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/Passes.h"
15 #include "llvm/IR/Function.h"
16 #include "llvm/IR/IRBuilder.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/Intrinsics.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Pass.h"
21 
22 using namespace llvm;
23 
24 namespace {
25 
26 bool lowerLoadRelative(Function &F) {
27   if (F.use_empty())
28     return false;
29 
30   bool Changed = false;
31   Type *Int32Ty = Type::getInt32Ty(F.getContext());
32   Type *Int32PtrTy = Int32Ty->getPointerTo();
33   Type *Int8Ty = Type::getInt8Ty(F.getContext());
34 
35   for (auto I = F.use_begin(), E = F.use_end(); I != E;) {
36     auto CI = dyn_cast<CallInst>(I->getUser());
37     ++I;
38     if (!CI || CI->getCalledValue() != &F)
39       continue;
40 
41     IRBuilder<> B(CI);
42     Value *OffsetPtr =
43         B.CreateGEP(Int8Ty, CI->getArgOperand(0), CI->getArgOperand(1));
44     Value *OffsetPtrI32 = B.CreateBitCast(OffsetPtr, Int32PtrTy);
45     Value *OffsetI32 = B.CreateAlignedLoad(OffsetPtrI32, 4);
46 
47     Value *ResultPtr = B.CreateGEP(Int8Ty, CI->getArgOperand(0), OffsetI32);
48 
49     CI->replaceAllUsesWith(ResultPtr);
50     CI->eraseFromParent();
51     Changed = true;
52   }
53 
54   return Changed;
55 }
56 
57 bool lowerIntrinsics(Module &M) {
58   bool Changed = false;
59   for (Function &F : M) {
60     if (F.getName().startswith("llvm.load.relative."))
61       Changed |= lowerLoadRelative(F);
62   }
63   return Changed;
64 }
65 
66 class PreISelIntrinsicLowering : public ModulePass {
67 public:
68   static char ID;
69   PreISelIntrinsicLowering() : ModulePass(ID) {}
70 
71   bool runOnModule(Module &M) {
72     return lowerIntrinsics(M);
73   }
74 };
75 
76 char PreISelIntrinsicLowering::ID;
77 
78 }
79 
80 INITIALIZE_PASS(PreISelIntrinsicLowering, "pre-isel-intrinsic-lowering",
81                 "Pre-ISel Intrinsic Lowering", false, false)
82 
83 ModulePass *llvm::createPreISelIntrinsicLoweringPass() {
84   return new PreISelIntrinsicLowering;
85 }
86