1//===-- NVPTXLowerAlloca.cpp - Make alloca to use local memory =====--===//
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// For all alloca instructions, and add a pair of cast to local address for
10// each of them. For example,
11//
12// %A = alloca i32
13// store i32 0, i32* %A ; emits st.u32
14//
15// will be transformed to
16//
17// %A = alloca i32
18// %Local = addrspacecast i32* %A to i32 addrspace(5)*
19// %Generic = addrspacecast i32 addrspace(5)* %A to i32*
20// store i32 0, i32 addrspace(5)* %Generic ; emits st.local.u32
21//
22// And we will rely on NVPTXInferAddressSpaces to combine the last two
23// instructions.
24//
25//===----------------------------------------------------------------------===//
26
27#include "NVPTX.h"
28#include "NVPTXUtilities.h"
29#include "MCTargetDesc/NVPTXBaseInfo.h"
30#include "llvm/IR/Function.h"
31#include "llvm/IR/Instructions.h"
32#include "llvm/IR/IntrinsicInst.h"
33#include "llvm/IR/Module.h"
34#include "llvm/IR/Type.h"
35#include "llvm/Pass.h"
36
37using namespace llvm;
38
39namespace llvm {
40void initializeNVPTXLowerAllocaPass(PassRegistry &);
41}
42
43namespace {
44class NVPTXLowerAlloca : public FunctionPass {
45 bool runOnFunction(Function &F) override;
46
47public:
48 static char ID; // Pass identification, replacement for typeid
49 NVPTXLowerAlloca() : FunctionPass(ID) {}
50 StringRef getPassName() const override {
51 return "convert address space of alloca'ed memory to local";
52 }
53};
54} // namespace
55
56char NVPTXLowerAlloca::ID = 1;
57
58INITIALIZE_PASS(NVPTXLowerAlloca, "nvptx-lower-alloca",
59 "Lower Alloca", false, false)
60
61// =============================================================================
62// Main function for this pass.
63// =============================================================================
64bool NVPTXLowerAlloca::runOnFunction(Function &F) {
65 if (skipFunction(F))
66 return false;
67
68 bool Changed = false;
69 for (auto &BB : F)
70 for (auto &I : BB) {
71 if (auto allocaInst = dyn_cast<AllocaInst>(Val: &I)) {
72 Changed = true;
73 auto ETy = allocaInst->getAllocatedType();
74 auto LocalAddrTy = PointerType::get(ElementType: ETy, AddressSpace: ADDRESS_SPACE_LOCAL);
75 auto NewASCToLocal = new AddrSpaceCastInst(allocaInst, LocalAddrTy, "");
76 auto GenericAddrTy = PointerType::get(ElementType: ETy, AddressSpace: ADDRESS_SPACE_GENERIC);
77 auto NewASCToGeneric =
78 new AddrSpaceCastInst(NewASCToLocal, GenericAddrTy, "");
79 NewASCToLocal->insertAfter(InsertPos: allocaInst);
80 NewASCToGeneric->insertAfter(InsertPos: NewASCToLocal);
81 for (Use &AllocaUse : llvm::make_early_inc_range(Range: allocaInst->uses())) {
82 // Check Load, Store, GEP, and BitCast Uses on alloca and make them
83 // use the converted generic address, in order to expose non-generic
84 // addrspacecast to NVPTXInferAddressSpaces. For other types
85 // of instructions this is unnecessary and may introduce redundant
86 // address cast.
87 auto LI = dyn_cast<LoadInst>(Val: AllocaUse.getUser());
88 if (LI && LI->getPointerOperand() == allocaInst &&
89 !LI->isVolatile()) {
90 LI->setOperand(i_nocapture: LI->getPointerOperandIndex(), Val_nocapture: NewASCToGeneric);
91 continue;
92 }
93 auto SI = dyn_cast<StoreInst>(Val: AllocaUse.getUser());
94 if (SI && SI->getPointerOperand() == allocaInst &&
95 !SI->isVolatile()) {
96 SI->setOperand(i_nocapture: SI->getPointerOperandIndex(), Val_nocapture: NewASCToGeneric);
97 continue;
98 }
99 auto GI = dyn_cast<GetElementPtrInst>(Val: AllocaUse.getUser());
100 if (GI && GI->getPointerOperand() == allocaInst) {
101 GI->setOperand(i_nocapture: GI->getPointerOperandIndex(), Val_nocapture: NewASCToGeneric);
102 continue;
103 }
104 auto BI = dyn_cast<BitCastInst>(Val: AllocaUse.getUser());
105 if (BI && BI->getOperand(i_nocapture: 0) == allocaInst) {
106 BI->setOperand(i_nocapture: 0, Val_nocapture: NewASCToGeneric);
107 continue;
108 }
109 }
110 }
111 }
112 return Changed;
113}
114
115FunctionPass *llvm::createNVPTXLowerAllocaPass() {
116 return new NVPTXLowerAlloca();
117}
118