1//===-- SPIRVStructurizer.cpp ----------------------*- C++ -*-===//
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//===----------------------------------------------------------------------===//
10
11#include "Analysis/SPIRVConvergenceRegionAnalysis.h"
12#include "SPIRV.h"
13#include "SPIRVStructurizerWrapper.h"
14#include "SPIRVSubtarget.h"
15#include "SPIRVUtils.h"
16#include "llvm/ADT/DenseMap.h"
17#include "llvm/ADT/SmallPtrSet.h"
18#include "llvm/Analysis/LoopInfo.h"
19#include "llvm/CodeGen/IntrinsicLowering.h"
20#include "llvm/IR/CFG.h"
21#include "llvm/IR/Dominators.h"
22#include "llvm/IR/IRBuilder.h"
23#include "llvm/IR/IntrinsicInst.h"
24#include "llvm/IR/Intrinsics.h"
25#include "llvm/IR/IntrinsicsSPIRV.h"
26#include "llvm/IR/LegacyPassManager.h"
27#include "llvm/InitializePasses.h"
28#include "llvm/Transforms/Utils.h"
29#include "llvm/Transforms/Utils/Cloning.h"
30#include "llvm/Transforms/Utils/LoopSimplify.h"
31#include "llvm/Transforms/Utils/LowerMemIntrinsics.h"
32#include <stack>
33#include <unordered_set>
34
35using namespace llvm;
36using namespace SPIRV;
37
38using BlockSet = std::unordered_set<BasicBlock *>;
39using Edge = std::pair<BasicBlock *, BasicBlock *>;
40
41// Helper function to do a partial order visit from the block |Start|, calling
42// |Op| on each visited node.
43static void partialOrderVisit(BasicBlock &Start,
44 std::function<bool(BasicBlock *)> Op) {
45 PartialOrderingVisitor V(*Start.getParent());
46 V.partialOrderVisit(Start, Op);
47}
48
49// Returns the exact convergence region in the tree defined by `Node` for which
50// `BB` is the header, nullptr otherwise.
51static const ConvergenceRegion *
52getRegionForHeader(const ConvergenceRegion *Node, BasicBlock *BB) {
53 if (Node->Entry == BB)
54 return Node;
55
56 for (auto *Child : Node->Children) {
57 const auto *CR = getRegionForHeader(Node: Child, BB);
58 if (CR != nullptr)
59 return CR;
60 }
61 return nullptr;
62}
63
64// Returns the single BasicBlock exiting the convergence region `CR`,
65// nullptr if no such exit exists.
66static BasicBlock *getExitFor(const ConvergenceRegion *CR) {
67 std::unordered_set<BasicBlock *> ExitTargets;
68 for (BasicBlock *Exit : CR->Exits) {
69 for (BasicBlock *Successor : successors(BB: Exit)) {
70 if (CR->Blocks.count(Ptr: Successor) == 0)
71 ExitTargets.insert(x: Successor);
72 }
73 }
74
75 assert(ExitTargets.size() <= 1);
76 if (ExitTargets.size() == 0)
77 return nullptr;
78
79 return *ExitTargets.begin();
80}
81
82// Returns the merge block designated by I if I is a merge instruction, nullptr
83// otherwise.
84static BasicBlock *getDesignatedMergeBlock(Instruction *I) {
85 IntrinsicInst *II = dyn_cast_or_null<IntrinsicInst>(Val: I);
86 if (II == nullptr)
87 return nullptr;
88
89 if (II->getIntrinsicID() != Intrinsic::spv_loop_merge &&
90 II->getIntrinsicID() != Intrinsic::spv_selection_merge)
91 return nullptr;
92
93 BlockAddress *BA = cast<BlockAddress>(Val: II->getOperand(i_nocapture: 0));
94 return BA->getBasicBlock();
95}
96
97// Returns the continue block designated by I if I is an OpLoopMerge, nullptr
98// otherwise.
99static BasicBlock *getDesignatedContinueBlock(Instruction *I) {
100 IntrinsicInst *II = dyn_cast_or_null<IntrinsicInst>(Val: I);
101 if (II == nullptr)
102 return nullptr;
103
104 if (II->getIntrinsicID() != Intrinsic::spv_loop_merge)
105 return nullptr;
106
107 BlockAddress *BA = cast<BlockAddress>(Val: II->getOperand(i_nocapture: 1));
108 return BA->getBasicBlock();
109}
110
111// Returns true if Header has one merge instruction which designated Merge as
112// merge block.
113static bool isDefinedAsSelectionMergeBy(BasicBlock &Header, BasicBlock &Merge) {
114 for (auto &I : Header) {
115 BasicBlock *MB = getDesignatedMergeBlock(I: &I);
116 if (MB == &Merge)
117 return true;
118 }
119 return false;
120}
121
122// Returns true if the BB has one OpLoopMerge instruction.
123static bool hasLoopMergeInstruction(BasicBlock &BB) {
124 for (auto &I : BB)
125 if (getDesignatedContinueBlock(I: &I))
126 return true;
127 return false;
128}
129
130// Returns true is I is an OpSelectionMerge or OpLoopMerge instruction, false
131// otherwise.
132static bool isMergeInstruction(Instruction *I) {
133 return getDesignatedMergeBlock(I) != nullptr;
134}
135
136// Returns all blocks in F having at least one OpLoopMerge or OpSelectionMerge
137// instruction.
138static SmallPtrSet<BasicBlock *, 2> getHeaderBlocks(Function &F) {
139 SmallPtrSet<BasicBlock *, 2> Output;
140 for (BasicBlock &BB : F) {
141 for (Instruction &I : BB) {
142 if (getDesignatedMergeBlock(I: &I) != nullptr)
143 Output.insert(Ptr: &BB);
144 }
145 }
146 return Output;
147}
148
149// Returns all basic blocks in |F| referenced by at least 1
150// OpSelectionMerge/OpLoopMerge instruction.
151static SmallPtrSet<BasicBlock *, 2> getMergeBlocks(Function &F) {
152 SmallPtrSet<BasicBlock *, 2> Output;
153 for (BasicBlock &BB : F) {
154 for (Instruction &I : BB) {
155 BasicBlock *MB = getDesignatedMergeBlock(I: &I);
156 if (MB != nullptr)
157 Output.insert(Ptr: MB);
158 }
159 }
160 return Output;
161}
162
163// Return all the merge instructions contained in BB.
