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
29 using namespace llvm;
30
31 namespace {
32 struct LowerGuardIntrinsicLegacyPass : public FunctionPass {
33 static char ID;
LowerGuardIntrinsicLegacyPass__anon6f5cbc8a0111::LowerGuardIntrinsicLegacyPass34 LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
35 initializeLowerGuardIntrinsicLegacyPassPass(
36 *PassRegistry::getPassRegistry());
37 }
38
39 bool runOnFunction(Function &F) override;
40 };
41 }
42
lowerGuardIntrinsic(Function & F)43 static 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
runOnFunction(Function & F)71 bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) {
72 return lowerGuardIntrinsic(F);
73 }
74
75 char LowerGuardIntrinsicLegacyPass::ID = 0;
76 INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic",
77 "Lower the guard intrinsic to normal control flow", false,
78 false)
79
createLowerGuardIntrinsicPass()80 Pass *llvm::createLowerGuardIntrinsicPass() {
81 return new LowerGuardIntrinsicLegacyPass();
82 }
83
run(Function & F,FunctionAnalysisManager & AM)84 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
85 FunctionAnalysisManager &AM) {
86 if (lowerGuardIntrinsic(F))
87 return PreservedAnalyses::none();
88
89 return PreservedAnalyses::all();
90 }
91