65 lines
2.4 KiB
C++
65 lines
2.4 KiB
C++
//===-- GuardUtils.cpp - Utils for work with guards -------------*- C++ -*-===//
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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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// Utils that are used to perform transformations related to guards and their
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// conditions.
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/GuardUtils.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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using namespace llvm;
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static cl::opt<uint32_t> PredicatePassBranchWeight(
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"guards-predicate-pass-branch-weight", cl::Hidden, cl::init(1 << 20),
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cl::desc("The probability of a guard failing is assumed to be the "
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"reciprocal of this value (default = 1 << 20)"));
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void llvm::makeGuardControlFlowExplicit(Function *DeoptIntrinsic,
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CallInst *Guard) {
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OperandBundleDef DeoptOB(*Guard->getOperandBundle(LLVMContext::OB_deopt));
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SmallVector<Value *, 4> Args(std::next(Guard->arg_begin()), Guard->arg_end());
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auto *CheckBB = Guard->getParent();
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auto *DeoptBlockTerm =
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SplitBlockAndInsertIfThen(Guard->getArgOperand(0), Guard, 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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if (auto *MD = Guard->getMetadata(LLVMContext::MD_make_implicit))
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CheckBI->setMetadata(LLVMContext::MD_make_implicit, MD);
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MDBuilder MDB(Guard->getContext());
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CheckBI->setMetadata(LLVMContext::MD_prof,
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MDB.createBranchWeights(PredicatePassBranchWeight, 1));
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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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DeoptCall->setCallingConv(Guard->getCallingConv());
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DeoptBlockTerm->eraseFromParent();
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}
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