs[5] +
661 BAB.BitAllocs[6] + BAB.BitAllocs[7];
662 ByteArraySizeBytes = BAB.Bytes.size();
663}
664
665/// Build a test that bit BitOffset is set in the type identifier that was
666/// lowered to TIL, which must be either an Inline or a ByteArray.
667Value *LowerTypeTestsModule::createBitSetTest(IRBuilder<> &B,
668 const TypeIdLowering &TIL,
669 Value *BitOffset) {
670 if (TIL.TheKind == TypeTestResolution::Inline) {
671 // If the bit set is sufficiently small, we can avoid a load by bit testing
672 // a constant.
673 return createMaskedBitTest(B, Bits: TIL.InlineBits, BitOffset);
674 } else {
675 Constant *ByteArray = TIL.TheByteArray;
676 if (AvoidReuse && !ImportSummary) {
677 // Each use of the byte array uses a different alias. This makes the
678 // backend less likely to reuse previously computed byte array addresses,
679 // improving the security of the CFI mechanism based on this pass.
680 // This won't work when importing because TheByteArray is external.
681 ByteArray = GlobalAlias::create(Ty: Int8Ty, AddressSpace: 0, Linkage: GlobalValue::PrivateLinkage,
682 Name: "bits_use", Aliasee: ByteArray, Parent: &M);
683 }
684
685 Value *ByteAddr = B.CreateGEP(Ty: Int8Ty, Ptr: ByteArray, IdxList: BitOffset);
686 Value *Byte = B.CreateLoad(Ty: Int8Ty, Ptr: ByteAddr);
687
688 Value *ByteAndMask =
689 B.CreateAnd(LHS: Byte, RHS: ConstantExpr::getPtrToInt(C: TIL.BitMask, Ty: Int8Ty));
690 return B.CreateICmpNE(LHS: ByteAndMask, RHS: ConstantInt::get(Ty: Int8Ty, V: 0));
691 }
692}
693
694static bool isKnownTypeIdMember(Metadata *TypeId, const DataLayout &DL,
695 Value *V, uint64_t COffset) {
696 if (auto GV = dyn_cast<GlobalObject>(Val: V)) {
697 SmallVector<MDNode *, 2> Types;
698 GV->getMetadata(KindID: LLVMContext::MD_type, MDs&: Types);
699 for (MDNode *Type : Types) {
700 if (Type->getOperand(I: 1) != TypeId)
701 continue;
702 uint64_t Offset =
703 cast<ConstantInt>(
704 Val: cast<ConstantAsMetadata>(Val: Type->getOperand(I: 0))->getValue())
705 ->getZExtValue();
706 if (COffset == Offset)
707 return true;
708 }
709 return false;
710 }
711
712 if (auto GEP = dyn_cast<GEPOperator>(Val: V)) {
713 APInt APOffset(DL.getIndexSizeInBits(AS: 0), 0);
714 bool Result = GEP->accumulateConstantOffset(DL, Offset&: APOffset);
715 if (!Result)
716 return false;
717 COffset += APOffset.getZExtValue();
718 return isKnownTypeIdMember(TypeId, DL, V: GEP->getPointerOperand(), COffset);
719 }
720
721 if (auto Op = dyn_cast<Operator>(Val: V)) {
722 if (Op->getOpcode() == Instruction::BitCast)
723 return isKnownTypeIdMember(TypeId, DL, V: Op->getOperand(i: 0), COffset);
724
725 if (Op->getOpcode() == Instruction::Select)
726 return isKnownTypeIdMember(TypeId, DL, V: Op->getOperand(i: 1), COffset) &&
727 isKnownTypeIdMember(TypeId, DL, V: Op->getOperand(i: 2), COffset);
728 }
729
730 return false;
731}
732
733/// Lower a llvm.type.test call to its implementation. Returns the value to
734/// replace the call with.
735Value *LowerTypeTestsModule::lowerTypeTestCall(Metadata *TypeId, CallInst *CI,
736 const TypeIdLowering &TIL) {
737 // Delay lowering if the resolution is currently unknown.
738 if (TIL.TheKind == TypeTestResolution::Unknown)
739 return nullptr;
740 if (TIL.TheKind == TypeTestResolution::Unsat)
741 return ConstantInt::getFalse(Context&: M.getContext());
742
743 Value *Ptr = CI->getArgOperand(i: 0);
744 const DataLayout &DL = M.getDataLayout();
745 if (isKnownTypeIdMember(TypeId, DL, V: Ptr, COffset: 0))
746 return ConstantInt::getTrue(Context&: M.getContext());
747
748 BasicBlock *InitialBB = CI->getParent();
749
750 IRBuilder<> B(CI);
751
752 Value *PtrAsInt = B.CreatePtrToInt(V: Ptr, DestTy: IntPtrTy);
753
754 Constant *OffsetedGlobalAsInt =
755 ConstantExpr::getPtrToInt(C: TIL.OffsetedGlobal, Ty: IntPtrTy);
756 if (TIL.TheKind == TypeTestResolution::Single)
757 return B.CreateICmpEQ(LHS: PtrAsInt, RHS: OffsetedGlobalAsInt);
758
759 // Here we compute `last element - address`. The reason why we do this instead
760 // of computing `address - first element` is that it leads to a slightly
761 // shorter instruction sequence on x86. Because it doesn't matter how we do
762 // the subtraction on other architectures, we do so unconditionally.
763 Value *PtrOffset = B.CreateSub(LHS: OffsetedGlobalAsInt, RHS: PtrAsInt);
764
765 // We need to check that the offset both falls within our range and is
766 // suitably aligned. We can check both properties at the same time by
767 // performing a right rotate by log2(alignment) followed by an integer
768 // comparison against the bitset size. The rotate will move the lower
769 // order bits that need to be zero into the higher order bits of the
770 // result, causing the comparison to fail if they are nonzero. The rotate
771 // also conveniently gives us a bit offset to use during the load from
772 // the bitset.
773 Value *BitOffset = B.CreateIntrinsic(RetTy: IntPtrTy, ID: Intrinsic::fshr,
774 Args: {PtrOffset, PtrOffset, TIL.AlignLog2});
775
776 Value *OffsetInRange = B.CreateICmpULE(LHS: BitOffset, RHS: TIL.SizeM1);
777
778 // If the bit set is all ones, testing against it is unnecessary.
779 if (TIL.TheKind == TypeTestResolution::AllOnes)
780 return OffsetInRange;
781
782 // See if the intrinsic is used in the following common pattern:
783 // br(llvm.type.test(...), thenbb, elsebb)
784 // where nothing happens between the type test and the br.
785 // If so, create slightly simpler IR.
786 if (CI->hasOneUse())
787 if (auto *Br = dyn_cast<BranchInst>(Val: *CI->user_begin()))
788 if (CI->getNextNode() == Br) {
789 BasicBlock *Then = InitialBB->splitBasicBlock(I: CI->getIterator());
790 BasicBlock *Else = Br->getSuccessor(i: 1);
791 BranchInst *NewBr = BranchInst::Create(IfTrue: Then, IfFalse: Else, Cond: OffsetInRange);
792 NewBr->setMetadata(KindID: LLVMContext::MD_prof,
793 Node: Br->getMetadata(KindID: LLVMContext::MD_prof));
794 ReplaceInstWithInst(From: InitialBB->getTerminator(), To: NewBr);
795
796 // Update phis in Else resulting from InitialBB being split
797 for (auto &Phi : Else->phis())
798 Phi.addIncoming(V: Phi.getIncomingValueForBlock(BB: Then), BB: InitialBB);
799
800 IRBuilder<> ThenB(CI);
801 return createBitSetTest(B&: ThenB, TIL, BitOffset);
802 }
803
804 MDBuilder MDB(M.getContext());
805 IRBuilder<> ThenB(SplitBlockAndInsertIfThen(Cond: OffsetInRange, SplitBefore: CI, Unreachable: false,
806 BranchWeights: MDB.createLikelyBranchWeights()));
807
808 // Now that we know that the offset is in range and aligned, load the
809 // appropriate bit from the bitset.
810 Value *Bit = createBitSetTest(B&: ThenB, TIL, BitOffset);
811
812 // The value we want is 0 if we came directly from the initial block
813 // (having failed the range or alignment checks), or the loaded bit if
814 // we came from the block in which we loaded it.
815 B.SetInsertPoint(CI);
816 PHINode *P = B.CreatePHI(Ty: Int1Ty, NumReservedValues: 2);
817 P->addIncoming(V: ConstantInt::get(Ty: Int1Ty, V: 0), BB: InitialBB);
818 P->addIncoming(V: Bit, BB: ThenB.GetInsertBlock());
819 return P;
820}
821
822/// Given a disjoint set of type identifiers and globals, lay out the globals,
823/// build the bit sets and lower the llvm.type.test calls.
824void LowerTypeTestsModule::buildBitSetsFromGlobalVariables(
825 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Globals) {
826 // Build a new global with the combined contents of the referenced globals.
827 // This global is a struct whose even-indexed elements contain the original
828 // contents of the referenced globals and whose odd-indexed elements contain
829 // any padding required to align the next element to the next power of 2 plus
830 // any additional padding required to meet its alignment requirements.
831 std::vector<Constant *> GlobalInits;
832 const DataLayout &DL = M.getDataLayout();
833 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout;
834 Align MaxAlign;
835 uint64_t CurOffset = 0;
836 uint64_t DesiredPadding = 0;
837 for (GlobalTypeMember *G : Globals) {
838 auto *GV = cast<GlobalVariable>(Val: G->getGlobal());
839 Align Alignment =
840 DL.getValueOrABITypeAlignment(Alignment: GV->getAlign(), Ty: GV->getValueType());
841 MaxAlign = std::max(a: MaxAlign, b: Alignment);
842 uint64_t GVOffset = alignTo(Size: CurOffset + DesiredPadding, A: Alignment);
843 GlobalLayout[G] = GVOffset;
844 if (GVOffset != 0) {
845 uint64_t Padding = GVOffset - CurOffset;
846 GlobalInits.push_back(
847 x: ConstantAggregateZero::get(Ty: ArrayType::get(ElementType: Int8Ty, NumElements: Padding)));
848 }
849
850 GlobalInits.push_back(x: GV->getInitializer());
851 uint64_t InitSize = GV->getGlobalSize(DL);
852 CurOffset = GVOffset + InitSize;
853
854 // Compute the amount of padding that we'd like for the next element.
855 DesiredPadding = NextPowerOf2(A: InitSize - 1) - InitSize;
856
857 // Experiments of different caps with Chromium on both x64 and ARM64
858 // have shown that the 32-byte cap generates the smallest binary on
859 // both platforms while different caps yield similar performance.
860 // (see https://lists.llvm.org/pipermail/llvm-dev/2018-July/124694.html)
861 if (DesiredPadding > 32)
862 DesiredPadding = alignTo(Value: InitSize, Align: 32) - InitSize;
863 }
864
865 Constant *NewInit = ConstantStruct::getAnon(Ctx&: M.getContext(), V: GlobalInits);
866 auto *CombinedGlobal =
867 new GlobalVariable(M, NewInit->getType(), /*isConstant=*/true,
868 GlobalValue::PrivateLinkage, NewInit);
869 CombinedGlobal->setAlignment(MaxAlign);
870
871 StructType *NewTy = cast<StructType>(Val: NewInit->getType());
872 lowerTypeTestCalls(TypeIds, CombinedGlobalAddr: CombinedGlobal, GlobalLayout);
873
874 // Build aliases pointing to offsets into the combined global for each
875 // global from which we built the combined global, and replace references
876 // to the original globals with references to the aliases.
877 for (unsigned I = 0; I != Globals.size(); ++I) {
878 GlobalVariable *GV = cast<GlobalVariable>(Val: Globals[I]->getGlobal());
879
880 // Multiply by 2 to account for padding elements.
