LowerGuardIntrinsic.cpp revision 360784 
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/InitializePasses.h"
25#include "llvm/Pass.h"
26#include "llvm/Transforms/Scalar.h"
27#include "llvm/Transforms/Utils/GuardUtils.h"
28
29using namespace llvm;
30
31namespace {
32struct LowerGuardIntrinsicLegacyPass : public FunctionPass {
33  static char ID;
34  LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
35    initializeLowerGuardIntrinsicLegacyPassPass(
36        *PassRegistry::getPassRegistry());
37  }
38
39  bool runOnFunction(Function &F) override;
40};
41}
42
43static bool lowerGuardIntrinsic(Function &F) {
44  // Check if we can cheaply rule out the possibility of not having any work to
45  // do.
46  auto *GuardDecl = F.getParent()->getFunction(
47      Intrinsic::getName(Intrinsic::experimental_guard));
48  if (!GuardDecl || GuardDecl->use_empty())
49    return false;
50
51  SmallVector<CallInst *, 8> ToLower;
52  for (auto &I : instructions(F))
53    if (isGuard(&I))
54      ToLower.push_back(cast<CallInst>(&I));
55
56  if (ToLower.empty())
57    return false;
58
59  auto *DeoptIntrinsic = Intrinsic::getDeclaration(
60      F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()});
61  DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv());
62
63  for (auto *CI : ToLower) {
64    makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false);
65    CI->eraseFromParent();
66  }
67
68  return true;
69}
70
71bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) {
72  return lowerGuardIntrinsic(F);
73}
74
75char LowerGuardIntrinsicLegacyPass::ID = 0;
76INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic",
77                "Lower the guard intrinsic to normal control flow", false,
78                false)
79
80Pass *llvm::createLowerGuardIntrinsicPass() {
81  return new LowerGuardIntrinsicLegacyPass();
82}
83
84PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
85                                               FunctionAnalysisManager &AM) {
86  if (lowerGuardIntrinsic(F))
87    return PreservedAnalyses::none();
88
89  return PreservedAnalyses::all();
90}
91