164// Note: the SPIR-V spec doesn't allow a single BB to contain more than 1 merge
165// instruction, but this can happen while we structurize the CFG.
166static std::vector<Instruction *> getMergeInstructions(BasicBlock &BB) {
167 std::vector<Instruction *> Output;
168 for (Instruction &I : BB)
169 if (isMergeInstruction(I: &I))
170 Output.push_back(x: &I);
171 return Output;
172}
173
174// Returns all basic blocks in |F| referenced as continue target by at least 1
175// OpLoopMerge instruction.
176static SmallPtrSet<BasicBlock *, 2> getContinueBlocks(Function &F) {
177 SmallPtrSet<BasicBlock *, 2> Output;
178 for (BasicBlock &BB : F) {
179 for (Instruction &I : BB) {
180 BasicBlock *MB = getDesignatedContinueBlock(I: &I);
181 if (MB != nullptr)
182 Output.insert(Ptr: MB);
183 }
184 }
185 return Output;
186}
187
188// Do a preorder traversal of the CFG starting from the BB |Start|.
189// point. Calls |op| on each basic block encountered during the traversal.
190static void visit(BasicBlock &Start, std::function<bool(BasicBlock *)> op) {
191 std::stack<BasicBlock *> ToVisit;
192 SmallPtrSet<BasicBlock *, 8> Seen;
193
194 ToVisit.push(x: &Start);
195 Seen.insert(Ptr: ToVisit.top());
196 while (ToVisit.size() != 0) {
197 BasicBlock *BB = ToVisit.top();
198 ToVisit.pop();
199
200 if (!op(BB))
201 continue;
202
203 for (auto Succ : successors(BB)) {
204 if (Seen.contains(Ptr: Succ))
205 continue;
206 ToVisit.push(x: Succ);
207 Seen.insert(Ptr: Succ);
208 }
209 }
210}
211
212// Replaces the conditional and unconditional branch targets of |BB| by
213// |NewTarget| if the target was |OldTarget|. This function also makes sure the
214// associated merge instruction gets updated accordingly.
215static void replaceIfBranchTargets(BasicBlock *BB, BasicBlock *OldTarget,
216 BasicBlock *NewTarget) {
217 auto *BI = cast<BranchInst>(Val: BB->getTerminator());
218
219 // 1. Replace all matching successors.
220 for (size_t i = 0; i < BI->getNumSuccessors(); i++) {
221 if (BI->getSuccessor(i) == OldTarget)
222 BI->setSuccessor(idx: i, NewSucc: NewTarget);
223 }
224
225 // Branch was unconditional, no fixup required.
226 if (BI->isUnconditional())
227 return;
228
229 // Branch had 2 successors, maybe now both are the same?
230 if (BI->getSuccessor(i: 0) != BI->getSuccessor(i: 1))
231 return;
232
233 // Note: we may end up here because the original IR had such branches.
234 // This means Target is not necessarily equal to NewTarget.
235 IRBuilder<> Builder(BB);
236 Builder.SetInsertPoint(BI);
237 Builder.CreateBr(Dest: BI->getSuccessor(i: 0));
238 BI->eraseFromParent();
239
240 // The branch was the only instruction, nothing else to do.
241 if (BB->size() == 1)
242 return;
243
244 // Otherwise, we need to check: was there an OpSelectionMerge before this
245 // branch? If we removed the OpBranchConditional, we must also remove the
246 // OpSelectionMerge. This is not valid for OpLoopMerge:
247 IntrinsicInst *II =
248 dyn_cast<IntrinsicInst>(Val: BB->getTerminator()->getPrevNode());
249 if (!II || II->getIntrinsicID() != Intrinsic::spv_selection_merge)
250 return;
251
252 Constant *C = cast<Constant>(Val: II->getOperand(i_nocapture: 0));
253 II->eraseFromParent();
254 if (!C->isConstantUsed())
255 C->destroyConstant();
256}
257
258// Replaces the target of branch instruction in |BB| with |NewTarget| if it
259// was |OldTarget|. This function also fixes the associated merge instruction.
260// Note: this function does not simplify branching instructions, it only updates
261// targets. See also: simplifyBranches.
262static void replaceBranchTargets(BasicBlock *BB, BasicBlock *OldTarget,
263 BasicBlock *NewTarget) {
264 auto *T = BB->getTerminator();
265 if (isa<ReturnInst>(Val: T))
266 return;
267
268 if (isa<BranchInst>(Val: T))
269 return replaceIfBranchTargets(BB, OldTarget, NewTarget);
270
271 if (auto *SI = dyn_cast<SwitchInst>(Val: T)) {
272 for (size_t i = 0; i < SI->getNumSuccessors(); i++) {
273 if (SI->getSuccessor(idx: i) == OldTarget)
274 SI->setSuccessor(idx: i, NewSucc: NewTarget);
275 }
276 return;
277 }
278
279 assert(false && "Unhandled terminator type.");
280}
281
282namespace {
283// Given a reducible CFG, produces a structurized CFG in the SPIR-V sense,
284// adding merge instructions when required.
285class SPIRVStructurizer : public FunctionPass {
286 struct DivergentConstruct;
287 // Represents a list of condition/loops/switch constructs.
288 // See SPIR-V 2.11.2. Structured Control-flow Constructs for the list of
289 // constructs.
290 using ConstructList = std::vector<std::unique_ptr<DivergentConstruct>>;
291
292 // Represents a divergent construct in the SPIR-V sense.
293 // Such constructs are represented by a header (entry), a merge block (exit),
294 // and possibly a continue block (back-edge). A construct can contain other
295 // constructs, but their boundaries do not cross.
296 struct DivergentConstruct {
297 BasicBlock *Header = nullptr;
298 BasicBlock *Merge = nullptr;
299 BasicBlock *Continue = nullptr;
300
301 DivergentConstruct *Parent = nullptr;
302 ConstructList Children;
303 };
304
305 // An helper class to clean the construct boundaries.
306 // It is used to gather the list of blocks that should belong to each
307 // divergent construct, and possibly modify CFG edges when exits would cross
308 // the boundary of multiple constructs.
309 struct Splitter {
310 Function &F;
311 LoopInfo &LI;
312 DomTreeBuilder::BBDomTree DT;
313 DomTreeBuilder::BBPostDomTree PDT;
314
315 Splitter(Function &F, LoopInfo &LI) : F(F), LI(LI) { invalidate(); }
316
317 void invalidate() {
318 PDT.recalculate(Func&: F);
319 DT.recalculate(Func&: F);
320 }
321
322 // Returns the list of blocks that belong to a SPIR-V loop construct,
323 // including the continue construct.