881 Constant *CombinedGlobalIdxs[] = {ConstantInt::get(Ty: Int32Ty, V: 0),
882 ConstantInt::get(Ty: Int32Ty, V: I * 2)};
883 Constant *CombinedGlobalElemPtr = ConstantExpr::getInBoundsGetElementPtr(
884 Ty: NewInit->getType(), C: CombinedGlobal, IdxList: CombinedGlobalIdxs);
885 assert(GV->getType()->getAddressSpace() == 0);
886 GlobalAlias *GAlias =
887 GlobalAlias::create(Ty: NewTy->getElementType(N: I * 2), AddressSpace: 0, Linkage: GV->getLinkage(),
888 Name: "", Aliasee: CombinedGlobalElemPtr, Parent: &M);
889 GAlias->setVisibility(GV->getVisibility());
890 GAlias->takeName(V: GV);
891 GV->replaceAllUsesWith(V: GAlias);
892 GV->eraseFromParent();
893 }
894}
895
896bool LowerTypeTestsModule::shouldExportConstantsAsAbsoluteSymbols() {
897 return (Arch == Triple::x86 || Arch == Triple::x86_64) &&
898 ObjectFormat == Triple::ELF;
899}
900
901/// Export the given type identifier so that ThinLTO backends may import it.
902/// Type identifiers are exported by adding coarse-grained information about how
903/// to test the type identifier to the summary, and creating symbols in the
904/// object file (aliases and absolute symbols) containing fine-grained
905/// information about the type identifier.
906///
907/// Returns a pointer to the location in which to store the bitmask, if
908/// applicable.
909uint8_t *LowerTypeTestsModule::exportTypeId(StringRef TypeId,
910 const TypeIdLowering &TIL) {
911 TypeTestResolution &TTRes =
912 ExportSummary->getOrInsertTypeIdSummary(TypeId).TTRes;
913 TTRes.TheKind = TIL.TheKind;
914
915 auto ExportGlobal = [&](StringRef Name, Constant *C) {
916 GlobalAlias *GA =
917 GlobalAlias::create(Ty: Int8Ty, AddressSpace: 0, Linkage: GlobalValue::ExternalLinkage,
918 Name: "__typeid_" + TypeId + "_" + Name, Aliasee: C, Parent: &M);
919 GA->setVisibility(GlobalValue::HiddenVisibility);
920 };
921
922 auto ExportConstant = [&](StringRef Name, uint64_t &Storage, Constant *C) {
923 if (shouldExportConstantsAsAbsoluteSymbols())
924 ExportGlobal(Name, ConstantExpr::getIntToPtr(C, Ty: PtrTy));
925 else
926 Storage = cast<ConstantInt>(Val: C)->getZExtValue();
927 };
928
929 if (TIL.TheKind != TypeTestResolution::Unsat)
930 ExportGlobal("global_addr", TIL.OffsetedGlobal);
931
932 if (TIL.TheKind == TypeTestResolution::ByteArray ||
933 TIL.TheKind == TypeTestResolution::Inline ||
934 TIL.TheKind == TypeTestResolution::AllOnes) {
935 ExportConstant("align", TTRes.AlignLog2, TIL.AlignLog2);
936 ExportConstant("size_m1", TTRes.SizeM1, TIL.SizeM1);
937
938 uint64_t BitSize = cast<ConstantInt>(Val: TIL.SizeM1)->getZExtValue() + 1;
939 if (TIL.TheKind == TypeTestResolution::Inline)
940 TTRes.SizeM1BitWidth = (BitSize <= 32) ? 5 : 6;
941 else
942 TTRes.SizeM1BitWidth = (BitSize <= 128) ? 7 : 32;
943 }
944
945 if (TIL.TheKind == TypeTestResolution::ByteArray) {
946 ExportGlobal("byte_array", TIL.TheByteArray);
947 if (shouldExportConstantsAsAbsoluteSymbols())
948 ExportGlobal("bit_mask", TIL.BitMask);
949 else
950 return &TTRes.BitMask;
951 }
952
953 if (TIL.TheKind == TypeTestResolution::Inline)
954 ExportConstant("inline_bits", TTRes.InlineBits, TIL.InlineBits);
955
956 return nullptr;
957}
958
959LowerTypeTestsModule::TypeIdLowering
960LowerTypeTestsModule::importTypeId(StringRef TypeId) {
961 const TypeIdSummary *TidSummary = ImportSummary->getTypeIdSummary(TypeId);
962 if (!TidSummary)
963 return {}; // Unsat: no globals match this type id.
964 const TypeTestResolution &TTRes = TidSummary->TTRes;
965
966 TypeIdLowering TIL;
967 TIL.TheKind = TTRes.TheKind;
968
969 auto ImportGlobal = [&](StringRef Name) {
970 // Give the global a type of length 0 so that it is not assumed not to alias
971 // with any other global.
972 GlobalVariable *GV = M.getOrInsertGlobal(
973 Name: ("__typeid_" + TypeId + "_" + Name).str(), Ty: Int8Arr0Ty);
974 GV->setVisibility(GlobalValue::HiddenVisibility);
975 return GV;
976 };
977
978 auto ImportConstant = [&](StringRef Name, uint64_t Const, unsigned AbsWidth,
979 Type *Ty) {
980 if (!shouldExportConstantsAsAbsoluteSymbols()) {
981 Constant *C =
982 ConstantInt::get(Ty: isa<IntegerType>(Val: Ty) ? Ty : Int64Ty, V: Const);
983 if (!isa<IntegerType>(Val: Ty))
984 C = ConstantExpr::getIntToPtr(C, Ty);
985 return C;
986 }
987
988 Constant *C = ImportGlobal(Name);
989 auto *GV = cast<GlobalVariable>(Val: C->stripPointerCasts());
990 if (isa<IntegerType>(Val: Ty))
991 C = ConstantExpr::getPtrToInt(C, Ty);
992 if (GV->getMetadata(KindID: LLVMContext::MD_absolute_symbol))
993 return C;
994
995 auto SetAbsRange = [&](uint64_t Min, uint64_t Max) {
996 auto *MinC = ConstantAsMetadata::get(C: ConstantInt::get(Ty: IntPtrTy, V: Min));
997 auto *MaxC = ConstantAsMetadata::get(C: ConstantInt::get(Ty: IntPtrTy, V: Max));
998 GV->setMetadata(KindID: LLVMContext::MD_absolute_symbol,
999 Node: MDNode::get(Context&: M.getContext(), MDs: {MinC, MaxC}));
1000 };
1001 if (AbsWidth == IntPtrTy->getBitWidth()) {
1002 uint64_t AllOnes = IntPtrTy->getBitMask();
1003 SetAbsRange(AllOnes, AllOnes); // Full set.
1004 } else {
1005 SetAbsRange(0, 1ull << AbsWidth);
1006 }
1007 return C;
1008 };
1009
1010 if (TIL.TheKind != TypeTestResolution::Unsat) {
1011 auto *GV = ImportGlobal("global_addr");
1012 // This is either a vtable (in .data.rel.ro) or a jump table (in .text).
1013 // Either way it's expected to be in the low 2 GiB, so set the small code
1014 // model.
1015 //
1016 // For .data.rel.ro, we currently place all such sections in the low 2 GiB
1017 // [1], and for .text the sections are expected to be in the low 2 GiB under
1018 // the small and medium code models [2] and this pass only supports those
1019 // code models (e.g. jump tables use jmp instead of movabs/jmp).
1020 //
1021 // [1]https://github.com/llvm/llvm-project/pull/137742
1022 // [2]https://maskray.me/blog/2023-05-14-relocation-overflow-and-code-models
1023 GV->setCodeModel(CodeModel::Small);
1024 TIL.OffsetedGlobal = GV;
1025 }
1026
1027 if (TIL.TheKind == TypeTestResolution::ByteArray ||
1028 TIL.TheKind == TypeTestResolution::Inline ||
1029 TIL.TheKind == TypeTestResolution::AllOnes) {
1030 TIL.AlignLog2 = ImportConstant("align", TTRes.AlignLog2, 8, IntPtrTy);
1031 TIL.SizeM1 =
1032 ImportConstant("size_m1", TTRes.SizeM1, TTRes.SizeM1BitWidth, IntPtrTy);
1033 }
1034
1035 if (TIL.TheKind == TypeTestResolution::ByteArray) {
1036 TIL.TheByteArray = ImportGlobal("byte_array");
1037 TIL.BitMask = ImportConstant("bit_mask", TTRes.BitMask, 8, PtrTy);
1038 }
1039
1040 if (TIL.TheKind == TypeTestResolution::Inline)
1041 TIL.InlineBits = ImportConstant(
1042 "inline_bits", TTRes.InlineBits, 1 << TTRes.SizeM1BitWidth,
1043 TTRes.SizeM1BitWidth <= 5 ? Int32Ty : Int64Ty);
1044
1045 return TIL;
1046}
1047
1048void LowerTypeTestsModule::importTypeTest(CallInst *CI) {
1049 auto TypeIdMDVal = dyn_cast<MetadataAsValue>(Val: CI->getArgOperand(i: 1));
1050 if (!TypeIdMDVal)
1051 report_fatal_error(reason: "Second argument of llvm.type.test must be metadata");
1052
1053 auto TypeIdStr = dyn_cast<MDString>(Val: TypeIdMDVal->getMetadata());
1054 // If this is a local unpromoted type, which doesn't have a metadata string,
1055 // treat as Unknown and delay lowering, so that we can still utilize it for
1056 // later optimizations.
1057 if (!TypeIdStr)
1058 return;
1059
1060 TypeIdLowering TIL = importTypeId(TypeId: TypeIdStr->getString());
1061 Value *Lowered = lowerTypeTestCall(TypeId: TypeIdStr, CI, TIL);
1062 if (Lowered) {
1063 CI->replaceAllUsesWith(V: Lowered);
1064 CI->eraseFromParent();
1065 }
1066}
1067
1068void LowerTypeTestsModule::maybeReplaceComdat(Function *F,
1069 StringRef OriginalName) {
1070 // For COFF we should also rename the comdat if this function also
1071 // happens to be the key function. Even if the comdat name changes, this
1072 // should still be fine since comdat and symbol resolution happens
1073 // before LTO, so all symbols which would prevail have been selected.
1074 if (F->hasComdat() && ObjectFormat == Triple::COFF &&
1075 F->getComdat()->getName() == OriginalName) {
1076 Comdat *OldComdat = F->getComdat();
1077 Comdat *NewComdat = M.getOrInsertComdat(Name: F->getName());
1078 for (GlobalObject &GO : M.global_objects()) {
1079 if (GO.getComdat() == OldComdat)
1080 GO.setComdat(NewComdat);
1081 }
1082 }
1083}
1084
1085// ThinLTO backend: the function F has a jump table entry; update this module
1086// accordingly. isJumpTableCanonical describes the type of the jump table entry.
1087void LowerTypeTestsModule::importFunction(Function *F,
1088 bool isJumpTableCanonical) {
1089 assert(F->getType()->getAddressSpace() == 0);
1090
1091 GlobalValue::VisibilityTypes Visibility = F->getVisibility();
1092 std::string Name = std::string(F->getName());
1093
1094 if (F->isDeclarationForLinker() && isJumpTableCanonical) {
1095 // Non-dso_local functions may be overriden at run time,
1096 // don't short curcuit them
1097 if (F->isDSOLocal()) {
1098 Function *RealF = Function::Create(Ty: F->getFunctionType(),
1099 Linkage: GlobalValue::ExternalLinkage,
1100 AddrSpace: F->getAddressSpace(),
1101 N: Name + ".cfi", M: &M);
1102 RealF->setVisibility(GlobalVariable::HiddenVisibility);
1103 replaceDirectCalls(Old: F, New: RealF);
1104 }
1105 return;
1106 }
1107
1108 Function *FDecl;
1109 if (!isJumpTableCanonical) {
1110 // Either a declaration of an external function or a reference to a locally
1111 // defined jump table.
