lib/CodeGen/PreISelIntrinsicLowering.cpp

   1 //===- PreISelIntrinsicLowering.cpp - Pre-ISel intrinsic lowering pass ----===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This pass implements IR lowering for the llvm.load.relative intrinsic.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/CodeGen/PreISelIntrinsicLowering.h"
  15 #include "llvm/CodeGen/Passes.h"
  16 #include "llvm/IR/Function.h"
  17 #include "llvm/IR/IRBuilder.h"
  18 #include "llvm/IR/Instructions.h"
  19 #include "llvm/IR/Module.h"
  20 #include "llvm/IR/Type.h"
  21 #include "llvm/IR/User.h"
  22 #include "llvm/Pass.h"
  23 #include "llvm/Support/Casting.h"
  24
  25 using namespace llvm;
  26
  27 static bool lowerLoadRelative(Function &F) {
  28   if (F.use_empty())
  29     return false;
  30
  31   bool Changed = false;
  32   Type *Int32Ty = Type::getInt32Ty(F.getContext());
  33   Type *Int32PtrTy = Int32Ty->getPointerTo();
  34   Type *Int8Ty = Type::getInt8Ty(F.getContext());
  35
  36   for (auto I = F.use_begin(), E = F.use_end(); I != E;) {
  37     auto CI = dyn_cast<CallInst>(I->getUser());
  38     ++I;
  39     if (!CI || CI->getCalledValue() != &F)
  40       continue;
  41
  42     IRBuilder<> B(CI);
  43     Value *OffsetPtr =
  44         B.CreateGEP(Int8Ty, CI->getArgOperand(0), CI->getArgOperand(1));
  45     Value *OffsetPtrI32 = B.CreateBitCast(OffsetPtr, Int32PtrTy);
  46     Value *OffsetI32 = B.CreateAlignedLoad(OffsetPtrI32, 4);
  47
  48     Value *ResultPtr = B.CreateGEP(Int8Ty, CI->getArgOperand(0), OffsetI32);
  49
  50     CI->replaceAllUsesWith(ResultPtr);
  51     CI->eraseFromParent();
  52     Changed = true;
  53   }
  54
  55   return Changed;
  56 }
  57
  58 static bool lowerIntrinsics(Module &M) {
  59   bool Changed = false;
  60   for (Function &F : M) {
  61     if (F.getName().startswith("llvm.load.relative."))
  62       Changed |= lowerLoadRelative(F);
  63   }
  64   return Changed;
  65 }
  66
  67 namespace {
  68
  69 class PreISelIntrinsicLoweringLegacyPass : public ModulePass {
  70 public:
  71   static char ID;
  72
  73   PreISelIntrinsicLoweringLegacyPass() : ModulePass(ID) {}
  74
  75   bool runOnModule(Module &M) override { return lowerIntrinsics(M); }
  76 };
  77
  78 } // end anonymous namespace
  79
  80 char PreISelIntrinsicLoweringLegacyPass::ID;
  81
  82 INITIALIZE_PASS(PreISelIntrinsicLoweringLegacyPass,
  83                 "pre-isel-intrinsic-lowering", "Pre-ISel Intrinsic Lowering",
  84                 false, false)
  85
  86 ModulePass *llvm::createPreISelIntrinsicLoweringPass() {
  87   return new PreISelIntrinsicLoweringLegacyPass;
  88 }
  89
  90 PreservedAnalyses PreISelIntrinsicLoweringPass::run(Module &M,
  91                                                     ModuleAnalysisManager &AM) {
  92   if (!lowerIntrinsics(M))
  93     return PreservedAnalyses::all();
  94   else
  95     return PreservedAnalyses::none();
  96 }