324 std::vector<BasicBlock *> getLoopConstructBlocks(BasicBlock *Header,
325 BasicBlock *Merge) {
326 assert(DT.dominates(Header, Merge));
327 std::vector<BasicBlock *> Output;
328 partialOrderVisit(Start&: *Header, Op: [&](BasicBlock *BB) {
329 if (BB == Merge)
330 return false;
331 if (DT.dominates(A: Merge, B: BB) || !DT.dominates(A: Header, B: BB))
332 return false;
333 Output.push_back(x: BB);
334 return true;
335 });
336 return Output;
337 }
338
339 // Returns the list of blocks that belong to a SPIR-V selection construct.
340 std::vector<BasicBlock *>
341 getSelectionConstructBlocks(DivergentConstruct *Node) {
342 assert(DT.dominates(Node->Header, Node->Merge));
343 BlockSet OutsideBlocks;
344 OutsideBlocks.insert(x: Node->Merge);
345
346 for (DivergentConstruct *It = Node->Parent; It != nullptr;
347 It = It->Parent) {
348 OutsideBlocks.insert(x: It->Merge);
349 if (It->Continue)
350 OutsideBlocks.insert(x: It->Continue);
351 }
352
353 std::vector<BasicBlock *> Output;
354 partialOrderVisit(Start&: *Node->Header, Op: [&](BasicBlock *BB) {
355 if (OutsideBlocks.count(x: BB) != 0)
356 return false;
357 if (DT.dominates(A: Node->Merge, B: BB) || !DT.dominates(A: Node->Header, B: BB))
358 return false;
359 Output.push_back(x: BB);
360 return true;
361 });
362 return Output;
363 }
364
365 // Returns the list of blocks that belong to a SPIR-V switch construct.
366 std::vector<BasicBlock *> getSwitchConstructBlocks(BasicBlock *Header,
367 BasicBlock *Merge) {
368 assert(DT.dominates(Header, Merge));
369
370 std::vector<BasicBlock *> Output;
371 partialOrderVisit(Start&: *Header, Op: [&](BasicBlock *BB) {
372 // the blocks structurally dominated by a switch header,
373 if (!DT.dominates(A: Header, B: BB))
374 return false;
375 // excluding blocks structurally dominated by the switch header’s merge
376 // block.
377 if (DT.dominates(A: Merge, B: BB) || BB == Merge)
378 return false;
379 Output.push_back(x: BB);
380 return true;
381 });
382 return Output;
383 }
384
385 // Returns the list of blocks that belong to a SPIR-V case construct.
386 std::vector<BasicBlock *> getCaseConstructBlocks(BasicBlock *Target,
387 BasicBlock *Merge) {
388 assert(DT.dominates(Target, Merge));
389
390 std::vector<BasicBlock *> Output;
391 partialOrderVisit(Start&: *Target, Op: [&](BasicBlock *BB) {
392 // the blocks structurally dominated by an OpSwitch Target or Default
393 // block
394 if (!DT.dominates(A: Target, B: BB))
395 return false;
396 // excluding the blocks structurally dominated by the OpSwitch
397 // construct’s corresponding merge block.
398 if (DT.dominates(A: Merge, B: BB) || BB == Merge)
399 return false;
400 Output.push_back(x: BB);
401 return true;
402 });
403 return Output;
404 }
405
406 // Splits the given edges by recreating proxy nodes so that the destination
407 // has unique incoming edges from this region.
408 //
409 // clang-format off
410 //
411 // In SPIR-V, constructs must have a single exit/merge.
412 // Given nodes A and B in the construct, a node C outside, and the following edges.
413 // A -> C
414 // B -> C
415 //
416 // In such cases, we must create a new exit node D, that belong to the construct to make is viable:
417 // A -> D -> C
418 // B -> D -> C
419 //
420 // This is fine (assuming C has no PHI nodes), but requires handling the merge instruction here.
421 // By adding a proxy node, we create a regular divergent shape which can easily be regularized later on.
422 // A -> D -> D1 -> C
423 // B -> D -> D2 -> C
424 //
425 // A, B, D belongs to the construct. D is the exit. D1 and D2 are empty.
426 //
427 // clang-format on
428 std::vector<Edge>
429 createAliasBlocksForComplexEdges(std::vector<Edge> Edges) {
430 std::unordered_set<BasicBlock *> Seen;
431 std::vector<Edge> Output;
432 Output.reserve(n: Edges.size());
433
434 for (auto &[Src, Dst] : Edges) {
435 auto [Iterator, Inserted] = Seen.insert(x: Src);
436 if (!Inserted) {
437 // Src already a source node. Cannot have 2 edges from A to B.
438 // Creating alias source block.
439 BasicBlock *NewSrc = BasicBlock::Create(
440 Context&: F.getContext(), Name: Src->getName() + ".new.src", Parent: &F);
441 replaceBranchTargets(BB: Src, OldTarget: Dst, NewTarget: NewSrc);
442 IRBuilder<> Builder(NewSrc);
443 Builder.CreateBr(Dest: Dst);
444 Src = NewSrc;
445 }
446
447 Output.emplace_back(args&: Src, args&: Dst);
448 }
449
450 return Output;
451 }
452
453 AllocaInst *CreateVariable(Function &F, Type *Type,
454 BasicBlock::iterator Position) {
455 const DataLayout &DL = F.getDataLayout();
456 return new AllocaInst(Type, DL.getAllocaAddrSpace(), nullptr, "reg",
457 Position);
458 }
459
460 // Given a construct defined by |Header|, and a list of exiting edges
461 // |Edges|, creates a new single exit node, fixing up those edges.
