llvm/llvm/lib/Transforms/Scalar/MakeGuardsExplicit.cpp

//===- MakeGuardsExplicit.cpp - Turn guard intrinsics into guard branches -===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass lowers the @llvm.experimental.guard intrinsic to the new form of
// guard represented as widenable explicit branch to the deopt block. The
// difference between this pass and LowerGuardIntrinsic is that after this pass
// the guard represented as intrinsic:
//
//   call void(i1, ...) @llvm.experimental.guard(i1 %old_cond) [ "deopt"() ]
//
// transforms to a guard represented as widenable explicit branch:
//
//   %widenable_cond = call i1 @llvm.experimental.widenable.condition()
//   br i1 (%old_cond & %widenable_cond), label %guarded, label %deopt
//
// Here:
//   - The semantics of @llvm.experimental.widenable.condition allows to replace
//     %widenable_cond with the construction (%widenable_cond & %any_other_cond)
//     without loss of correctness;
//   - %guarded is the lower part of old guard intrinsic's parent block split by
//     the intrinsic call;
//   - %deopt is a block containing a sole call to @llvm.experimental.deoptimize
//     intrinsic.
//
// Therefore, this branch preserves the property of widenability.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Scalar/MakeGuardsExplicit.h"
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/GuardUtils.h"

usingnamespacellvm;

static void turnToExplicitForm(CallInst *Guard, Function *DeoptIntrinsic) { … }

static bool explicifyGuards(Function &F) { … }

PreservedAnalyses MakeGuardsExplicitPass::run(Function &F,
                                           FunctionAnalysisManager &) { … }