1112 FDecl = Function::Create(Ty: F->getFunctionType(), Linkage: GlobalValue::ExternalLinkage,
1113 AddrSpace: F->getAddressSpace(), N: Name + ".cfi_jt", M: &M);
1114 FDecl->setVisibility(GlobalValue::HiddenVisibility);
1115 } else {
1116 F->setName(Name + ".cfi");
1117 maybeReplaceComdat(F, OriginalName: Name);
1118 FDecl = Function::Create(Ty: F->getFunctionType(), Linkage: GlobalValue::ExternalLinkage,
1119 AddrSpace: F->getAddressSpace(), N: Name, M: &M);
1120 FDecl->setVisibility(Visibility);
1121 Visibility = GlobalValue::HiddenVisibility;
1122
1123 // Update aliases pointing to this function to also include the ".cfi" suffix,
1124 // We expect the jump table entry to either point to the real function or an
1125 // alias. Redirect all other users to the jump table entry.
1126 for (auto &U : F->uses()) {
1127 if (auto *A = dyn_cast<GlobalAlias>(Val: U.getUser())) {
1128 std::string AliasName = A->getName().str() + ".cfi";
1129 Function *AliasDecl = Function::Create(
1130 Ty: F->getFunctionType(), Linkage: GlobalValue::ExternalLinkage,
1131 AddrSpace: F->getAddressSpace(), N: "", M: &M);
1132 AliasDecl->takeName(V: A);
1133 A->replaceAllUsesWith(V: AliasDecl);
1134 A->setName(AliasName);
1135 }
1136 }
1137 }
1138
1139 if (F->hasExternalWeakLinkage())
1140 replaceWeakDeclarationWithJumpTablePtr(F, JT: FDecl, IsJumpTableCanonical: isJumpTableCanonical);
1141 else
1142 replaceCfiUses(Old: F, New: FDecl, IsJumpTableCanonical: isJumpTableCanonical);
1143
1144 // Set visibility late because it's used in replaceCfiUses() to determine
1145 // whether uses need to be replaced.
1146 F->setVisibility(Visibility);
1147}
1148
1149static auto
1150buildBitSets(ArrayRef<Metadata *> TypeIds,
1151 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout) {
1152 DenseMap<Metadata *, SmallVector<uint64_t, 16>> OffsetsByTypeID;
1153 // Pre-populate the map with interesting type identifiers.
1154 for (Metadata *TypeId : TypeIds)
1155 OffsetsByTypeID[TypeId];
1156 for (const auto &[Mem, MemOff] : GlobalLayout) {
1157 for (MDNode *Type : Mem->types()) {
1158 auto It = OffsetsByTypeID.find(Val: Type->getOperand(I: 1));
1159 if (It == OffsetsByTypeID.end())
1160 continue;
1161 uint64_t Offset =
1162 cast<ConstantInt>(
1163 Val: cast<ConstantAsMetadata>(Val: Type->getOperand(I: 0))->getValue())
1164 ->getZExtValue();
1165 It->second.push_back(Elt: MemOff + Offset);
1166 }
1167 }
1168
1169 SmallVector<std::pair<Metadata *, BitSetInfo>> BitSets;
1170 BitSets.reserve(N: TypeIds.size());
1171 for (Metadata *TypeId : TypeIds) {
1172 BitSets.emplace_back(Args&: TypeId, Args: buildBitSet(Offsets: OffsetsByTypeID[TypeId]));
1173 LLVM_DEBUG({
1174 if (auto MDS = dyn_cast<MDString>(TypeId))
1175 dbgs() << MDS->getString() << ": ";
1176 else
1177 dbgs() << "<unnamed>: ";
1178 BitSets.back().second.print(dbgs());
1179 });
1180 }
1181
1182 return BitSets;
1183}
1184
1185void LowerTypeTestsModule::lowerTypeTestCalls(
1186 ArrayRef<Metadata *> TypeIds, Constant *CombinedGlobalAddr,
1187 const DenseMap<GlobalTypeMember *, uint64_t> &GlobalLayout) {
1188 // For each type identifier in this disjoint set...
1189 for (const auto &[TypeId, BSI] : buildBitSets(TypeIds, GlobalLayout)) {
1190 ByteArrayInfo *BAI = nullptr;
1191 TypeIdLowering TIL;
1192
1193 uint64_t GlobalOffset =
1194 BSI.ByteOffset + ((BSI.BitSize - 1) << BSI.AlignLog2);
1195 TIL.OffsetedGlobal = ConstantExpr::getPtrAdd(
1196 Ptr: CombinedGlobalAddr, Offset: ConstantInt::get(Ty: IntPtrTy, V: GlobalOffset)),
1197 TIL.AlignLog2 = ConstantInt::get(Ty: IntPtrTy, V: BSI.AlignLog2);
1198 TIL.SizeM1 = ConstantInt::get(Ty: IntPtrTy, V: BSI.BitSize - 1);
1199 if (BSI.isAllOnes()) {
1200 TIL.TheKind = (BSI.BitSize == 1) ? TypeTestResolution::Single
1201 : TypeTestResolution::AllOnes;
1202 } else if (BSI.BitSize <= IntPtrTy->getBitWidth()) {
1203 TIL.TheKind = TypeTestResolution::Inline;
1204 uint64_t InlineBits = 0;
1205 for (auto Bit : BSI.Bits)
1206 InlineBits |= uint64_t(1) << Bit;
1207 if (InlineBits == 0)
1208 TIL.TheKind = TypeTestResolution::Unsat;
1209 else
1210 TIL.InlineBits = ConstantInt::get(
1211 Ty: (BSI.BitSize <= 32) ? Int32Ty : Int64Ty, V: InlineBits);
1212 } else {
1213 TIL.TheKind = TypeTestResolution::ByteArray;
1214 ++NumByteArraysCreated;
1215 BAI = createByteArray(BSI);
1216 TIL.TheByteArray = BAI->ByteArray;
1217 TIL.BitMask = BAI->MaskGlobal;
1218 }
1219
1220 TypeIdUserInfo &TIUI = TypeIdUsers[TypeId];
1221
1222 if (TIUI.IsExported) {
1223 uint8_t *MaskPtr = exportTypeId(TypeId: cast<MDString>(Val: TypeId)->getString(), TIL);
1224 if (BAI)
1225 BAI->MaskPtr = MaskPtr;
1226 }
1227
1228 // Lower each call to llvm.type.test for this type identifier.
1229 for (CallInst *CI : TIUI.CallSites) {
1230 ++NumTypeTestCallsLowered;
1231 Value *Lowered = lowerTypeTestCall(TypeId, CI, TIL);
1232 if (Lowered) {
1233 CI->replaceAllUsesWith(V: Lowered);
1234 CI->eraseFromParent();
1235 }
1236 }
1237 }
1238}
1239
1240void LowerTypeTestsModule::verifyTypeMDNode(GlobalObject *GO, MDNode *Type) {
1241 if (Type->getNumOperands() != 2)
1242 report_fatal_error(reason: "All operands of type metadata must have 2 elements");
1243
1244 if (GO->isThreadLocal())
1245 report_fatal_error(reason: "Bit set element may not be thread-local");
1246 if (isa<GlobalVariable>(Val: GO) && GO->hasSection())
1247 report_fatal_error(
1248 reason: "A member of a type identifier may not have an explicit section");
1249
1250 // FIXME: We previously checked that global var member of a type identifier
1251 // must be a definition, but the IR linker may leave type metadata on
1252 // declarations. We should restore this check after fixing PR31759.
1253
1254 auto OffsetConstMD = dyn_cast<ConstantAsMetadata>(Val: Type->getOperand(I: 0));
1255 if (!OffsetConstMD)
1256 report_fatal_error(reason: "Type offset must be a constant");
1257 auto OffsetInt = dyn_cast<ConstantInt>(Val: OffsetConstMD->getValue());
1258 if (!OffsetInt)
1259 report_fatal_error(reason: "Type offset must be an integer constant");
1260}
1261
1262static const unsigned kX86JumpTableEntrySize = 8;
1263static const unsigned kX86IBTJumpTableEntrySize = 16;
1264static const unsigned kARMJumpTableEntrySize = 4;
1265static const unsigned kARMBTIJumpTableEntrySize = 8;
1266static const unsigned kARMv6MJumpTableEntrySize = 16;
1267static const unsigned kRISCVJumpTableEntrySize = 8;
1268static const unsigned kLOONGARCH64JumpTableEntrySize = 8;
1269
1270bool LowerTypeTestsModule::hasBranchTargetEnforcement() {
1271 if (HasBranchTargetEnforcement == -1) {
1272 // First time this query has been called. Find out the answer by checking
1273 // the module flags.
1274 if (const auto *BTE = mdconst::extract_or_null<ConstantInt>(
1275 MD: M.getModuleFlag(Key: "branch-target-enforcement")))
1276 HasBranchTargetEnforcement = !BTE->isZero();
1277 else
1278 HasBranchTargetEnforcement = 0;
1279 }
1280 return HasBranchTargetEnforcement;
1281}
1282
1283unsigned
1284LowerTypeTestsModule::getJumpTableEntrySize(Triple::ArchType JumpTableArch) {
1285 switch (JumpTableArch) {
1286 case Triple::x86:
1287 case Triple::x86_64:
1288 if (const auto *MD = mdconst::extract_or_null<ConstantInt>(
1289 MD: M.getModuleFlag(Key: "cf-protection-branch")))
1290 if (MD->getZExtValue())
1291 return kX86IBTJumpTableEntrySize;
1292 return kX86JumpTableEntrySize;
1293 case Triple::arm:
1294 return kARMJumpTableEntrySize;
1295 case Triple::thumb:
1296 if (CanUseThumbBWJumpTable) {
1297 if (hasBranchTargetEnforcement())
1298 return kARMBTIJumpTableEntrySize;
1299 return kARMJumpTableEntrySize;
1300 } else {
1301 return kARMv6MJumpTableEntrySize;
1302 }
1303 case Triple::aarch64:
1304 if (hasBranchTargetEnforcement())
1305 return kARMBTIJumpTableEntrySize;
1306 return kARMJumpTableEntrySize;
1307 case Triple::riscv32:
1308 case Triple::riscv64:
1309 return kRISCVJumpTableEntrySize;
1310 case Triple::loongarch64:
1311 return kLOONGARCH64JumpTableEntrySize;
1312 default:
1313 report_fatal_error(reason: "Unsupported architecture for jump tables");
1314 }
1315}
1316
1317// Create an inline asm constant representing a jump table entry for the target.
1318// This consists of an instruction sequence containing a relative branch to
1319// Dest.
1320InlineAsm *
1321LowerTypeTestsModule::createJumpTableEntryAsm(Triple::ArchType JumpTableArch) {
1322 std::string Asm;
1323 raw_string_ostream AsmOS(Asm);
1324
1325 if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64) {
1326 bool Endbr = false;
1327 if (const auto *MD = mdconst::extract_or_null<ConstantInt>(
1328 MD: M.getModuleFlag(Key: "cf-protection-branch")))
1329 Endbr = !MD->isZero();
1330 if (Endbr)
1331 AsmOS << (JumpTableArch == Triple::x86 ? "endbr32\n" : "endbr64\n");
1332 AsmOS << "jmp ${0:c}@plt\n";
1333 if (Endbr)
1334 AsmOS << ".balign 16, 0xcc\n";
1335 else
1336 AsmOS << "int3\nint3\nint3\n";
1337 } else if (JumpTableArch == Triple::arm) {
1338 AsmOS << "b $0\n";
1339 } else if (JumpTableArch == Triple::aarch64) {
1340 if (hasBranchTargetEnforcement())
1341 AsmOS << "bti c\n";
1342 AsmOS << "b $0\n";
1343 } else if (JumpTableArch == Triple::thumb) {
1344 if (!CanUseThumbBWJumpTable) {
1345 // In Armv6-M, this sequence will generate a branch without corrupting
1346 // any registers. We use two stack words; in the second, we construct the
1347 // address we'll pop into pc, and the first is used to save and restore
1348 // r0 which we use as a temporary register.
1349 //
1350 // To support position-independent use cases, the offset of the target
1351 // function is stored as a relative offset (which will expand into an
1352 // R_ARM_REL32 relocation in ELF, and presumably the equivalent in other
1353 // object file types), and added to pc after we load it. (The alternative
1354 // B.W is automatically pc-relative.)