462 BasicBlock *createSingleExitNode(BasicBlock *Header,
463 std::vector<Edge> &Edges) {
464
465 std::vector<Edge> FixedEdges = createAliasBlocksForComplexEdges(Edges);
466
467 std::vector<BasicBlock *> Dsts;
468 std::unordered_map<BasicBlock *, ConstantInt *> DstToIndex;
469 auto NewExit = BasicBlock::Create(Context&: F.getContext(),
470 Name: Header->getName() + ".new.exit", Parent: &F);
471 IRBuilder<> ExitBuilder(NewExit);
472 for (auto &[Src, Dst] : FixedEdges) {
473 if (DstToIndex.count(x: Dst) != 0)
474 continue;
475 DstToIndex.emplace(args&: Dst, args: ExitBuilder.getInt32(C: DstToIndex.size()));
476 Dsts.push_back(x: Dst);
477 }
478
479 if (Dsts.size() == 1) {
480 for (auto &[Src, Dst] : FixedEdges) {
481 replaceBranchTargets(BB: Src, OldTarget: Dst, NewTarget: NewExit);
482 }
483 ExitBuilder.CreateBr(Dest: Dsts[0]);
484 return NewExit;
485 }
486
487 AllocaInst *Variable = CreateVariable(F, Type: ExitBuilder.getInt32Ty(),
488 Position: F.begin()->getFirstInsertionPt());
489 for (auto &[Src, Dst] : FixedEdges) {
490 IRBuilder<> B2(Src);
491 B2.SetInsertPoint(Src->getFirstInsertionPt());
492 B2.CreateStore(Val: DstToIndex[Dst], Ptr: Variable);
493 replaceBranchTargets(BB: Src, OldTarget: Dst, NewTarget: NewExit);
494 }
495
496 Value *Load = ExitBuilder.CreateLoad(Ty: ExitBuilder.getInt32Ty(), Ptr: Variable);
497
498 // If we can avoid an OpSwitch, generate an OpBranch. Reason is some
499 // OpBranch are allowed to exist without a new OpSelectionMerge if one of
500 // the branch is the parent's merge node, while OpSwitches are not.
501 if (Dsts.size() == 2) {
502 Value *Condition =
503 ExitBuilder.CreateCmp(Pred: CmpInst::ICMP_EQ, LHS: DstToIndex[Dsts[0]], RHS: Load);
504 ExitBuilder.CreateCondBr(Cond: Condition, True: Dsts[0], False: Dsts[1]);
505 return NewExit;
506 }
507
508 SwitchInst *Sw = ExitBuilder.CreateSwitch(V: Load, Dest: Dsts[0], NumCases: Dsts.size() - 1);
509 for (BasicBlock *BB : drop_begin(RangeOrContainer&: Dsts))
510 Sw->addCase(OnVal: DstToIndex[BB], Dest: BB);
511 return NewExit;
512 }
513 };
514
515 /// Create a value in BB set to the value associated with the branch the block
516 /// terminator will take.
517 Value *createExitVariable(
518 BasicBlock *BB,
519 const DenseMap<BasicBlock *, ConstantInt *> &TargetToValue) {
520 auto *T = BB->getTerminator();
521 if (isa<ReturnInst>(Val: T))
522 return nullptr;
523
524 IRBuilder<> Builder(BB);
525 Builder.SetInsertPoint(T);
526
527 if (auto *BI = dyn_cast<BranchInst>(Val: T)) {
528
529 BasicBlock *LHSTarget = BI->getSuccessor(i: 0);
530 BasicBlock *RHSTarget =
531 BI->isConditional() ? BI->getSuccessor(i: 1) : nullptr;
532
533 Value *LHS = TargetToValue.lookup(Val: LHSTarget);
534 Value *RHS = TargetToValue.lookup(Val: RHSTarget);
535
536 if (LHS == nullptr || RHS == nullptr)
537 return LHS == nullptr ? RHS : LHS;
538 return Builder.CreateSelect(C: BI->getCondition(), True: LHS, False: RHS);
539 }
540
541 // TODO: add support for switch cases.
542 llvm_unreachable("Unhandled terminator type.");
543 }
544
545 // Creates a new basic block in F with a single OpUnreachable instruction.
546 BasicBlock *CreateUnreachable(Function &F) {
547 BasicBlock *BB = BasicBlock::Create(Context&: F.getContext(), Name: "unreachable", Parent: &F);
548 IRBuilder<> Builder(BB);
549 Builder.CreateUnreachable();
550 return BB;
551 }
552
553 // Add OpLoopMerge instruction on cycles.
554 bool addMergeForLoops(Function &F) {
555 LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
556 auto *TopLevelRegion =
557 getAnalysis<SPIRVConvergenceRegionAnalysisWrapperPass>()
558 .getRegionInfo()
559 .getTopLevelRegion();
560
561 bool Modified = false;
562 for (auto &BB : F) {
563 // Not a loop header. Ignoring for now.
564 if (!LI.isLoopHeader(BB: &BB))
565 continue;
566 auto *L = LI.getLoopFor(BB: &BB);
567
568 // This loop header is not the entrance of a convergence region. Ignoring
569 // this block.
570 auto *CR = getRegionForHeader(Node: TopLevelRegion, BB: &BB);
571 if (CR == nullptr)
572 continue;
573
574 IRBuilder<> Builder(&BB);
575
576 auto *Merge = getExitFor(CR);
577 // We are indeed in a loop, but there are no exits (infinite loop).
578 // This could be caused by a bad shader, but also could be an artifact
579 // from an earlier optimization. It is not always clear if structurally
580 // reachable means runtime reachable, so we cannot error-out. What we must
581 // do however is to make is legal on the SPIR-V point of view, hence
582 // adding an unreachable merge block.
583 if (Merge == nullptr) {
584 BranchInst *Br = cast<BranchInst>(Val: BB.getTerminator());
585 assert(Br->isUnconditional());
586
587 Merge = CreateUnreachable(F);
588 Builder.SetInsertPoint(Br);
589 Builder.CreateCondBr(Cond: Builder.getFalse(), True: Merge, False: Br->getSuccessor(i: 0));
590 Br->eraseFromParent();
591 }
592
593 auto *Continue = L->getLoopLatch();
594
595 Builder.SetInsertPoint(BB.getTerminator());
596 auto MergeAddress = BlockAddress::get(F: Merge->getParent(), BB: Merge);
597 auto ContinueAddress = BlockAddress::get(F: Continue->getParent(), BB: Continue);
598 SmallVector<Value *, 2> Args = {MergeAddress, ContinueAddress};
599 SmallVector<unsigned, 1> LoopControlImms =
600 getSpirvLoopControlOperandsFromLoopMetadata(L);
601 for (unsigned Imm : LoopControlImms)
602 Args.emplace_back(Args: ConstantInt::get(Ty: Builder.getInt32Ty(), V: Imm));
603 Builder.CreateIntrinsic(ID: Intrinsic::spv_loop_merge, Args: {Args});
604 Modified = true;
605 }
606
607 return Modified;
608 }
609
610 // Adds an OpSelectionMerge to the immediate dominator or each node with an
611 // in-degree of 2 or more which is not already the merge target of an
612 // OpLoopMerge/OpSelectionMerge.
