LowerGuardIntrinsic.cpp revision 360660 
1//===- LowerGuardIntrinsic.cpp - Lower the guard intrinsic ---------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass lowers the llvm.experimental.guard intrinsic to a conditional call
10// to @llvm.experimental.deoptimize.  Once this happens, the guard can no longer
11// be widened.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Transforms/Scalar/LowerGuardIntrinsic.h"
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/Analysis/GuardUtils.h"
18#include "llvm/IR/BasicBlock.h"
19#include "llvm/IR/Function.h"
20#include "llvm/IR/InstIterator.h"
21#include "llvm/IR/Instructions.h"
22#include "llvm/IR/Intrinsics.h"
23#include "llvm/IR/Module.h"
24#include "llvm/Pass.h"
25#include "llvm/Transforms/Scalar.h"
26#include "llvm/Transforms/Utils/GuardUtils.h"
27
28using namespace llvm;
29
30namespace {
31struct LowerGuardIntrinsicLegacyPass : public FunctionPass {
32  static char ID;
33  LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
34    initializeLowerGuardIntrinsicLegacyPassPass(
35        *PassRegistry::getPassRegistry());
36  }
37
38  bool runOnFunction(Function &F) override;
39};
40}
41
42static bool lowerGuardIntrinsic(Function &F) {
43  // Check if we can cheaply rule out the possibility of not having any work to
44  // do.
45  auto *GuardDecl = F.getParent()->getFunction(
46      Intrinsic::getName(Intrinsic::experimental_guard));
47  if (!GuardDecl || GuardDecl->use_empty())
48    return false;
49
50  SmallVector<CallInst *, 8> ToLower;
51  for (auto &I : instructions(F))
52    if (isGuard(&I))
53      ToLower.push_back(cast<CallInst>(&I));
54
55  if (ToLower.empty())
56    return false;
57
58  auto *DeoptIntrinsic = Intrinsic::getDeclaration(
59      F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()});
60  DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv());
61
62  for (auto *CI : ToLower) {
63    makeGuardControlFlowExplicit(DeoptIntrinsic, CI);
64    CI->eraseFromParent();
65  }
66
67  return true;
68}
69
70bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) {
71  return lowerGuardIntrinsic(F);
72}
73
74char LowerGuardIntrinsicLegacyPass::ID = 0;
75INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic",
76                "Lower the guard intrinsic to normal control flow", false,
77                false)
78
79Pass *llvm::createLowerGuardIntrinsicPass() {
80  return new LowerGuardIntrinsicLegacyPass();
81}
82
83PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
84                                               FunctionAnalysisManager &AM) {
85  if (lowerGuardIntrinsic(F))
86    return PreservedAnalyses::none();
87
88  return PreservedAnalyses::all();
89}
90