1355 //
1356 // There are five 16-bit Thumb instructions here, so the .balign 4 adds a
1357 // sixth halfword of padding, and then the offset consumes a further 4
1358 // bytes, for a total of 16, which is very convenient since entries in
1359 // this jump table need to have power-of-two size.
1360 AsmOS << "push {r0,r1}\n"
1361 << "ldr r0, 1f\n"
1362 << "0: add r0, r0, pc\n"
1363 << "str r0, [sp, #4]\n"
1364 << "pop {r0,pc}\n"
1365 << ".balign 4\n"
1366 << "1: .word $0 - (0b + 4)\n";
1367 } else {
1368 if (hasBranchTargetEnforcement())
1369 AsmOS << "bti\n";
1370 AsmOS << "b.w $0\n";
1371 }
1372 } else if (JumpTableArch == Triple::riscv32 ||
1373 JumpTableArch == Triple::riscv64) {
1374 AsmOS << "tail $0@plt\n";
1375 } else if (JumpTableArch == Triple::loongarch64) {
1376 AsmOS << "pcalau12i $$t0, %pc_hi20($0)\n"
1377 << "jirl $$r0, $$t0, %pc_lo12($0)\n";
1378 } else {
1379 report_fatal_error(reason: "Unsupported architecture for jump tables");
1380 }
1381
1382 return InlineAsm::get(
1383 Ty: FunctionType::get(Result: Type::getVoidTy(C&: M.getContext()), Params: PtrTy, isVarArg: false),
1384 AsmString: AsmOS.str(), Constraints: "s",
1385 /*hasSideEffects=*/true);
1386}
1387
1388/// Given a disjoint set of type identifiers and functions, build the bit sets
1389/// and lower the llvm.type.test calls, architecture dependently.
1390void LowerTypeTestsModule::buildBitSetsFromFunctions(
1391 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) {
1392 if (Arch == Triple::x86 || Arch == Triple::x86_64 || Arch == Triple::arm ||
1393 Arch == Triple::thumb || Arch == Triple::aarch64 ||
1394 Arch == Triple::riscv32 || Arch == Triple::riscv64 ||
1395 Arch == Triple::loongarch64)
1396 buildBitSetsFromFunctionsNative(TypeIds, Functions);
1397 else if (Arch == Triple::wasm32 || Arch == Triple::wasm64)
1398 buildBitSetsFromFunctionsWASM(TypeIds, Functions);
1399 else
1400 report_fatal_error(reason: "Unsupported architecture for jump tables");
1401}
1402
1403void LowerTypeTestsModule::moveInitializerToModuleConstructor(
1404 GlobalVariable *GV) {
1405 if (WeakInitializerFn == nullptr) {
1406 WeakInitializerFn = Function::Create(
1407 Ty: FunctionType::get(Result: Type::getVoidTy(C&: M.getContext()),
1408 /* IsVarArg */ isVarArg: false),
1409 Linkage: GlobalValue::InternalLinkage,
1410 AddrSpace: M.getDataLayout().getProgramAddressSpace(),
1411 N: "__cfi_global_var_init", M: &M);
1412 BasicBlock *BB =
1413 BasicBlock::Create(Context&: M.getContext(), Name: "entry", Parent: WeakInitializerFn);
1414 ReturnInst::Create(C&: M.getContext(), InsertAtEnd: BB);
1415 WeakInitializerFn->setSection(
1416 ObjectFormat == Triple::MachO
1417 ? "__TEXT,__StaticInit,regular,pure_instructions"
1418 : ".text.startup");
1419 // This code is equivalent to relocation application, and should run at the
1420 // earliest possible time (i.e. with the highest priority).
1421 appendToGlobalCtors(M, F: WeakInitializerFn, /* Priority */ 0);
1422 }
1423
1424 IRBuilder<> IRB(WeakInitializerFn->getEntryBlock().getTerminator());
1425 GV->setConstant(false);
1426 IRB.CreateAlignedStore(Val: GV->getInitializer(), Ptr: GV, Align: GV->getAlign());
1427 GV->setInitializer(Constant::getNullValue(Ty: GV->getValueType()));
1428}
1429
1430void LowerTypeTestsModule::findGlobalVariableUsersOf(
1431 Constant *C, SmallSetVector<GlobalVariable *, 8> &Out) {
1432 for (auto *U : C->users()){
1433 if (auto *GV = dyn_cast<GlobalVariable>(Val: U))
1434 Out.insert(X: GV);
1435 else if (auto *C2 = dyn_cast<Constant>(Val: U))
1436 findGlobalVariableUsersOf(C: C2, Out);
1437 }
1438}
1439
1440// Replace all uses of F with (F ? JT : 0).
1441void LowerTypeTestsModule::replaceWeakDeclarationWithJumpTablePtr(
1442 Function *F, Constant *JT, bool IsJumpTableCanonical) {
1443 // The target expression can not appear in a constant initializer on most
1444 // (all?) targets. Switch to a runtime initializer.
1445 SmallSetVector<GlobalVariable *, 8> GlobalVarUsers;
1446 findGlobalVariableUsersOf(C: F, Out&: GlobalVarUsers);
1447 for (auto *GV : GlobalVarUsers) {
1448 if (GV == GlobalAnnotation)
1449 continue;
1450 moveInitializerToModuleConstructor(GV);
1451 }
1452
1453 // Can not RAUW F with an expression that uses F. Replace with a temporary
1454 // placeholder first.
1455 Function *PlaceholderFn =
1456 Function::Create(Ty: F->getFunctionType(), Linkage: GlobalValue::ExternalWeakLinkage,
1457 AddrSpace: F->getAddressSpace(), N: "", M: &M);
1458 replaceCfiUses(Old: F, New: PlaceholderFn, IsJumpTableCanonical);
1459
1460 convertUsersOfConstantsToInstructions(Consts: PlaceholderFn);
1461 // Don't use range based loop, because use list will be modified.
1462 while (!PlaceholderFn->use_empty()) {
1463 Use &U = *PlaceholderFn->use_begin();
1464 auto *InsertPt = dyn_cast<Instruction>(Val: U.getUser());
1465 assert(InsertPt && "Non-instruction users should have been eliminated");
1466 auto *PN = dyn_cast<PHINode>(Val: InsertPt);
1467 if (PN)
1468 InsertPt = PN->getIncomingBlock(U)->getTerminator();
1469 IRBuilder Builder(InsertPt);
1470 Value *ICmp = Builder.CreateICmp(P: CmpInst::ICMP_NE, LHS: F,
1471 RHS: Constant::getNullValue(Ty: F->getType()));
1472 Value *Select = Builder.CreateSelect(C: ICmp, True: JT,
1473 False: Constant::getNullValue(Ty: F->getType()));
1474
1475 if (auto *SI = dyn_cast<SelectInst>(Val: Select))
1476 setExplicitlyUnknownBranchWeightsIfProfiled(I&: *SI, DEBUG_TYPE);
1477 // For phi nodes, we need to update the incoming value for all operands
1478 // with the same predecessor.
1479 if (PN)
1480 PN->setIncomingValueForBlock(BB: InsertPt->getParent(), V: Select);
1481 else
1482 U.set(Select);
1483 }
1484 PlaceholderFn->eraseFromParent();
1485}
1486
1487static bool isThumbFunction(Function *F, Triple::ArchType ModuleArch) {
1488 Attribute TFAttr = F->getFnAttribute(Kind: "target-features");
1489 if (TFAttr.isValid()) {
1490 SmallVector<StringRef, 6> Features;
1491 TFAttr.getValueAsString().split(A&: Features, Separator: ',');
1492 for (StringRef Feature : Features) {
1493 if (Feature == "-thumb-mode")
1494 return false;
1495 else if (Feature == "+thumb-mode")
1496 return true;
1497 }
1498 }
1499
1500 return ModuleArch == Triple::thumb;
1501}
1502
1503// Each jump table must be either ARM or Thumb as a whole for the bit-test math
1504// to work. Pick one that matches the majority of members to minimize interop
1505// veneers inserted by the linker.
1506Triple::ArchType LowerTypeTestsModule::selectJumpTableArmEncoding(
1507 ArrayRef<GlobalTypeMember *> Functions) {
1508 if (Arch != Triple::arm && Arch != Triple::thumb)
1509 return Arch;
1510
1511 if (!CanUseThumbBWJumpTable && CanUseArmJumpTable) {
1512 // In architectures that provide Arm and Thumb-1 but not Thumb-2,
1513 // we should always prefer the Arm jump table format, because the
1514 // Thumb-1 one is larger and slower.
1515 return Triple::arm;
1516 }
1517
1518 // Otherwise, go with majority vote.
1519 unsigned ArmCount = 0, ThumbCount = 0;
1520 for (const auto GTM : Functions) {
1521 if (!GTM->isJumpTableCanonical()) {
1522 // PLT stubs are always ARM.
1523 // FIXME: This is the wrong heuristic for non-canonical jump tables.
1524 ++ArmCount;
1525 continue;
1526 }
1527
1528 Function *F = cast<Function>(Val: GTM->getGlobal());
1529 ++(isThumbFunction(F, ModuleArch: Arch) ? ThumbCount : ArmCount);
1530 }
1531
1532 return ArmCount > ThumbCount ? Triple::arm : Triple::thumb;
1533}
1534
1535void LowerTypeTestsModule::createJumpTable(
1536 Function *F, ArrayRef<GlobalTypeMember *> Functions,
1537 Triple::ArchType JumpTableArch) {
1538 BasicBlock *BB = BasicBlock::Create(Context&: M.getContext(), Name: "entry", Parent: F);
1539 IRBuilder<> IRB(BB);
1540
1541 InlineAsm *JumpTableAsm = createJumpTableEntryAsm(JumpTableArch);
1542
1543 // Check if all entries have the NoUnwind attribute.
1544 // If all entries have it, we can safely mark the
1545 // cfi.jumptable as NoUnwind, otherwise, direct calls
1546 // to the jump table will not handle exceptions properly
1547 bool areAllEntriesNounwind = true;
1548 for (GlobalTypeMember *GTM : Functions) {
1549 if (!llvm::cast<llvm::Function>(Val: GTM->getGlobal())
1550 ->hasFnAttribute(Kind: llvm::Attribute::NoUnwind)) {
1551 areAllEntriesNounwind = false;
1552 }
1553 IRB.CreateCall(Callee: JumpTableAsm, Args: GTM->getGlobal());
1554 }
1555 IRB.CreateUnreachable();
1556
1557 // Align the whole table by entry size.
1558 F->setAlignment(Align(getJumpTableEntrySize(JumpTableArch)));
1559 F->addFnAttr(Kind: Attribute::Naked);
1560 if (JumpTableArch == Triple::arm)
1561 F->addFnAttr(Kind: "target-features", Val: "-thumb-mode");
1562 if (JumpTableArch == Triple::thumb) {
1563 if (hasBranchTargetEnforcement()) {
1564 // If we're generating a Thumb jump table with BTI, add a target-features
1565 // setting to ensure BTI can be assembled.
1566 F->addFnAttr(Kind: "target-features", Val: "+thumb-mode,+pacbti");
1567 } else {
1568 F->addFnAttr(Kind: "target-features", Val: "+thumb-mode");
1569 if (CanUseThumbBWJumpTable) {
1570 // Thumb jump table assembly needs Thumb2. The following attribute is
1571 // added by Clang for -march=armv7.
1572 F->addFnAttr(Kind: "target-cpu", Val: "cortex-a8");
1573 }
1574 }
1575 }
1576 // When -mbranch-protection= is used, the inline asm adds a BTI. Suppress BTI
1577 // for the function to avoid double BTI. This is a no-op without
1578 // -mbranch-protection=.
1579 if (JumpTableArch == Triple::aarch64 || JumpTableArch == Triple::thumb) {
1580 if (F->hasFnAttribute(Kind: "branch-target-enforcement"))
1581 F->removeFnAttr(Kind: "branch-target-enforcement");
1582 if (F->hasFnAttribute(Kind: "sign-return-address"))
1583 F->removeFnAttr(Kind: "sign-return-address");
1584 }
1585 if (JumpTableArch == Triple::riscv32 || JumpTableArch == Triple::riscv64) {
1586 // Make sure the jump table assembly is not modified by the assembler or
1587 // the linker.