613 bool addMergeForNodesWithMultiplePredecessors(Function &F) {
614 DomTreeBuilder::BBDomTree DT;
615 DT.recalculate(Func&: F);
616
617 bool Modified = false;
618 for (auto &BB : F) {
619 if (pred_size(BB: &BB) <= 1)
620 continue;
621
622 if (hasLoopMergeInstruction(BB) && pred_size(BB: &BB) <= 2)
623 continue;
624
625 assert(DT.getNode(&BB)->getIDom());
626 BasicBlock *Header = DT.getNode(BB: &BB)->getIDom()->getBlock();
627
628 if (isDefinedAsSelectionMergeBy(Header&: *Header, Merge&: BB))
629 continue;
630
631 IRBuilder<> Builder(Header);
632 Builder.SetInsertPoint(Header->getTerminator());
633
634 auto MergeAddress = BlockAddress::get(F: BB.getParent(), BB: &BB);
635 createOpSelectMerge(Builder: &Builder, MergeAddress);
636
637 Modified = true;
638 }
639
640 return Modified;
641 }
642
643 // When a block has multiple OpSelectionMerge/OpLoopMerge instructions, sorts
644 // them to put the "largest" first. A merge instruction is defined as larger
645 // than another when its target merge block post-dominates the other target's
646 // merge block. (This ordering should match the nesting ordering of the source
647 // HLSL).
648 bool sortSelectionMerge(Function &F, BasicBlock &Block) {
649 std::vector<Instruction *> MergeInstructions;
650 for (Instruction &I : Block)
651 if (isMergeInstruction(I: &I))
652 MergeInstructions.push_back(x: &I);
653
654 if (MergeInstructions.size() <= 1)
655 return false;
656
657 Instruction *InsertionPoint = *MergeInstructions.begin();
658
659 PartialOrderingVisitor Visitor(F);
660 std::sort(first: MergeInstructions.begin(), last: MergeInstructions.end(),
661 comp: [&Visitor](Instruction *Left, Instruction *Right) {
662 if (Left == Right)
663 return false;
664 BasicBlock *RightMerge = getDesignatedMergeBlock(I: Right);
665 BasicBlock *LeftMerge = getDesignatedMergeBlock(I: Left);
666 return !Visitor.compare(LHS: RightMerge, RHS: LeftMerge);
667 });
668
669 for (Instruction *I : MergeInstructions) {
670 I->moveBefore(InsertPos: InsertionPoint->getIterator());
671 InsertionPoint = I;
672 }
673
674 return true;
675 }
676
677 // Sorts selection merge headers in |F|.
678 // A is sorted before B if the merge block designated by B is an ancestor of
679 // the one designated by A.
680 bool sortSelectionMergeHeaders(Function &F) {
681 bool Modified = false;
682 for (BasicBlock &BB : F) {
683 Modified |= sortSelectionMerge(F, Block&: BB);
684 }
685 return Modified;
686 }
687
688 // Split basic blocks containing multiple OpLoopMerge/OpSelectionMerge
689 // instructions so each basic block contains only a single merge instruction.
690 bool splitBlocksWithMultipleHeaders(Function &F) {
691 std::stack<BasicBlock *> Work;
692 for (auto &BB : F) {
693 std::vector<Instruction *> MergeInstructions = getMergeInstructions(BB);
694 if (MergeInstructions.size() <= 1)
695 continue;
696 Work.push(x: &BB);
697 }
698
699 const bool Modified = Work.size() > 0;
700 while (Work.size() > 0) {
701 BasicBlock *Header = Work.top();
702 Work.pop();
703
704 std::vector<Instruction *> MergeInstructions =
705 getMergeInstructions(BB&: *Header);
706 for (unsigned i = 1; i < MergeInstructions.size(); i++) {
707 BasicBlock *NewBlock =
708 Header->splitBasicBlock(I: MergeInstructions[i], BBName: "new.header");
709
710 if (getDesignatedContinueBlock(I: MergeInstructions[0]) == nullptr) {
711 BasicBlock *Unreachable = CreateUnreachable(F);
712
713 BranchInst *BI = cast<BranchInst>(Val: Header->getTerminator());
714 IRBuilder<> Builder(Header);
715 Builder.SetInsertPoint(BI);
716 Builder.CreateCondBr(Cond: Builder.getTrue(), True: NewBlock, False: Unreachable);
717 BI->eraseFromParent();
718 }
719
720 Header = NewBlock;
721 }
722 }
723
724 return Modified;
725 }
726
727 // Adds an OpSelectionMerge to each block with an out-degree >= 2 which
728 // doesn't already have an OpSelectionMerge.
729 bool addMergeForDivergentBlocks(Function &F) {
730 DomTreeBuilder::BBPostDomTree PDT;
731 PDT.recalculate(Func&: F);
732 bool Modified = false;
733
734 auto MergeBlocks = getMergeBlocks(F);
735 auto ContinueBlocks = getContinueBlocks(F);
736
737 for (auto &BB : F) {
738 if (getMergeInstructions(BB).size() != 0)
739 continue;
740
741 std::vector<BasicBlock *> Candidates;
742 for (BasicBlock *Successor : successors(BB: &BB)) {
743 if (MergeBlocks.contains(Ptr: Successor))
744 continue;
745 if (ContinueBlocks.contains(Ptr: Successor))
746 continue;
747 Candidates.push_back(x: Successor);
748 }
749
750 if (Candidates.size() <= 1)
751 continue;
752
753 Modified = true;
754 BasicBlock *Merge = Candidates[0];
755
756 auto MergeAddress = BlockAddress::get(F: Merge->getParent(), BB: Merge);
757 IRBuilder<> Builder(&BB);
758 Builder.SetInsertPoint(BB.getTerminator());
759 createOpSelectMerge(Builder: &Builder, MergeAddress);
760 }
761
762 return Modified;
763 }
764
765 // Gather all the exit nodes for the construct header by |Header| and
766 // containing the blocks |Construct|.
767 std::vector<Edge> getExitsFrom(const BlockSet &Construct,
768 BasicBlock &Header) {
769 std::vector<Edge> Output;
770 visit(Start&: Header, op: [&](BasicBlock *Item) {
771 if (Construct.count(x: Item) == 0)
772 return false;
773
774 for (BasicBlock *Successor : successors(BB: Item)) {
775 if (Construct.count(x: Successor) == 0)
776 Output.emplace_back(args&: Item, args&: Successor);
777 }
778 return true;
779 });
780
781 return Output;
782 }
783
784 // Build a divergent construct tree searching from |BB|.
