109 lines
3.4 KiB
C++
109 lines
3.4 KiB
C++
//===- LowerGuardIntrinsic.cpp - Lower the guard intrinsic ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass lowers the llvm.experimental.guard intrinsic to a conditional call
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// to @llvm.experimental.deoptimize. Once this happens, the guard can no longer
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// be widened.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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using namespace llvm;
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namespace {
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struct LowerGuardIntrinsic : public FunctionPass {
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static char ID;
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LowerGuardIntrinsic() : FunctionPass(ID) {
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initializeLowerGuardIntrinsicPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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};
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}
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static void MakeGuardControlFlowExplicit(Function *DeoptIntrinsic,
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CallInst *CI) {
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OperandBundleDef DeoptOB(*CI->getOperandBundle(LLVMContext::OB_deopt));
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SmallVector<Value *, 4> Args(std::next(CI->arg_begin()), CI->arg_end());
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auto *CheckBB = CI->getParent();
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auto *DeoptBlockTerm =
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SplitBlockAndInsertIfThen(CI->getArgOperand(0), CI, true);
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auto *CheckBI = cast<BranchInst>(CheckBB->getTerminator());
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// SplitBlockAndInsertIfThen inserts control flow that branches to
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// DeoptBlockTerm if the condition is true. We want the opposite.
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CheckBI->swapSuccessors();
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CheckBI->getSuccessor(0)->setName("guarded");
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CheckBI->getSuccessor(1)->setName("deopt");
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IRBuilder<> B(DeoptBlockTerm);
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auto *DeoptCall = B.CreateCall(DeoptIntrinsic, Args, {DeoptOB}, "");
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if (DeoptIntrinsic->getReturnType()->isVoidTy()) {
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B.CreateRetVoid();
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} else {
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DeoptCall->setName("deoptcall");
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B.CreateRet(DeoptCall);
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}
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DeoptBlockTerm->eraseFromParent();
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}
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bool LowerGuardIntrinsic::runOnFunction(Function &F) {
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// Check if we can cheaply rule out the possibility of not having any work to
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// do.
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auto *GuardDecl = F.getParent()->getFunction(
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Intrinsic::getName(Intrinsic::experimental_guard));
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if (!GuardDecl || GuardDecl->use_empty())
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return false;
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SmallVector<CallInst *, 8> ToLower;
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for (auto &I : instructions(F))
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if (auto *CI = dyn_cast<CallInst>(&I))
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if (auto *F = CI->getCalledFunction())
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if (F->getIntrinsicID() == Intrinsic::experimental_guard)
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ToLower.push_back(CI);
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if (ToLower.empty())
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return false;
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auto *DeoptIntrinsic = Intrinsic::getDeclaration(
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F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()});
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for (auto *CI : ToLower) {
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MakeGuardControlFlowExplicit(DeoptIntrinsic, CI);
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CI->eraseFromParent();
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}
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return true;
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}
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char LowerGuardIntrinsic::ID = 0;
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INITIALIZE_PASS(LowerGuardIntrinsic, "lower-guard-intrinsic",
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"Lower the guard intrinsic to normal control flow", false,
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false)
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Pass *llvm::createLowerGuardIntrinsicPass() {
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return new LowerGuardIntrinsic();
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}
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