1588 F->addFnAttr(Kind: "target-features", Val: "-c,-relax");
1589 }
1590 // When -fcf-protection= is used, the inline asm adds an ENDBR. Suppress ENDBR
1591 // for the function to avoid double ENDBR. This is a no-op without
1592 // -fcf-protection=.
1593 if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64)
1594 F->addFnAttr(Kind: Attribute::NoCfCheck);
1595
1596 // Make sure we don't emit .eh_frame for this function if it isn't needed.
1597 if (areAllEntriesNounwind)
1598 F->addFnAttr(Kind: Attribute::NoUnwind);
1599
1600 // Make sure we do not inline any calls to the cfi.jumptable.
1601 F->addFnAttr(Kind: Attribute::NoInline);
1602}
1603
1604/// Given a disjoint set of type identifiers and functions, build a jump table
1605/// for the functions, build the bit sets and lower the llvm.type.test calls.
1606void LowerTypeTestsModule::buildBitSetsFromFunctionsNative(
1607 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) {
1608 // Unlike the global bitset builder, the function bitset builder cannot
1609 // re-arrange functions in a particular order and base its calculations on the
1610 // layout of the functions' entry points, as we have no idea how large a
1611 // particular function will end up being (the size could even depend on what
1612 // this pass does!) Instead, we build a jump table, which is a block of code
1613 // consisting of one branch instruction for each of the functions in the bit
1614 // set that branches to the target function, and redirect any taken function
1615 // addresses to the corresponding jump table entry. In the object file's
1616 // symbol table, the symbols for the target functions also refer to the jump
1617 // table entries, so that addresses taken outside the module will pass any
1618 // verification done inside the module.
1619 //
1620 // In more concrete terms, suppose we have three functions f, g, h which are
1621 // of the same type, and a function foo that returns their addresses:
1622 //
1623 // f:
1624 // mov 0, %eax
1625 // ret
1626 //
1627 // g:
1628 // mov 1, %eax
1629 // ret
1630 //
1631 // h:
1632 // mov 2, %eax
1633 // ret
1634 //
1635 // foo:
1636 // mov f, %eax
1637 // mov g, %edx
1638 // mov h, %ecx
1639 // ret
1640 //
1641 // We output the jump table as module-level inline asm string. The end result
1642 // will (conceptually) look like this:
1643 //
1644 // f = .cfi.jumptable
1645 // g = .cfi.jumptable + 4
1646 // h = .cfi.jumptable + 8
1647 // .cfi.jumptable:
1648 // jmp f.cfi ; 5 bytes
1649 // int3 ; 1 byte
1650 // int3 ; 1 byte
1651 // int3 ; 1 byte
1652 // jmp g.cfi ; 5 bytes
1653 // int3 ; 1 byte
1654 // int3 ; 1 byte
1655 // int3 ; 1 byte
1656 // jmp h.cfi ; 5 bytes
1657 // int3 ; 1 byte
1658 // int3 ; 1 byte
1659 // int3 ; 1 byte
1660 //
1661 // f.cfi:
1662 // mov 0, %eax
1663 // ret
1664 //
1665 // g.cfi:
1666 // mov 1, %eax
1667 // ret
1668 //
1669 // h.cfi:
1670 // mov 2, %eax
1671 // ret
1672 //
1673 // foo:
1674 // mov f, %eax
1675 // mov g, %edx
1676 // mov h, %ecx
1677 // ret
1678 //
1679 // Because the addresses of f, g, h are evenly spaced at a power of 2, in the
1680 // normal case the check can be carried out using the same kind of simple
1681 // arithmetic that we normally use for globals.
1682
1683 // FIXME: find a better way to represent the jumptable in the IR.
1684 assert(!Functions.empty());
1685
1686 // Decide on the jump table encoding, so that we know how big the
1687 // entries will be.
1688 Triple::ArchType JumpTableArch = selectJumpTableArmEncoding(Functions);
1689
1690 // Build a simple layout based on the regular layout of jump tables.
1691 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout;
1692 unsigned EntrySize = getJumpTableEntrySize(JumpTableArch);
1693 for (unsigned I = 0; I != Functions.size(); ++I)
1694 GlobalLayout[Functions[I]] = I * EntrySize;
1695
1696 Function *JumpTableFn =
1697 Function::Create(Ty: FunctionType::get(Result: Type::getVoidTy(C&: M.getContext()),
1698 /* IsVarArg */ isVarArg: false),
1699 Linkage: GlobalValue::PrivateLinkage,
1700 AddrSpace: M.getDataLayout().getProgramAddressSpace(),
1701 N: ".cfi.jumptable", M: &M);
1702 ArrayType *JumpTableEntryType = ArrayType::get(ElementType: Int8Ty, NumElements: EntrySize);
1703 ArrayType *JumpTableType =
1704 ArrayType::get(ElementType: JumpTableEntryType, NumElements: Functions.size());
1705 auto JumpTable = ConstantExpr::getPointerCast(
1706 C: JumpTableFn, Ty: PointerType::getUnqual(C&: M.getContext()));
1707
1708 lowerTypeTestCalls(TypeIds, CombinedGlobalAddr: JumpTable, GlobalLayout);
1709
1710 // Build aliases pointing to offsets into the jump table, and replace
1711 // references to the original functions with references to the aliases.
1712 for (unsigned I = 0; I != Functions.size(); ++I) {
1713 Function *F = cast<Function>(Val: Functions[I]->getGlobal());
1714 bool IsJumpTableCanonical = Functions[I]->isJumpTableCanonical();
1715
1716 Constant *CombinedGlobalElemPtr = ConstantExpr::getInBoundsGetElementPtr(
1717 Ty: JumpTableType, C: JumpTable,
1718 IdxList: ArrayRef<Constant *>{ConstantInt::get(Ty: IntPtrTy, V: 0),
1719 ConstantInt::get(Ty: IntPtrTy, V: I)});
1720
1721 const bool IsExported = Functions[I]->isExported();
1722 if (!IsJumpTableCanonical) {
1723 GlobalValue::LinkageTypes LT = IsExported ? GlobalValue::ExternalLinkage
1724 : GlobalValue::InternalLinkage;
1725 GlobalAlias *JtAlias = GlobalAlias::create(Ty: JumpTableEntryType, AddressSpace: 0, Linkage: LT,
1726 Name: F->getName() + ".cfi_jt",
1727 Aliasee: CombinedGlobalElemPtr, Parent: &M);
1728 if (IsExported)
1729 JtAlias->setVisibility(GlobalValue::HiddenVisibility);
1730 else
1731 appendToUsed(M, Values: {JtAlias});
1732 }
1733
1734 if (IsExported) {
1735 if (IsJumpTableCanonical)
1736 ExportSummary->cfiFunctionDefs().emplace(A: F->getName());
1737 else
1738 ExportSummary->cfiFunctionDecls().emplace(A: F->getName());
1739 }
1740
1741 if (!IsJumpTableCanonical) {
1742 if (F->hasExternalWeakLinkage())
1743 replaceWeakDeclarationWithJumpTablePtr(F, JT: CombinedGlobalElemPtr,
1744 IsJumpTableCanonical);
1745 else
1746 replaceCfiUses(Old: F, New: CombinedGlobalElemPtr, IsJumpTableCanonical);
1747 } else {
1748 assert(F->getType()->getAddressSpace() == 0);
1749
1750 GlobalAlias *FAlias =
1751 GlobalAlias::create(Ty: JumpTableEntryType, AddressSpace: 0, Linkage: F->getLinkage(), Name: "",
1752 Aliasee: CombinedGlobalElemPtr, Parent: &M);
1753 FAlias->setVisibility(F->getVisibility());
1754 FAlias->takeName(V: F);
1755 if (FAlias->hasName()) {
1756 F->setName(FAlias->getName() + ".cfi");
1757 maybeReplaceComdat(F, OriginalName: FAlias->getName());
1758 }
1759 replaceCfiUses(Old: F, New: FAlias, IsJumpTableCanonical);
1760 if (!F->hasLocalLinkage())
1761 F->setVisibility(GlobalVariable::HiddenVisibility);
1762 }
1763 }
1764
1765 createJumpTable(F: JumpTableFn, Functions, JumpTableArch);
1766}
1767
1768/// Assign a dummy layout using an incrementing counter, tag each function
1769/// with its index represented as metadata, and lower each type test to an
1770/// integer range comparison. During generation of the indirect function call
1771/// table in the backend, it will assign the given indexes.
1772/// Note: Dynamic linking is not supported, as the WebAssembly ABI has not yet
1773/// been finalized.
1774void LowerTypeTestsModule::buildBitSetsFromFunctionsWASM(
1775 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Functions) {
1776 assert(!Functions.empty());
1777
1778 // Build consecutive monotonic integer ranges for each call target set
1779 DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout;
1780
1781 for (GlobalTypeMember *GTM : Functions) {
1782 Function *F = cast<Function>(Val: GTM->getGlobal());
1783
1784 // Skip functions that are not address taken, to avoid bloating the table
1785 if (!F->hasAddressTaken())
1786 continue;
1787
1788 // Store metadata with the index for each function
1789 MDNode *MD = MDNode::get(Context&: F->getContext(),
1790 MDs: ArrayRef<Metadata *>(ConstantAsMetadata::get(
1791 C: ConstantInt::get(Ty: Int64Ty, V: IndirectIndex))));
1792 F->setMetadata(Kind: "wasm.index", Node: MD);
1793
1794 // Assign the counter value
1795 GlobalLayout[GTM] = IndirectIndex++;
1796 }
1797
1798 // The indirect function table index space starts at zero, so pass a NULL
1799 // pointer as the subtracted "jump table" offset.
1800 lowerTypeTestCalls(TypeIds, CombinedGlobalAddr: ConstantPointerNull::get(T: PtrTy),
1801 GlobalLayout);
1802}
1803
1804void LowerTypeTestsModule::buildBitSetsFromDisjointSet(
1805 ArrayRef<Metadata *> TypeIds, ArrayRef<GlobalTypeMember *> Globals,
1806 ArrayRef<ICallBranchFunnel *> ICallBranchFunnels) {
1807 DenseMap<Metadata *, uint64_t> TypeIdIndices;
1808 for (unsigned I = 0; I != TypeIds.size(); ++I)
1809 TypeIdIndices[TypeIds[I]] = I;
1810
1811 // For each type identifier, build a set of indices that refer to members of
1812 // the type identifier.
1813 std::vector<std::set<uint64_t>> TypeMembers(TypeIds.size());
1814 unsigned GlobalIndex = 0;
1815 DenseMap<GlobalTypeMember *, uint64_t> GlobalIndices;
1816 for (GlobalTypeMember *GTM : Globals) {
1817 for (MDNode *Type : GTM->types()) {
1818 // Type = { offset, type identifier }
1819 auto I = TypeIdIndices.find(Val: Type->getOperand(I: 1));
1820 if (I != TypeIdIndices.end())
1821 TypeMembers[I->second].insert(x: GlobalIndex);
1822 }
1823 GlobalIndices[GTM] = GlobalIndex;
1824 GlobalIndex++;
1825 }
1826
1827 for (ICallBranchFunnel *JT : ICallBranchFunnels) {
1828 TypeMembers.emplace_back();
1829 std::set<uint64_t> &TMSet = TypeMembers.back();
1830 for (GlobalTypeMember *T : JT->targets())
1831 TMSet.insert(x: GlobalIndices[T]);
1832 }
1833
1834 // Order the sets of indices by size. The GlobalLayoutBuilder works best
1835 // when given small index sets first.
1836 llvm::stable_sort(Range&: TypeMembers, C: [](const std::set<uint64_t> &O1,
1837 const std::set<uint64_t> &O2) {
1838 return O1.size() < O2.size();
1839 });
1840
1841 // Create a GlobalLayoutBuilder and provide it with index sets as layout
1842 // fragments. The GlobalLayoutBuilder tries to lay out members of fragments as
1843 // close together as possible.