785 // If |Parent| is not null, this tree is attached to the parent's tree.
786 void constructDivergentConstruct(BlockSet &Visited, Splitter &S,
787 BasicBlock *BB, DivergentConstruct *Parent) {
788 if (Visited.count(x: BB) != 0)
789 return;
790 Visited.insert(x: BB);
791
792 auto MIS = getMergeInstructions(BB&: *BB);
793 if (MIS.size() == 0) {
794 for (BasicBlock *Successor : successors(BB))
795 constructDivergentConstruct(Visited, S, BB: Successor, Parent);
796 return;
797 }
798
799 assert(MIS.size() == 1);
800 Instruction *MI = MIS[0];
801
802 BasicBlock *Merge = getDesignatedMergeBlock(I: MI);
803 BasicBlock *Continue = getDesignatedContinueBlock(I: MI);
804
805 auto Output = std::make_unique<DivergentConstruct>();
806 Output->Header = BB;
807 Output->Merge = Merge;
808 Output->Continue = Continue;
809 Output->Parent = Parent;
810
811 constructDivergentConstruct(Visited, S, BB: Merge, Parent);
812 if (Continue)
813 constructDivergentConstruct(Visited, S, BB: Continue, Parent: Output.get());
814
815 for (BasicBlock *Successor : successors(BB))
816 constructDivergentConstruct(Visited, S, BB: Successor, Parent: Output.get());
817
818 if (Parent)
819 Parent->Children.emplace_back(args: std::move(Output));
820 }
821
822 // Returns the blocks belonging to the divergent construct |Node|.
823 BlockSet getConstructBlocks(Splitter &S, DivergentConstruct *Node) {
824 assert(Node->Header && Node->Merge);
825
826 if (Node->Continue) {
827 auto LoopBlocks = S.getLoopConstructBlocks(Header: Node->Header, Merge: Node->Merge);
828 return BlockSet(LoopBlocks.begin(), LoopBlocks.end());
829 }
830
831 auto SelectionBlocks = S.getSelectionConstructBlocks(Node);
832 return BlockSet(SelectionBlocks.begin(), SelectionBlocks.end());
833 }
834
835 // Fixup the construct |Node| to respect a set of rules defined by the SPIR-V
836 // spec.
837 bool fixupConstruct(Splitter &S, DivergentConstruct *Node) {
838 bool Modified = false;
839 for (auto &Child : Node->Children)
840 Modified |= fixupConstruct(S, Node: Child.get());
841
842 // This construct is the root construct. Does not represent any real
843 // construct, just a way to access the first level of the forest.
844 if (Node->Parent == nullptr)
845 return Modified;
846
847 // This node's parent is the root. Meaning this is a top-level construct.
848 // There can be multiple exists, but all are guaranteed to exit at most 1
849 // construct since we are at first level.
850 if (Node->Parent->Header == nullptr)
851 return Modified;
852
853 // Health check for the structure.
854 assert(Node->Header && Node->Merge);
855 assert(Node->Parent->Header && Node->Parent->Merge);
856
857 BlockSet ConstructBlocks = getConstructBlocks(S, Node);
858 auto Edges = getExitsFrom(Construct: ConstructBlocks, Header&: *Node->Header);
859
860 // No edges exiting the construct.
861 if (Edges.size() < 1)
862 return Modified;
863
864 bool HasBadEdge = Node->Merge == Node->Parent->Merge ||
865 Node->Merge == Node->Parent->Continue;
866 // BasicBlock *Target = Edges[0].second;
867 for (auto &[Src, Dst] : Edges) {
868 // - Breaking from a selection construct: S is a selection construct, S is
869 // the innermost structured
870 // control-flow construct containing A, and B is the merge block for S
871 // - Breaking from the innermost loop: S is the innermost loop construct
872 // containing A,
873 // and B is the merge block for S
874 if (Node->Merge == Dst)
875 continue;
876
877 // Entering the innermost loop’s continue construct: S is the innermost
878 // loop construct containing A, and B is the continue target for S
879 if (Node->Continue == Dst)
880 continue;
881
882 // TODO: what about cases branching to another case in the switch? Seems
883 // to work, but need to double check.
884 HasBadEdge = true;
885 }
886
887 if (!HasBadEdge)
888 return Modified;
889
890 // Create a single exit node gathering all exit edges.
891 BasicBlock *NewExit = S.createSingleExitNode(Header: Node->Header, Edges);
892
893 // Fixup this construct's merge node to point to the new exit.
894 // Note: this algorithm fixes inner-most divergence construct first. So
895 // recursive structures sharing a single merge node are fixed from the
896 // inside toward the outside.
897 auto MergeInstructions = getMergeInstructions(BB&: *Node->Header);
898 assert(MergeInstructions.size() == 1);
899 Instruction *I = MergeInstructions[0];
900 BlockAddress *BA = cast<BlockAddress>(Val: I->getOperand(i: 0));
901 if (BA->getBasicBlock() == Node->Merge) {
902 auto MergeAddress = BlockAddress::get(F: NewExit->getParent(), BB: NewExit);
903 I->setOperand(i: 0, Val: MergeAddress);
904 }
905
906 // Clean up of the possible dangling BockAddr operands to prevent MIR
907 // comments about "address of removed block taken".
908 if (!BA->isConstantUsed())
909 BA->destroyConstant();
910
911 Node->Merge = NewExit;
912 // Regenerate the dom trees.
913 S.invalidate();
914 return true;
915 }
916
917 bool splitCriticalEdges(Function &F) {
918 LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
919 Splitter S(F, LI);
920
921 DivergentConstruct Root;
922 BlockSet Visited;
923 constructDivergentConstruct(Visited, S, BB: &*F.begin(), Parent: &Root);
924 return fixupConstruct(S, Node: &Root);
925 }
926
927 // Simplify branches when possible:
928 // - if the 2 sides of a conditional branch are the same, transforms it to an
929 // unconditional branch.
930 // - if a switch has only 2 distinct successors, converts it to a conditional
931 // branch.
