5b4015e559
Replace BranchInst with CondBrInst/UncondBrInst/Instruction in headers
and handle the related fall out.
The removed code in simplifyUncondBranch was made dead in
0895b836d7, where FoldBranchToCommonDest
was changed to only handle conditional branches.
126 lines
4.8 KiB
C++
126 lines
4.8 KiB
C++
//===-- GuardUtils.cpp - Utils for work with guards -------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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/Analysis/GuardUtils.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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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, bool UseWC) {
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OperandBundleDef DeoptOB(*Guard->getOperandBundle(LLVMContext::OB_deopt));
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SmallVector<Value *, 4> Args(drop_begin(Guard->args()));
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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<CondBrInst>(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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if (UseWC) {
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// We want the guard to be expressed as explicit control flow, but still be
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// widenable. For that, we add Widenable Condition intrinsic call to the
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// guard's condition.
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IRBuilder<> B(CheckBI);
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auto *WC = B.CreateIntrinsic(Intrinsic::experimental_widenable_condition,
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{}, nullptr, "widenable_cond");
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CheckBI->setCondition(B.CreateAnd(CheckBI->getCondition(), WC,
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"exiplicit_guard_cond"));
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assert(isWidenableBranch(CheckBI) && "Branch must be widenable.");
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}
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}
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void llvm::widenWidenableBranch(CondBrInst *WidenableBR, Value *NewCond) {
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assert(isWidenableBranch(WidenableBR) && "precondition");
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// The tempting trivially option is to produce something like this:
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// br (and oldcond, newcond) where oldcond is assumed to contain a widenable
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// condition, but that doesn't match the pattern parseWidenableBranch expects
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// so we have to be more sophisticated.
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Use *C, *WC;
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BasicBlock *IfTrueBB, *IfFalseBB;
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parseWidenableBranch(WidenableBR, C, WC, IfTrueBB, IfFalseBB);
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if (!C) {
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// br (wc()), ... form
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IRBuilder<> B(WidenableBR);
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WidenableBR->setCondition(B.CreateAnd(NewCond, WC->get()));
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} else {
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// br (wc & C), ... form
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IRBuilder<> B(WidenableBR);
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C->set(B.CreateAnd(NewCond, C->get()));
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Instruction *WCAnd = cast<Instruction>(WidenableBR->getCondition());
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// Condition is only guaranteed to dominate branch
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WCAnd->moveBefore(WidenableBR->getIterator());
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}
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assert(isWidenableBranch(WidenableBR) && "preserve widenabiliy");
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}
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void llvm::setWidenableBranchCond(CondBrInst *WidenableBR, Value *NewCond) {
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assert(isWidenableBranch(WidenableBR) && "precondition");
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Use *C, *WC;
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BasicBlock *IfTrueBB, *IfFalseBB;
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parseWidenableBranch(WidenableBR, C, WC, IfTrueBB, IfFalseBB);
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if (!C) {
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// br (wc()), ... form
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IRBuilder<> B(WidenableBR);
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WidenableBR->setCondition(B.CreateAnd(NewCond, WC->get()));
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} else {
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// br (wc & C), ... form
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Instruction *WCAnd = cast<Instruction>(WidenableBR->getCondition());
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// Condition is only guaranteed to dominate branch
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WCAnd->moveBefore(WidenableBR->getIterator());
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C->set(NewCond);
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}
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assert(isWidenableBranch(WidenableBR) && "preserve widenabiliy");
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}
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