1844 GlobalLayoutBuilder GLB(Globals.size());
1845 for (auto &&MemSet : TypeMembers)
1846 GLB.addFragment(F: MemSet);
1847
1848 // Build a vector of globals with the computed layout.
1849 bool IsGlobalSet =
1850 Globals.empty() || isa<GlobalVariable>(Val: Globals[0]->getGlobal());
1851 std::vector<GlobalTypeMember *> OrderedGTMs(Globals.size());
1852 auto OGTMI = OrderedGTMs.begin();
1853 for (auto &&F : GLB.Fragments) {
1854 for (auto &&Offset : F) {
1855 if (IsGlobalSet != isa<GlobalVariable>(Val: Globals[Offset]->getGlobal()))
1856 report_fatal_error(reason: "Type identifier may not contain both global "
1857 "variables and functions");
1858 *OGTMI++ = Globals[Offset];
1859 }
1860 }
1861
1862 // Build the bitsets from this disjoint set.
1863 if (IsGlobalSet)
1864 buildBitSetsFromGlobalVariables(TypeIds, Globals: OrderedGTMs);
1865 else
1866 buildBitSetsFromFunctions(TypeIds, Functions: OrderedGTMs);
1867}
1868
1869/// Lower all type tests in this module.
1870LowerTypeTestsModule::LowerTypeTestsModule(
1871 Module &M, ModuleAnalysisManager &AM, ModuleSummaryIndex *ExportSummary,
1872 const ModuleSummaryIndex *ImportSummary, DropTestKind DropTypeTests)
1873 : M(M), ExportSummary(ExportSummary), ImportSummary(ImportSummary),
1874 DropTypeTests(ClDropTypeTests > DropTypeTests ? ClDropTypeTests
1875 : DropTypeTests) {
1876 assert(!(ExportSummary && ImportSummary));
1877 Triple TargetTriple(M.getTargetTriple());
1878 Arch = TargetTriple.getArch();
1879 if (Arch == Triple::arm)
1880 CanUseArmJumpTable = true;
1881 if (Arch == Triple::arm || Arch == Triple::thumb) {
1882 auto &FAM =
1883 AM.getResult<FunctionAnalysisManagerModuleProxy>(IR&: M).getManager();
1884 for (Function &F : M) {
1885 // Skip declarations since we should not query the TTI for them.
1886 if (F.isDeclaration())
1887 continue;
1888 auto &TTI = FAM.getResult<TargetIRAnalysis>(IR&: F);
1889 if (TTI.hasArmWideBranch(Thumb: false))
1890 CanUseArmJumpTable = true;
1891 if (TTI.hasArmWideBranch(Thumb: true))
1892 CanUseThumbBWJumpTable = true;
1893 }
1894 }
1895 OS = TargetTriple.getOS();
1896 ObjectFormat = TargetTriple.getObjectFormat();
1897
1898 // Function annotation describes or applies to function itself, and
1899 // shouldn't be associated with jump table thunk generated for CFI.
1900 GlobalAnnotation = M.getGlobalVariable(Name: "llvm.global.annotations");
1901 if (GlobalAnnotation && GlobalAnnotation->hasInitializer()) {
1902 const ConstantArray *CA =
1903 cast<ConstantArray>(Val: GlobalAnnotation->getInitializer());
1904 FunctionAnnotations.insert_range(R: CA->operands());
1905 }
1906}
1907
1908bool LowerTypeTestsModule::runForTesting(Module &M, ModuleAnalysisManager &AM) {
1909 ModuleSummaryIndex Summary(/*HaveGVs=*/false);
1910
1911 // Handle the command-line summary arguments. This code is for testing
1912 // purposes only, so we handle errors directly.
1913 if (!ClReadSummary.empty()) {
1914 ExitOnError ExitOnErr("-lowertypetests-read-summary: " + ClReadSummary +
1915 ": ");
1916 auto ReadSummaryFile = ExitOnErr(errorOrToExpected(
1917 EO: MemoryBuffer::getFile(Filename: ClReadSummary, /*IsText=*/true)));
1918
1919 yaml::Input In(ReadSummaryFile->getBuffer());
1920 In >> Summary;
1921 ExitOnErr(errorCodeToError(EC: In.error()));
1922 }
1923
1924 bool Changed =
1925 LowerTypeTestsModule(
1926 M, AM,
1927 ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr,
1928 ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr,
1929 /*DropTypeTests=*/DropTestKind::None)
1930 .lower();
1931
1932 if (!ClWriteSummary.empty()) {
1933 ExitOnError ExitOnErr("-lowertypetests-write-summary: " + ClWriteSummary +
1934 ": ");
1935 std::error_code EC;
1936 raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_TextWithCRLF);
1937 ExitOnErr(errorCodeToError(EC));
1938
1939 yaml::Output Out(OS);
1940 Out << Summary;
1941 }
1942
1943 return Changed;
1944}
1945
1946static bool isDirectCall(Use& U) {
1947 auto *Usr = dyn_cast<CallInst>(Val: U.getUser());
1948 if (Usr) {
1949 auto *CB = dyn_cast<CallBase>(Val: Usr);
1950 if (CB && CB->isCallee(U: &U))
1951 return true;
1952 }
1953 return false;
1954}
1955
1956void LowerTypeTestsModule::replaceCfiUses(Function *Old, Value *New,
1957 bool IsJumpTableCanonical) {
1958 SmallSetVector<Constant *, 4> Constants;
1959 for (Use &U : llvm::make_early_inc_range(Range: Old->uses())) {
1960 // Skip no_cfi values, which refer to the function body instead of the jump
1961 // table.
1962 if (isa<NoCFIValue>(Val: U.getUser()))
1963 continue;
1964
1965 // Skip direct calls to externally defined or non-dso_local functions.
1966 if (isDirectCall(U) && (Old->isDSOLocal() || !IsJumpTableCanonical))
1967 continue;
1968
1969 // Skip function annotation.
1970 if (isFunctionAnnotation(V: U.getUser()))
1971 continue;
1972
1973 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
1974 // constant because they are uniqued.
1975 if (auto *C = dyn_cast<Constant>(Val: U.getUser())) {
1976 if (!isa<GlobalValue>(Val: C)) {
1977 // Save unique users to avoid processing operand replacement
1978 // more than once.
1979 Constants.insert(X: C);
1980 continue;
1981 }
1982 }
1983
1984 U.set(New);
1985 }
1986
1987 // Process operand replacement of saved constants.
1988 for (auto *C : Constants)
1989 C->handleOperandChange(Old, New);
1990}
1991
1992void LowerTypeTestsModule::replaceDirectCalls(Value *Old, Value *New) {
1993 Old->replaceUsesWithIf(New, ShouldReplace: isDirectCall);
1994}
1995
1996static void dropTypeTests(Module &M, Function &TypeTestFunc,
1997 bool ShouldDropAll) {
1998 for (Use &U : llvm::make_early_inc_range(Range: TypeTestFunc.uses())) {
1999 auto *CI = cast<CallInst>(Val: U.getUser());
2000 // Find and erase llvm.assume intrinsics for this llvm.type.test call.
2001 for (Use &CIU : llvm::make_early_inc_range(Range: CI->uses()))
2002 if (auto *Assume = dyn_cast<AssumeInst>(Val: CIU.getUser()))
2003 Assume->eraseFromParent();
2004 // If the assume was merged with another assume, we might have a use on a
2005 // phi (which will feed the assume). Simply replace the use on the phi
2006 // with "true" and leave the merged assume.
2007 //
2008 // If ShouldDropAll is set, then we we need to update any remaining uses,
2009 // regardless of the instruction type.
2010 if (!CI->use_empty()) {
2011 assert(ShouldDropAll || all_of(CI->users(), [](User *U) -> bool {
2012 return isa<PHINode>(U);
2013 }));
2014 CI->replaceAllUsesWith(V: ConstantInt::getTrue(Context&: M.getContext()));
2015 }
2016 CI->eraseFromParent();
2017 }
2018}
2019
2020bool LowerTypeTestsModule::lower() {
2021 Function *TypeTestFunc =
2022 Intrinsic::getDeclarationIfExists(M: &M, id: Intrinsic::type_test);
2023
2024 if (DropTypeTests != DropTestKind::None) {
2025 bool ShouldDropAll = DropTypeTests == DropTestKind::All;
2026 if (TypeTestFunc)
2027 dropTypeTests(M, TypeTestFunc&: *TypeTestFunc, ShouldDropAll);
2028 // Normally we'd have already removed all @llvm.public.type.test calls,
2029 // except for in the case where we originally were performing ThinLTO but
2030 // decided not to in the backend.
2031 Function *PublicTypeTestFunc =
2032 Intrinsic::getDeclarationIfExists(M: &M, id: Intrinsic::public_type_test);
2033 if (PublicTypeTestFunc)
2034 dropTypeTests(M, TypeTestFunc&: *PublicTypeTestFunc, ShouldDropAll);
2035 if (TypeTestFunc || PublicTypeTestFunc) {
2036 // We have deleted the type intrinsics, so we no longer have enough
2037 // information to reason about the liveness of virtual function pointers
2038 // in GlobalDCE.
2039 for (GlobalVariable &GV : M.globals())
2040 GV.eraseMetadata(KindID: LLVMContext::MD_vcall_visibility);
2041 return true;
2042 }
2043 return false;
2044 }
2045
2046 // If only some of the modules were split, we cannot correctly perform
2047 // this transformation. We already checked for the presense of type tests
2048 // with partially split modules during the thin link, and would have emitted
2049 // an error if any were found, so here we can simply return.
2050 if ((ExportSummary && ExportSummary->partiallySplitLTOUnits()) ||
2051 (ImportSummary && ImportSummary->partiallySplitLTOUnits()))
2052 return false;
2053
2054 Function *ICallBranchFunnelFunc =
2055 Intrinsic::getDeclarationIfExists(M: &M, id: Intrinsic::icall_branch_funnel);
2056 if ((!TypeTestFunc || TypeTestFunc->use_empty()) &&
2057 (!ICallBranchFunnelFunc || ICallBranchFunnelFunc->use_empty()) &&
2058 !ExportSummary && !ImportSummary)
2059 return false;
2060
2061 if (ImportSummary) {
2062 if (TypeTestFunc)
2063 for (Use &U : llvm::make_early_inc_range(Range: TypeTestFunc->uses()))
2064 importTypeTest(CI: cast<CallInst>(Val: U.getUser()));
2065
2066 if (ICallBranchFunnelFunc && !ICallBranchFunnelFunc->use_empty())
2067 report_fatal_error(
2068 reason: "unexpected call to llvm.icall.branch.funnel during import phase");
2069
2070 SmallVector<Function *, 8> Defs;
2071 SmallVector<Function *, 8> Decls;
2072 for (auto &F : M) {
2073 // CFI functions are either external, or promoted. A local function may
2074 // have the same name, but it's not the one we are looking for.
2075 if (F.hasLocalLinkage())
2076 continue;
2077 if (ImportSummary->cfiFunctionDefs().count(S: F.getName()))
2078 Defs.push_back(Elt: &F);
2079 else if (ImportSummary->cfiFunctionDecls().count(S: F.getName()))
2080 Decls.push_back(Elt: &F);
2081 }
2082
2083 {
2084 ScopedSaveAliaseesAndUsed S(M);
2085 for (auto *F : Defs)
2086 importFunction(F, /*isJumpTableCanonical*/ true);
2087 for (auto *F : Decls)
2088 importFunction(F, /*isJumpTableCanonical*/ false);
2089 }
2090
2091 return true;
2092 }
2093
2094 // Equivalence class set containing type identifiers and the globals that
2095 // reference them. This is used to partition the set of type identifiers in
2096 // the module into disjoint sets.
2097 using GlobalClassesTy = EquivalenceClasses<
2098 PointerUnion<GlobalTypeMember *, Metadata *, ICallBranchFunnel *>>;
2099 GlobalClassesTy GlobalClasses;
2100
2101 // Verify the type metadata and build a few data structures to let us
2102 // efficiently enumerate the type identifiers associated with a global:
2103 // a list of GlobalTypeMembers (a GlobalObject stored alongside a vector
2104 // of associated type metadata) and a mapping from type identifiers to their
2105 // list of GlobalTypeMembers and last observed index in the list of globals.