932 bool simplifyBranches(Function &F) {
933 bool Modified = false;
934
935 for (BasicBlock &BB : F) {
936 SwitchInst *SI = dyn_cast<SwitchInst>(Val: BB.getTerminator());
937 if (!SI)
938 continue;
939 if (SI->getNumCases() > 1)
940 continue;
941
942 Modified = true;
943 IRBuilder<> Builder(&BB);
944 Builder.SetInsertPoint(SI);
945
946 if (SI->getNumCases() == 0) {
947 Builder.CreateBr(Dest: SI->getDefaultDest());
948 } else {
949 Value *Condition =
950 Builder.CreateCmp(Pred: CmpInst::ICMP_EQ, LHS: SI->getCondition(),
951 RHS: SI->case_begin()->getCaseValue());
952 Builder.CreateCondBr(Cond: Condition, True: SI->case_begin()->getCaseSuccessor(),
953 False: SI->getDefaultDest());
954 }
955 SI->eraseFromParent();
956 }
957
958 return Modified;
959 }
960
961 // Makes sure every case target in |F| is unique. If 2 cases branch to the
962 // same basic block, one of the targets is updated so it jumps to a new basic
963 // block ending with a single unconditional branch to the original target.
964 bool splitSwitchCases(Function &F) {
965 bool Modified = false;
966
967 for (BasicBlock &BB : F) {
968 SwitchInst *SI = dyn_cast<SwitchInst>(Val: BB.getTerminator());
969 if (!SI)
970 continue;
971
972 BlockSet Seen;
973 Seen.insert(x: SI->getDefaultDest());
974
975 auto It = SI->case_begin();
976 while (It != SI->case_end()) {
977 BasicBlock *Target = It->getCaseSuccessor();
978 if (Seen.count(x: Target) == 0) {
979 Seen.insert(x: Target);
980 ++It;
981 continue;
982 }
983
984 Modified = true;
985 BasicBlock *NewTarget =
986 BasicBlock::Create(Context&: F.getContext(), Name: "new.sw.case", Parent: &F);
987 IRBuilder<> Builder(NewTarget);
988 Builder.CreateBr(Dest: Target);
989 SI->addCase(OnVal: It->getCaseValue(), Dest: NewTarget);
990 It = SI->removeCase(I: It);
991 }
992 }
993
994 return Modified;
995 }
996
997 // Removes blocks not contributing to any structured CFG. This assumes there
998 // is no PHI nodes.
999 bool removeUselessBlocks(Function &F) {
1000 std::vector<BasicBlock *> ToRemove;
1001
1002 auto MergeBlocks = getMergeBlocks(F);
1003 auto ContinueBlocks = getContinueBlocks(F);
1004
1005 for (BasicBlock &BB : F) {
1006 if (BB.size() != 1)
1007 continue;
1008
1009 if (isa<ReturnInst>(Val: BB.getTerminator()))
1010 continue;
1011
1012 if (MergeBlocks.count(Ptr: &BB) != 0 || ContinueBlocks.count(Ptr: &BB) != 0)
1013 continue;
1014
1015 if (BB.getUniqueSuccessor() == nullptr)
1016 continue;
1017
1018 BasicBlock *Successor = BB.getUniqueSuccessor();
1019 std::vector<BasicBlock *> Predecessors(predecessors(BB: &BB).begin(),
1020 predecessors(BB: &BB).end());
1021 for (BasicBlock *Predecessor : Predecessors)
1022 replaceBranchTargets(BB: Predecessor, OldTarget: &BB, NewTarget: Successor);
1023 ToRemove.push_back(x: &BB);
1024 }
1025
1026 for (BasicBlock *BB : ToRemove)
1027 BB->eraseFromParent();
1028
1029 return ToRemove.size() != 0;
1030 }
1031
1032 bool addHeaderToRemainingDivergentDAG(Function &F) {
1033 bool Modified = false;
1034
1035 auto MergeBlocks = getMergeBlocks(F);
1036 auto ContinueBlocks = getContinueBlocks(F);
1037 auto HeaderBlocks = getHeaderBlocks(F);
1038
1039 DomTreeBuilder::BBDomTree DT;
1040 DomTreeBuilder::BBPostDomTree PDT;
1041 PDT.recalculate(Func&: F);
1042 DT.recalculate(Func&: F);
1043
1044 for (BasicBlock &BB : F) {
1045 if (HeaderBlocks.count(Ptr: &BB) != 0)
1046 continue;
1047 if (succ_size(BB: &BB) < 2)
1048 continue;
1049
1050 size_t CandidateEdges = 0;
1051 for (BasicBlock *Successor : successors(BB: &BB)) {
1052 if (MergeBlocks.count(Ptr: Successor) != 0 ||
1053 ContinueBlocks.count(Ptr: Successor) != 0)
1054 continue;
1055 if (HeaderBlocks.count(Ptr: Successor) != 0)
1056 continue;
1057 CandidateEdges += 1;
1058 }
1059
1060 if (CandidateEdges <= 1)
1061 continue;
1062
1063 BasicBlock *Header = &BB;
1064 BasicBlock *Merge = PDT.getNode(BB: &BB)->getIDom()->getBlock();
1065
1066 bool HasBadBlock = false;
1067 visit(Start&: *Header, op: [&](const BasicBlock *Node) {
1068 if (DT.dominates(A: Header, B: Node))
1069 return false;
1070 if (PDT.dominates(A: Merge, B: Node))
1071 return false;
1072 if (Node == Header || Node == Merge)
1073 return true;
1074
1075 HasBadBlock |= MergeBlocks.count(Ptr: Node) != 0 ||
1076 ContinueBlocks.count(Ptr: Node) != 0 ||
1077 HeaderBlocks.count(Ptr: Node) != 0;
1078 return !HasBadBlock;
1079 });
1080
1081 if (HasBadBlock)
1082 continue;
1083
1084 Modified = true;
1085
1086 if (Merge == nullptr) {
1087 Merge = *successors(BB: Header).begin();
1088 IRBuilder<> Builder(Header);
1089 Builder.SetInsertPoint(Header->getTerminator());
1090
1091 auto MergeAddress = BlockAddress::get(F: Merge->getParent(), BB: Merge);
1092 createOpSelectMerge(Builder: &Builder, MergeAddress);
1093 continue;
1094 }
1095
1096 Instruction *SplitInstruction = Merge->getTerminator();
1097 if (isMergeInstruction(I: SplitInstruction->getPrevNode()))
1098 SplitInstruction = SplitInstruction->getPrevNode();
1099 BasicBlock *NewMerge =
1100 Merge->splitBasicBlockBefore(I: SplitInstruction, BBName: "new.merge");
1101
1102 IRBuilder<> Builder(Header);
1103 Builder.SetInsertPoint(Header->getTerminator());
1104
1105 auto MergeAddress = BlockAddress::get(F: NewMerge->getParent(), BB: NewMerge);
1106 createOpSelectMerge(Builder: &Builder, MergeAddress);
1107 }
1108
1109 return Modified;
1110 }
1111
1112public:
1113 static char ID;
1114
1115 SPIRVStructurizer() : FunctionPass(ID) {}
1116
1117 virtual bool runOnFunction(Function &F) override {
1118 bool Modified = false;
1119
1120 // In LLVM, Switches are allowed to have several cases branching to the same
1121 // basic block. This is allowed in SPIR-V, but can make structurizing SPIR-V
1122 // harder, so first remove edge cases.
