contrib/llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp

   1 //===- LowerGuardIntrinsic.cpp - Lower the guard intrinsic ---------------===//
   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 lowers the llvm.experimental.guard intrinsic to a conditional call
  11 // to @llvm.experimental.deoptimize.  Once this happens, the guard can no longer
  12 // be widened.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/Transforms/Scalar/LowerGuardIntrinsic.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/Analysis/GuardUtils.h"
  19 #include "llvm/IR/BasicBlock.h"
  20 #include "llvm/IR/Function.h"
  21 #include "llvm/IR/InstIterator.h"
  22 #include "llvm/IR/Instructions.h"
  23 #include "llvm/IR/Intrinsics.h"
  24 #include "llvm/IR/Module.h"
  25 #include "llvm/Pass.h"
  26 #include "llvm/Transforms/Scalar.h"
  27 #include "llvm/Transforms/Utils/GuardUtils.h"
  28
  29 using namespace llvm;
  30
  31 namespace {
  32 struct LowerGuardIntrinsicLegacyPass : public FunctionPass {
  33   static char ID;
  34   LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
  35     initializeLowerGuardIntrinsicLegacyPassPass(
  36         *PassRegistry::getPassRegistry());
  37   }
  38
  39   bool runOnFunction(Function &F) override;
  40 };
  41 }
  42
  43 static bool lowerGuardIntrinsic(Function &F) {
  44   // Check if we can cheaply rule out the possibility of not having any work to
  45   // do.
  46   auto *GuardDecl = F.getParent()->getFunction(
  47       Intrinsic::getName(Intrinsic::experimental_guard));
  48   if (!GuardDecl || GuardDecl->use_empty())
  49     return false;
  50
  51   SmallVector<CallInst *, 8> ToLower;
  52   for (auto &I : instructions(F))
  53     if (isGuard(&I))
  54       ToLower.push_back(cast<CallInst>(&I));
  55
  56   if (ToLower.empty())
  57     return false;
  58
  59   auto *DeoptIntrinsic = Intrinsic::getDeclaration(
  60       F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()});
  61   DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv());
  62
  63   for (auto *CI : ToLower) {
  64     makeGuardControlFlowExplicit(DeoptIntrinsic, CI);
  65     CI->eraseFromParent();
  66   }
  67
  68   return true;
  69 }
  70
  71 bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) {
  72   return lowerGuardIntrinsic(F);
  73 }
  74
  75 char LowerGuardIntrinsicLegacyPass::ID = 0;
  76 INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic",
  77                 "Lower the guard intrinsic to normal control flow", false,
  78                 false)
  79
  80 Pass *llvm::createLowerGuardIntrinsicPass() {
  81   return new LowerGuardIntrinsicLegacyPass();
  82 }
  83
  84 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
  85                                                FunctionAnalysisManager &AM) {
  86   if (lowerGuardIntrinsic(F))
  87     return PreservedAnalyses::none();
  88
  89   return PreservedAnalyses::all();
  90 }