xref: /freebsd/contrib/llvm-project/llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp (revision 9e5787d2284e187abb5b654d924394a65772e004)
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;
34   LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
35     initializeLowerGuardIntrinsicLegacyPassPass(
36         *PassRegistry::getPassRegistry());
37   }
38 
39   bool runOnFunction(Function &F) override;
40 };
41 }
42 
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 
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 
80 Pass *llvm::createLowerGuardIntrinsicPass() {
81   return new LowerGuardIntrinsicLegacyPass();
82 }
83 
84 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
85                                                FunctionAnalysisManager &AM) {
86   if (lowerGuardIntrinsic(F))
87     return PreservedAnalyses::none();
88 
89   return PreservedAnalyses::all();
90 }
91