1123 Modified |= splitSwitchCases(F);
1124
1125 // LLVM allows conditional branches to have both side jumping to the same
1126 // block. It also allows switched to have a single default, or just one
1127 // case. Cleaning this up now.
1128 Modified |= simplifyBranches(F);
1129
1130 // At this state, we should have a reducible CFG with cycles.
1131 // STEP 1: Adding OpLoopMerge instructions to loop headers.
1132 Modified |= addMergeForLoops(F);
1133
1134 // STEP 2: adding OpSelectionMerge to each node with an in-degree >= 2.
1135 Modified |= addMergeForNodesWithMultiplePredecessors(F);
1136
1137 // STEP 3:
1138 // Sort selection merge, the largest construct goes first.
1139 // This simplifies the next step.
1140 Modified |= sortSelectionMergeHeaders(F);
1141
1142 // STEP 4: As this stage, we can have a single basic block with multiple
1143 // OpLoopMerge/OpSelectionMerge instructions. Splitting this block so each
1144 // BB has a single merge instruction.
1145 Modified |= splitBlocksWithMultipleHeaders(F);
1146
1147 // STEP 5: In the previous steps, we added merge blocks the loops and
1148 // natural merge blocks (in-degree >= 2). What remains are conditions with
1149 // an exiting branch (return, unreachable). In such case, we must start from
1150 // the header, and add headers to divergent construct with no headers.
1151 Modified |= addMergeForDivergentBlocks(F);
1152
1153 // STEP 6: At this stage, we have several divergent construct defines by a
1154 // header and a merge block. But their boundaries have no constraints: a
1155 // construct exit could be outside of the parents' construct exit. Such
1156 // edges are called critical edges. What we need is to split those edges
1157 // into several parts. Each part exiting the parent's construct by its merge
1158 // block.
1159 Modified |= splitCriticalEdges(F);
1160
1161 // STEP 7: The previous steps possibly created a lot of "proxy" blocks.
1162 // Blocks with a single unconditional branch, used to create a valid
1163 // divergent construct tree. Some nodes are still requires (e.g: nodes
1164 // allowing a valid exit through the parent's merge block). But some are
1165 // left-overs of past transformations, and could cause actual validation
1166 // issues. E.g: the SPIR-V spec allows a construct to break to the parents
1167 // loop construct without an OpSelectionMerge, but this requires a straight
1168 // jump. If a proxy block lies between the conditional branch and the
1169 // parent's merge, the CFG is not valid.
1170 Modified |= removeUselessBlocks(F);
1171
1172 // STEP 8: Final fix-up steps: our tree boundaries are correct, but some
1173 // blocks are branching with no header. Those are often simple conditional
1174 // branches with 1 or 2 returning edges. Adding a header for those.
1175 Modified |= addHeaderToRemainingDivergentDAG(F);
1176
1177 // STEP 9: sort basic blocks to match both the LLVM & SPIR-V requirements.
1178 Modified |= sortBlocks(F);
1179
1180 return Modified;
1181 }
1182
1183 void getAnalysisUsage(AnalysisUsage &AU) const override {
1184 AU.addRequired<DominatorTreeWrapperPass>();
1185 AU.addRequired<LoopInfoWrapperPass>();
1186 AU.addRequired<SPIRVConvergenceRegionAnalysisWrapperPass>();
1187
1188 AU.addPreserved<SPIRVConvergenceRegionAnalysisWrapperPass>();
1189 FunctionPass::getAnalysisUsage(AU);
1190 }
1191
1192 void createOpSelectMerge(IRBuilder<> *Builder, BlockAddress *MergeAddress) {
1193 Instruction *BBTerminatorInst = Builder->GetInsertBlock()->getTerminator();
1194
1195 MDNode *MDNode = BBTerminatorInst->getMetadata(Kind: "hlsl.controlflow.hint");
1196
1197 ConstantInt *BranchHint = ConstantInt::get(Ty: Builder->getInt32Ty(), V: 0);
1198
1199 if (MDNode) {
1200 assert(MDNode->getNumOperands() == 2 &&
1201 "invalid metadata hlsl.controlflow.hint");
1202 BranchHint = mdconst::extract<ConstantInt>(MD: MDNode->getOperand(I: 1));
1203 }
1204
1205 SmallVector<Value *, 2> Args = {MergeAddress, BranchHint};
1206
1207 Builder->CreateIntrinsic(ID: Intrinsic::spv_selection_merge,
1208 Types: {MergeAddress->getType()}, Args);
1209 }
1210};
1211} // anonymous namespace
1212
1213char SPIRVStructurizer::ID = 0;
1214
1215INITIALIZE_PASS_BEGIN(SPIRVStructurizer, "spirv-structurizer",
1216 "structurize SPIRV", false, false)
1217INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
1218INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1219INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
1220INITIALIZE_PASS_DEPENDENCY(SPIRVConvergenceRegionAnalysisWrapperPass)
1221
1222INITIALIZE_PASS_END(SPIRVStructurizer, "spirv-structurizer",
1223 "structurize SPIRV", false, false)
1224
1225FunctionPass *llvm::createSPIRVStructurizerPass() {
1226 return new SPIRVStructurizer();
1227}
1228
1229PreservedAnalyses SPIRVStructurizerWrapper::run(Function &F,
1230 FunctionAnalysisManager &AF) {
1231
1232 auto FPM = legacy::FunctionPassManager(F.getParent());
1233 FPM.add(P: createSPIRVStructurizerPass());
1234
1235 if (!FPM.run(F))
1236 return PreservedAnalyses::all();
1237 PreservedAnalyses PA;
1238 PA.preserveSet<CFGAnalyses>();
1239 return PA;
1240}
1241