2106 // The indices will be used later to deterministically order the list of type
2107 // identifiers.
2108 BumpPtrAllocator Alloc;
2109 struct TIInfo {
2110 unsigned UniqueId;
2111 std::vector<GlobalTypeMember *> RefGlobals;
2112 };
2113 DenseMap<Metadata *, TIInfo> TypeIdInfo;
2114 unsigned CurUniqueId = 0;
2115 SmallVector<MDNode *, 2> Types;
2116
2117 // Cross-DSO CFI emits jumptable entries for exported functions as well as
2118 // address taken functions in case they are address taken in other modules.
2119 const bool CrossDsoCfi = M.getModuleFlag(Key: "Cross-DSO CFI") != nullptr;
2120
2121 struct ExportedFunctionInfo {
2122 CfiFunctionLinkage Linkage;
2123 MDNode *FuncMD; // {name, linkage, type[, type...]}
2124 };
2125 MapVector<StringRef, ExportedFunctionInfo> ExportedFunctions;
2126 if (ExportSummary) {
2127 NamedMDNode *CfiFunctionsMD = M.getNamedMetadata(Name: "cfi.functions");
2128 if (CfiFunctionsMD) {
2129 // A set of all functions that are address taken by a live global object.
2130 DenseSet<GlobalValue::GUID> AddressTaken;
2131 for (auto &I : *ExportSummary)
2132 for (auto &GVS : I.second.getSummaryList())
2133 if (GVS->isLive())
2134 for (const auto &Ref : GVS->refs()) {
2135 AddressTaken.insert(V: Ref.getGUID());
2136 for (auto &RefGVS : Ref.getSummaryList())
2137 if (auto Alias = dyn_cast<AliasSummary>(Val: RefGVS.get()))
2138 AddressTaken.insert(V: Alias->getAliaseeGUID());
2139 }
2140 auto IsAddressTaken = [&](GlobalValue::GUID GUID) {
2141 if (AddressTaken.count(V: GUID))
2142 return true;
2143 auto VI = ExportSummary->getValueInfo(GUID);
2144 if (!VI)
2145 return false;
2146 for (auto &I : VI.getSummaryList())
2147 if (auto Alias = dyn_cast<AliasSummary>(Val: I.get()))
2148 if (AddressTaken.count(V: Alias->getAliaseeGUID()))
2149 return true;
2150 return false;
2151 };
2152 for (auto *FuncMD : CfiFunctionsMD->operands()) {
2153 assert(FuncMD->getNumOperands() >= 2);
2154 StringRef FunctionName =
2155 cast<MDString>(Val: FuncMD->getOperand(I: 0))->getString();
2156 CfiFunctionLinkage Linkage = static_cast<CfiFunctionLinkage>(
2157 cast<ConstantAsMetadata>(Val: FuncMD->getOperand(I: 1))
2158 ->getValue()
2159 ->getUniqueInteger()
2160 .getZExtValue());
2161 const GlobalValue::GUID GUID =
2162 GlobalValue::getGUIDAssumingExternalLinkage(
2163 GlobalName: GlobalValue::dropLLVMManglingEscape(Name: FunctionName));
2164 // Do not emit jumptable entries for functions that are not-live and
2165 // have no live references (and are not exported with cross-DSO CFI.)
2166 if (!ExportSummary->isGUIDLive(GUID))
2167 continue;
2168 if (!IsAddressTaken(GUID)) {
2169 if (!CrossDsoCfi || Linkage != CFL_Definition)
2170 continue;
2171
2172 bool Exported = false;
2173 if (auto VI = ExportSummary->getValueInfo(GUID))
2174 for (const auto &GVS : VI.getSummaryList())
2175 if (GVS->isLive() && !GlobalValue::isLocalLinkage(Linkage: GVS->linkage()))
2176 Exported = true;
2177
2178 if (!Exported)
2179 continue;
2180 }
2181 auto P = ExportedFunctions.insert(KV: {FunctionName, {.Linkage: Linkage, .FuncMD: FuncMD}});
2182 if (!P.second && P.first->second.Linkage != CFL_Definition)
2183 P.first->second = {.Linkage: Linkage, .FuncMD: FuncMD};
2184 }
2185
2186 for (const auto &P : ExportedFunctions) {
2187 StringRef FunctionName = P.first;
2188 CfiFunctionLinkage Linkage = P.second.Linkage;
2189 MDNode *FuncMD = P.second.FuncMD;
2190 Function *F = M.getFunction(Name: FunctionName);
2191 if (F && F->hasLocalLinkage()) {
2192 // Locally defined function that happens to have the same name as a
2193 // function defined in a ThinLTO module. Rename it to move it out of
2194 // the way of the external reference that we're about to create.
2195 // Note that setName will find a unique name for the function, so even
2196 // if there is an existing function with the suffix there won't be a
2197 // name collision.
2198 F->setName(F->getName() + ".1");
2199 F = nullptr;
2200 }
2201
2202 if (!F)
2203 F = Function::Create(
2204 Ty: FunctionType::get(Result: Type::getVoidTy(C&: M.getContext()), isVarArg: false),
2205 Linkage: GlobalVariable::ExternalLinkage,
2206 AddrSpace: M.getDataLayout().getProgramAddressSpace(), N: FunctionName, M: &M);
2207
2208 // If the function is available_externally, remove its definition so
2209 // that it is handled the same way as a declaration. Later we will try
2210 // to create an alias using this function's linkage, which will fail if
2211 // the linkage is available_externally. This will also result in us
2212 // following the code path below to replace the type metadata.
2213 if (F->hasAvailableExternallyLinkage()) {
2214 F->setLinkage(GlobalValue::ExternalLinkage);
2215 F->deleteBody();
2216 F->setComdat(nullptr);
2217 F->clearMetadata();
2218 }
2219
2220 // Update the linkage for extern_weak declarations when a definition
2221 // exists.
2222 if (Linkage == CFL_Definition && F->hasExternalWeakLinkage())
2223 F->setLinkage(GlobalValue::ExternalLinkage);
2224
2225 // If the function in the full LTO module is a declaration, replace its
2226 // type metadata with the type metadata we found in cfi.functions. That
2227 // metadata is presumed to be more accurate than the metadata attached
2228 // to the declaration.
2229 if (F->isDeclaration()) {
2230 if (Linkage == CFL_WeakDeclaration)
2231 F->setLinkage(GlobalValue::ExternalWeakLinkage);
2232
2233 F->eraseMetadata(KindID: LLVMContext::MD_type);
2234 for (unsigned I = 2; I < FuncMD->getNumOperands(); ++I)
2235 F->addMetadata(KindID: LLVMContext::MD_type,
2236 MD&: *cast<MDNode>(Val: FuncMD->getOperand(I).get()));
2237 }
2238 }
2239 }
2240 }
2241
2242 struct AliasToCreate {
2243 Function *Alias;
2244 std::string TargetName;
2245 };
2246 std::vector<AliasToCreate> AliasesToCreate;
2247
2248 // Parse alias data to replace stand-in function declarations for aliases
2249 // with an alias to the intended target.
2250 if (ExportSummary) {
2251 if (NamedMDNode *AliasesMD = M.getNamedMetadata(Name: "aliases")) {
2252 for (auto *AliasMD : AliasesMD->operands()) {
2253 SmallVector<Function *> Aliases;
2254 for (Metadata *MD : AliasMD->operands()) {
2255 auto *MDS = dyn_cast<MDString>(Val: MD);
2256 if (!MDS)
2257 continue;
2258 StringRef AliasName = MDS->getString();
2259 if (!ExportedFunctions.count(Key: AliasName))
2260 continue;
2261 auto *AliasF = M.getFunction(Name: AliasName);
2262 if (AliasF)
2263 Aliases.push_back(Elt: AliasF);
2264 }
2265
2266 if (Aliases.empty())
2267 continue;
2268
2269 for (unsigned I = 1; I != Aliases.size(); ++I) {
2270 auto *AliasF = Aliases[I];
2271 ExportedFunctions.erase(Key: AliasF->getName());
2272 AliasesToCreate.push_back(
2273 x: {.Alias: AliasF, .TargetName: std::string(Aliases[0]->getName())});
2274 }
2275 }
2276 }
2277 }
2278
2279 DenseMap<GlobalObject *, GlobalTypeMember *> GlobalTypeMembers;
2280 for (GlobalObject &GO : M.global_objects()) {
2281 if (isa<GlobalVariable>(Val: GO) && GO.isDeclarationForLinker())
2282 continue;
2283
2284 Types.clear();
2285 GO.getMetadata(KindID: LLVMContext::MD_type, MDs&: Types);
2286
2287 bool IsJumpTableCanonical = false;
2288 bool IsExported = false;
2289 if (Function *F = dyn_cast<Function>(Val: &GO)) {
2290 IsJumpTableCanonical = isJumpTableCanonical(F);
2291 if (auto It = ExportedFunctions.find(Key: F->getName());
2292 It != ExportedFunctions.end()) {
2293 IsJumpTableCanonical |= It->second.Linkage == CFL_Definition;
2294 IsExported = true;
2295 // TODO: The logic here checks only that the function is address taken,
2296 // not that the address takers are live. This can be updated to check
2297 // their liveness and emit fewer jumptable entries once monolithic LTO
2298 // builds also emit summaries.
2299 } else if (!F->hasAddressTaken()) {
2300 if (!CrossDsoCfi || !IsJumpTableCanonical || F->hasLocalLinkage())
2301 continue;
2302 }
2303 }
2304
2305 auto *GTM = GlobalTypeMember::create(Alloc, GO: &GO, IsJumpTableCanonical,
2306 IsExported, Types);
2307 GlobalTypeMembers[&GO] = GTM;
2308 for (MDNode *Type : Types) {
2309 verifyTypeMDNode(GO: &GO, Type);
2310 auto &Info = TypeIdInfo[Type->getOperand(I: 1)];
2311 Info.UniqueId = ++CurUniqueId;
2312 Info.RefGlobals.push_back(x: GTM);
2313 }
2314 }
2315
2316 auto AddTypeIdUse = [&](Metadata *TypeId) -> TypeIdUserInfo & {
2317 // Add the call site to the list of call sites for this type identifier. We
2318 // also use TypeIdUsers to keep track of whether we have seen this type
2319 // identifier before. If we have, we don't need to re-add the referenced
2320 // globals to the equivalence class.
2321 auto Ins = TypeIdUsers.insert(KV: {TypeId, {}});
2322 if (Ins.second) {
2323 // Add the type identifier to the equivalence class.
2324 auto &GCI = GlobalClasses.insert(Data: TypeId);
2325 GlobalClassesTy::member_iterator CurSet = GlobalClasses.findLeader(ECV: GCI);
2326
2327 // Add the referenced globals to the type identifier's equivalence class.
2328 for (GlobalTypeMember *GTM : TypeIdInfo[TypeId].RefGlobals)
2329 CurSet = GlobalClasses.unionSets(
2330 L1: CurSet, L2: GlobalClasses.findLeader(ECV: GlobalClasses.insert(Data: GTM)));
2331 }
2332
2333 return Ins.first->second;
2334 };
2335
2336 if (TypeTestFunc) {
2337 for (const Use &U : TypeTestFunc->uses()) {
2338 auto CI = cast<CallInst>(Val: U.getUser());
2339 // If this type test is only used by llvm.assume instructions, it
2340 // was used for whole program devirtualization, and is being kept
2341 // for use by other optimization passes. We do not need or want to
2342 // lower it here. We also don't want to rewrite any associated globals
2343 // unnecessarily. These will be removed by a subsequent LTT invocation
2344 // with the DropTypeTests flag set.
