lib/Target/NVPTX/NVPTXLowerAlloca.cpp

   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 BasicBlockPass {
  45   bool runOnBasicBlock(BasicBlock &BB) override;
  46
  47 public:
  48   static char ID; // Pass identification, replacement for typeid
  49   NVPTXLowerAlloca() : BasicBlockPass(ID) {}
  50   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 // =============================================================================
  64 bool NVPTXLowerAlloca::runOnBasicBlock(BasicBlock &BB) {
  65   if (skipBasicBlock(BB))
  66     return false;
  67
  68   bool Changed = false;
  69   for (auto &I : BB) {
  70     if (auto allocaInst = dyn_cast<AllocaInst>(&I)) {
  71       Changed = true;
  72       auto PTy = dyn_cast<PointerType>(allocaInst->getType());
  73       auto ETy = PTy->getElementType();
  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 = new AddrSpaceCastInst(NewASCToLocal,
  78                                                     GenericAddrTy, "");
  79       NewASCToLocal->insertAfter(allocaInst);
  80       NewASCToGeneric->insertAfter(NewASCToLocal);
  81       for (Value::use_iterator UI = allocaInst->use_begin(),
  82                                 UE = allocaInst->use_end();
  83             UI != UE; ) {
  84         // Check Load, Store, GEP, and BitCast Uses on alloca and make them
  85         // use the converted generic address, in order to expose non-generic
  86         // addrspacecast to NVPTXInferAddressSpaces. For other types
  87         // of instructions this is unnecessary and may introduce redundant
  88         // address cast.
  89         const auto &AllocaUse = *UI++;
  90         auto LI = dyn_cast<LoadInst>(AllocaUse.getUser());
  91         if (LI && LI->getPointerOperand() == allocaInst && !LI->isVolatile()) {
  92           LI->setOperand(LI->getPointerOperandIndex(), NewASCToGeneric);
  93           continue;
  94         }
  95         auto SI = dyn_cast<StoreInst>(AllocaUse.getUser());
  96         if (SI && SI->getPointerOperand() == allocaInst && !SI->isVolatile()) {
  97           SI->setOperand(SI->getPointerOperandIndex(), NewASCToGeneric);
  98           continue;
  99         }
 100         auto GI = dyn_cast<GetElementPtrInst>(AllocaUse.getUser());
 101         if (GI && GI->getPointerOperand() == allocaInst) {
 102           GI->setOperand(GI->getPointerOperandIndex(), NewASCToGeneric);
 103           continue;
 104         }
 105         auto BI = dyn_cast<BitCastInst>(AllocaUse.getUser());
 106         if (BI && BI->getOperand(0) == allocaInst) {
 107           BI->setOperand(0, NewASCToGeneric);
 108           continue;
 109         }
 110       }
 111     }
 112   }
 113   return Changed;
 114 }
 115
 116 BasicBlockPass *llvm::createNVPTXLowerAllocaPass() {
 117   return new NVPTXLowerAlloca();
 118 }