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
37 using namespace llvm;
38
39 namespace llvm {
40 void initializeNVPTXLowerAllocaPass(PassRegistry &);
41 }
42
43 namespace {
44 class NVPTXLowerAlloca : public FunctionPass {
45 bool runOnFunction(Function &F) override;
46
47 public:
48 static char ID; // Pass identification, replacement for typeid
NVPTXLowerAlloca()49 NVPTXLowerAlloca() : FunctionPass(ID) {}
getPassName() const50 StringRef getPassName() const override {
51 return "convert address space of alloca'ed memory to local";
52 }
53 };
54 } // namespace
55
56 char NVPTXLowerAlloca::ID = 1;
57
58 INITIALIZE_PASS(NVPTXLowerAlloca, "nvptx-lower-alloca",
59 "Lower Alloca", false, false)
60
61 // =============================================================================
62 // Main function for this pass.
63 // =============================================================================
runOnFunction(Function & F)64 bool 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>(&I)) {
72 Changed = true;
73 auto ETy = allocaInst->getAllocatedType();
74 auto LocalAddrTy = PointerType::get(ETy, ADDRESS_SPACE_LOCAL);
75 auto NewASCToLocal = new AddrSpaceCastInst(allocaInst, LocalAddrTy, "");
76 auto GenericAddrTy = PointerType::get(ETy, ADDRESS_SPACE_GENERIC);
77 auto NewASCToGeneric =
78 new AddrSpaceCastInst(NewASCToLocal, GenericAddrTy, "");
79 NewASCToLocal->insertAfter(allocaInst);
80 NewASCToGeneric->insertAfter(NewASCToLocal);
81 for (Use &AllocaUse : llvm::make_early_inc_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>(AllocaUse.getUser());
88 if (LI && LI->getPointerOperand() == allocaInst &&
89 !LI->isVolatile()) {
90 LI->setOperand(LI->getPointerOperandIndex(), NewASCToGeneric);
91 continue;
92 }
93 auto SI = dyn_cast<StoreInst>(AllocaUse.getUser());
94 if (SI && SI->getPointerOperand() == allocaInst &&
95 !SI->isVolatile()) {
96 SI->setOperand(SI->getPointerOperandIndex(), NewASCToGeneric);
97 continue;
98 }
99 auto GI = dyn_cast<GetElementPtrInst>(AllocaUse.getUser());
100 if (GI && GI->getPointerOperand() == allocaInst) {
101 GI->setOperand(GI->getPointerOperandIndex(), NewASCToGeneric);
102 continue;
103 }
104 auto BI = dyn_cast<BitCastInst>(AllocaUse.getUser());
105 if (BI && BI->getOperand(0) == allocaInst) {
106 BI->setOperand(0, NewASCToGeneric);
107 continue;
108 }
109 }
110 }
111 }
112 return Changed;
113 }
114
createNVPTXLowerAllocaPass()115 FunctionPass *llvm::createNVPTXLowerAllocaPass() {
116 return new NVPTXLowerAlloca();
117 }
118