2345 bool OnlyAssumeUses = !CI->use_empty();
2346 for (const Use &CIU : CI->uses()) {
2347 if (isa<AssumeInst>(Val: CIU.getUser()))
2348 continue;
2349 OnlyAssumeUses = false;
2350 break;
2351 }
2352 if (OnlyAssumeUses)
2353 continue;
2354
2355 auto TypeIdMDVal = dyn_cast<MetadataAsValue>(Val: CI->getArgOperand(i: 1));
2356 if (!TypeIdMDVal)
2357 report_fatal_error(reason: "Second argument of llvm.type.test must be metadata");
2358 auto TypeId = TypeIdMDVal->getMetadata();
2359 AddTypeIdUse(TypeId).CallSites.push_back(x: CI);
2360 }
2361 }
2362
2363 if (ICallBranchFunnelFunc) {
2364 for (const Use &U : ICallBranchFunnelFunc->uses()) {
2365 if (Arch != Triple::x86_64)
2366 report_fatal_error(
2367 reason: "llvm.icall.branch.funnel not supported on this target");
2368
2369 auto CI = cast<CallInst>(Val: U.getUser());
2370
2371 std::vector<GlobalTypeMember *> Targets;
2372 if (CI->arg_size() % 2 != 1)
2373 report_fatal_error(reason: "number of arguments should be odd");
2374
2375 GlobalClassesTy::member_iterator CurSet;
2376 for (unsigned I = 1; I != CI->arg_size(); I += 2) {
2377 int64_t Offset;
2378 auto *Base = dyn_cast<GlobalObject>(Val: GetPointerBaseWithConstantOffset(
2379 Ptr: CI->getOperand(i_nocapture: I), Offset, DL: M.getDataLayout()));
2380 if (!Base)
2381 report_fatal_error(
2382 reason: "Expected branch funnel operand to be global value");
2383
2384 GlobalTypeMember *GTM = GlobalTypeMembers[Base];
2385 Targets.push_back(x: GTM);
2386 GlobalClassesTy::member_iterator NewSet =
2387 GlobalClasses.findLeader(ECV: GlobalClasses.insert(Data: GTM));
2388 if (I == 1)
2389 CurSet = NewSet;
2390 else
2391 CurSet = GlobalClasses.unionSets(L1: CurSet, L2: NewSet);
2392 }
2393
2394 GlobalClasses.unionSets(
2395 L1: CurSet, L2: GlobalClasses.findLeader(
2396 ECV: GlobalClasses.insert(Data: ICallBranchFunnel::create(
2397 Alloc, CI, Targets, UniqueId: ++CurUniqueId))));
2398 }
2399 }
2400
2401 if (ExportSummary) {
2402 DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID;
2403 for (auto &P : TypeIdInfo) {
2404 if (auto *TypeId = dyn_cast<MDString>(Val: P.first))
2405 MetadataByGUID[GlobalValue::getGUIDAssumingExternalLinkage(
2406 GlobalName: TypeId->getString())]
2407 .push_back(NewVal: TypeId);
2408 }
2409
2410 for (auto &P : *ExportSummary) {
2411 for (auto &S : P.second.getSummaryList()) {
2412 if (!ExportSummary->isGlobalValueLive(GVS: S.get()))
2413 continue;
2414 if (auto *FS = dyn_cast<FunctionSummary>(Val: S->getBaseObject()))
2415 for (GlobalValue::GUID G : FS->type_tests())
2416 for (Metadata *MD : MetadataByGUID[G])
2417 AddTypeIdUse(MD).IsExported = true;
2418 }
2419 }
2420 }
2421
2422 if (GlobalClasses.empty())
2423 return false;
2424
2425 {
2426 ScopedSaveAliaseesAndUsed S(M);
2427 // For each disjoint set we found...
2428 for (const auto &C : GlobalClasses) {
2429 if (!C->isLeader())
2430 continue;
2431
2432 ++NumTypeIdDisjointSets;
2433 // Build the list of type identifiers in this disjoint set.
2434 std::vector<Metadata *> TypeIds;
2435 std::vector<GlobalTypeMember *> Globals;
2436 std::vector<ICallBranchFunnel *> ICallBranchFunnels;
2437 for (auto M : GlobalClasses.members(ECV: *C)) {
2438 if (isa<Metadata *>(Val: M))
2439 TypeIds.push_back(x: cast<Metadata *>(Val&: M));
2440 else if (isa<GlobalTypeMember *>(Val: M))
2441 Globals.push_back(x: cast<GlobalTypeMember *>(Val&: M));
2442 else
2443 ICallBranchFunnels.push_back(x: cast<ICallBranchFunnel *>(Val&: M));
2444 }
2445
2446 // Order type identifiers by unique ID for determinism. This ordering is
2447 // stable as there is a one-to-one mapping between metadata and unique
2448 // IDs.
2449 llvm::sort(C&: TypeIds, Comp: [&](Metadata *M1, Metadata *M2) {
2450 return TypeIdInfo[M1].UniqueId < TypeIdInfo[M2].UniqueId;
2451 });
2452
2453 // Same for the branch funnels.
2454 llvm::sort(C&: ICallBranchFunnels,
2455 Comp: [&](ICallBranchFunnel *F1, ICallBranchFunnel *F2) {
2456 return F1->UniqueId < F2->UniqueId;
2457 });
2458
2459 // Build bitsets for this disjoint set.
2460 buildBitSetsFromDisjointSet(TypeIds, Globals, ICallBranchFunnels);
2461 }
2462 }
2463
2464 allocateByteArrays();
2465
2466 for (auto A : AliasesToCreate) {
2467 auto *Target = M.getNamedValue(Name: A.TargetName);
2468 if (!isa<GlobalAlias>(Val: Target))
2469 continue;
2470 auto *AliasGA = GlobalAlias::create(Name: "", Aliasee: Target);
2471 AliasGA->setVisibility(A.Alias->getVisibility());
2472 AliasGA->setLinkage(A.Alias->getLinkage());
2473 AliasGA->takeName(V: A.Alias);
2474 A.Alias->replaceAllUsesWith(V: AliasGA);
2475 A.Alias->eraseFromParent();
2476 }
2477
2478 // Emit .symver directives for exported functions, if they exist.
2479 if (ExportSummary) {
2480 if (NamedMDNode *SymversMD = M.getNamedMetadata(Name: "symvers")) {
2481 for (auto *Symver : SymversMD->operands()) {
2482 assert(Symver->getNumOperands() >= 2);
2483 StringRef SymbolName =
2484 cast<MDString>(Val: Symver->getOperand(I: 0))->getString();
2485 StringRef Alias = cast<MDString>(Val: Symver->getOperand(I: 1))->getString();
2486
2487 if (!ExportedFunctions.count(Key: SymbolName))
2488 continue;
2489
2490 M.appendModuleInlineAsm(
2491 Asm: (llvm::Twine(".symver ") + SymbolName + ", " + Alias).str());
2492 }
2493 }
2494 }
2495
2496 return true;
2497}
2498
2499PreservedAnalyses LowerTypeTestsPass::run(Module &M,
2500 ModuleAnalysisManager &AM) {
2501 bool Changed;
2502 if (UseCommandLine)
2503 Changed = LowerTypeTestsModule::runForTesting(M, AM);
2504 else
2505 Changed =
2506 LowerTypeTestsModule(M, AM, ExportSummary, ImportSummary, DropTypeTests)
2507 .lower();
2508 if (!Changed)
2509 return PreservedAnalyses::all();
2510 return PreservedAnalyses::none();
2511}
2512
2513PreservedAnalyses SimplifyTypeTestsPass::run(Module &M,
2514 ModuleAnalysisManager &AM) {
2515 bool Changed = false;
2516 // Figure out whether inlining has exposed a constant address to a lowered
2517 // type test, and remove the test if so and the address is known to pass the
2518 // test. Unfortunately this pass ends up needing to reverse engineer what
2519 // LowerTypeTests did; this is currently inherent to the design of ThinLTO
2520 // importing where LowerTypeTests needs to run at the start.
2521 //
2522 // We look for things like:
2523 //
2524 // sub (i64 ptrtoint (ptr @_Z2fpv to i64), i64 ptrtoint (ptr
2525 // @__typeid__ZTSFvvE_global_addr to i64))
2526 //
2527 // which gets replaced with 0 if _Z2fpv (more specifically _Z2fpv.cfi, the
2528 // function referred to by the jump table) is a member of the type _ZTSFvv, as
2529 // well as things like
2530 //
2531 // icmp eq ptr @_Z2fpv, @__typeid__ZTSFvvE_global_addr
2532 //
2533 // which gets replaced with true if _Z2fpv is a member.
2534 for (auto &GV : M.globals()) {
2535 if (!GV.getName().starts_with(Prefix: "__typeid_") ||
2536 !GV.getName().ends_with(Suffix: "_global_addr"))
2537 continue;
2538 // __typeid_foo_global_addr -> foo
2539 auto *MD = MDString::get(Context&: M.getContext(),
2540 Str: GV.getName().substr(Start: 9, N: GV.getName().size() - 21));
2541 auto MaySimplifyPtr = [&](Value *Ptr) {
2542 if (auto *GV = dyn_cast<GlobalValue>(Val: Ptr))
2543 if (auto *CFIGV = M.getNamedValue(Name: (GV->getName() + ".cfi").str()))
2544 Ptr = CFIGV;
2545 return isKnownTypeIdMember(TypeId: MD, DL: M.getDataLayout(), V: Ptr, COffset: 0);
2546 };
2547 auto MaySimplifyInt = [&](Value *Op) {
2548 auto *PtrAsInt = dyn_cast<ConstantExpr>(Val: Op);
2549 if (!PtrAsInt || PtrAsInt->getOpcode() != Instruction::PtrToInt)
2550 return false;
2551 return MaySimplifyPtr(PtrAsInt->getOperand(i_nocapture: 0));
2552 };
2553 for (User *U : make_early_inc_range(Range: GV.users())) {
2554 if (auto *CI = dyn_cast<ICmpInst>(Val: U)) {
2555 if (CI->getPredicate() == CmpInst::ICMP_EQ &&
2556 MaySimplifyPtr(CI->getOperand(i_nocapture: 0))) {
2557 // This is an equality comparison (TypeTestResolution::Single case in
2558 // lowerTypeTestCall). In this case we just replace the comparison
2559 // with true.
2560 CI->replaceAllUsesWith(V: ConstantInt::getTrue(Context&: M.getContext()));
2561 CI->eraseFromParent();
2562 Changed = true;
2563 continue;
2564 }
2565 }
2566 auto *CE = dyn_cast<ConstantExpr>(Val: U);
2567 if (!CE || CE->getOpcode() != Instruction::PtrToInt)
2568 continue;
2569 for (Use &U : make_early_inc_range(Range: CE->uses())) {
2570 auto *CE = dyn_cast<ConstantExpr>(Val: U.getUser());
2571 if (U.getOperandNo() == 0 && CE &&
2572 CE->getOpcode() == Instruction::Sub &&
2573 MaySimplifyInt(CE->getOperand(i_nocapture: 1))) {
2574 // This is a computation of PtrOffset as generated by
2575 // LowerTypeTestsModule::lowerTypeTestCall above. If
2576 // isKnownTypeIdMember passes we just pretend it evaluated to 0. This
2577 // should cause later passes to remove the range and alignment checks.
2578 // The bitset checks won't be removed but those are uncommon.
2579 CE->replaceAllUsesWith(V: ConstantInt::get(Ty: CE->getType(), V: 0));
2580 Changed = true;
2581 }
2582 auto *CI = dyn_cast<ICmpInst>(Val: U.getUser());
2583 if (U.getOperandNo() == 1 && CI &&
2584 CI->getPredicate() == CmpInst::ICMP_EQ &&
2585 MaySimplifyInt(CI->getOperand(i_nocapture: 0))) {
2586 // This is an equality comparison. Unlike in the case above it
2587 // remained as an integer compare.
2588 CI->replaceAllUsesWith(V: ConstantInt::getTrue(Context&: M.getContext()));
2589 CI->eraseFromParent();
2590 Changed = true;
2591 }
2592 }
2593 }
2594 }
2595
2596 if (!Changed)
2597 return PreservedAnalyses::all();
2598 PreservedAnalyses PA = PreservedAnalyses::none();
2599 PA.preserve<DominatorTreeAnalysis>();
2600 PA.preserve<PostDominatorTreeAnalysis>();
2601 PA.preserve<LoopAnalysis>();
2602 return PA;
2603}
2604