forked from OSchip/llvm-project
117 lines
3.8 KiB
C++
117 lines
3.8 KiB
C++
//===- EscapeEnumerator.cpp -----------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Defines a helper class that enumerates all possible exits from a function,
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// including exception handling.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/EscapeEnumerator.h"
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#include "llvm/ADT/Triple.h"
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#include "llvm/Analysis/EHPersonalities.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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static FunctionCallee getDefaultPersonalityFn(Module *M) {
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LLVMContext &C = M->getContext();
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Triple T(M->getTargetTriple());
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EHPersonality Pers = getDefaultEHPersonality(T);
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return M->getOrInsertFunction(getEHPersonalityName(Pers),
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FunctionType::get(Type::getInt32Ty(C), true));
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}
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IRBuilder<> *EscapeEnumerator::Next() {
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if (Done)
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return nullptr;
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// Find all 'return', 'resume', and 'unwind' instructions.
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while (StateBB != StateE) {
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BasicBlock *CurBB = &*StateBB++;
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// Branches and invokes do not escape, only unwind, resume, and return
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// do.
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Instruction *TI = CurBB->getTerminator();
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if (!isa<ReturnInst>(TI) && !isa<ResumeInst>(TI))
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continue;
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// If the ret instruction is followed by a musttaill call,
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// or a bitcast instruction and then a musttail call, we should return
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// the musttail call as the insertion point to not break the musttail
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// contract.
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auto AdjustMustTailCall = [&](Instruction *I) -> Instruction * {
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auto *RI = dyn_cast<ReturnInst>(I);
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if (!RI || !RI->getPrevNode())
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return I;
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auto *CI = dyn_cast<CallInst>(RI->getPrevNode());
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if (CI && CI->isMustTailCall())
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return CI;
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auto *BI = dyn_cast<BitCastInst>(RI->getPrevNode());
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if (!BI || !BI->getPrevNode())
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return I;
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CI = dyn_cast<CallInst>(BI->getPrevNode());
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if (CI && CI->isMustTailCall())
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return CI;
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return I;
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};
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Builder.SetInsertPoint(AdjustMustTailCall(TI));
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return &Builder;
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}
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Done = true;
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if (!HandleExceptions)
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return nullptr;
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if (F.doesNotThrow())
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return nullptr;
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// Find all 'call' instructions that may throw.
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// We cannot tranform calls with musttail tag.
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SmallVector<Instruction *, 16> Calls;
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for (BasicBlock &BB : F)
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for (Instruction &II : BB)
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if (CallInst *CI = dyn_cast<CallInst>(&II))
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if (!CI->doesNotThrow() && !CI->isMustTailCall())
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Calls.push_back(CI);
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if (Calls.empty())
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return nullptr;
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// Create a cleanup block.
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LLVMContext &C = F.getContext();
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BasicBlock *CleanupBB = BasicBlock::Create(C, CleanupBBName, &F);
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Type *ExnTy = StructType::get(Type::getInt8PtrTy(C), Type::getInt32Ty(C));
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if (!F.hasPersonalityFn()) {
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FunctionCallee PersFn = getDefaultPersonalityFn(F.getParent());
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F.setPersonalityFn(cast<Constant>(PersFn.getCallee()));
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}
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if (isScopedEHPersonality(classifyEHPersonality(F.getPersonalityFn()))) {
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report_fatal_error("Scoped EH not supported");
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}
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LandingPadInst *LPad =
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LandingPadInst::Create(ExnTy, 1, "cleanup.lpad", CleanupBB);
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LPad->setCleanup(true);
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ResumeInst *RI = ResumeInst::Create(LPad, CleanupBB);
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// Transform the 'call' instructions into 'invoke's branching to the
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// cleanup block. Go in reverse order to make prettier BB names.
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SmallVector<Value *, 16> Args;
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for (unsigned I = Calls.size(); I != 0;) {
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CallInst *CI = cast<CallInst>(Calls[--I]);
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changeToInvokeAndSplitBasicBlock(CI, CleanupBB);
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}
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Builder.SetInsertPoint(RI);
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return &Builder;
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}
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