1144 lines
42 KiB
C++
1144 lines
42 KiB
C++
//===--- CGCleanup.cpp - Bookkeeping and code emission for cleanups -------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains code dealing with the IR generation for cleanups
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// and related information.
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//
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// A "cleanup" is a piece of code which needs to be executed whenever
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// control transfers out of a particular scope. This can be
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// conditionalized to occur only on exceptional control flow, only on
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// normal control flow, or both.
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//
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//===----------------------------------------------------------------------===//
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#include "CGCleanup.h"
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#include "CodeGenFunction.h"
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using namespace clang;
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using namespace CodeGen;
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bool DominatingValue<RValue>::saved_type::needsSaving(RValue rv) {
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if (rv.isScalar())
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return DominatingLLVMValue::needsSaving(rv.getScalarVal());
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if (rv.isAggregate())
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return DominatingLLVMValue::needsSaving(rv.getAggregateAddr());
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return true;
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}
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DominatingValue<RValue>::saved_type
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DominatingValue<RValue>::saved_type::save(CodeGenFunction &CGF, RValue rv) {
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if (rv.isScalar()) {
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llvm::Value *V = rv.getScalarVal();
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// These automatically dominate and don't need to be saved.
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if (!DominatingLLVMValue::needsSaving(V))
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return saved_type(V, ScalarLiteral);
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// Everything else needs an alloca.
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llvm::Value *addr = CGF.CreateTempAlloca(V->getType(), "saved-rvalue");
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CGF.Builder.CreateStore(V, addr);
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return saved_type(addr, ScalarAddress);
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}
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if (rv.isComplex()) {
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CodeGenFunction::ComplexPairTy V = rv.getComplexVal();
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llvm::Type *ComplexTy =
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llvm::StructType::get(V.first->getType(), V.second->getType(),
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(void*) 0);
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llvm::Value *addr = CGF.CreateTempAlloca(ComplexTy, "saved-complex");
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CGF.Builder.CreateStore(V.first, CGF.Builder.CreateStructGEP(addr, 0));
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CGF.Builder.CreateStore(V.second, CGF.Builder.CreateStructGEP(addr, 1));
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return saved_type(addr, ComplexAddress);
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}
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assert(rv.isAggregate());
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llvm::Value *V = rv.getAggregateAddr(); // TODO: volatile?
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if (!DominatingLLVMValue::needsSaving(V))
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return saved_type(V, AggregateLiteral);
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llvm::Value *addr = CGF.CreateTempAlloca(V->getType(), "saved-rvalue");
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CGF.Builder.CreateStore(V, addr);
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return saved_type(addr, AggregateAddress);
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}
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/// Given a saved r-value produced by SaveRValue, perform the code
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/// necessary to restore it to usability at the current insertion
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/// point.
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RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) {
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switch (K) {
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case ScalarLiteral:
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return RValue::get(Value);
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case ScalarAddress:
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return RValue::get(CGF.Builder.CreateLoad(Value));
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case AggregateLiteral:
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return RValue::getAggregate(Value);
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case AggregateAddress:
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return RValue::getAggregate(CGF.Builder.CreateLoad(Value));
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case ComplexAddress: {
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llvm::Value *real =
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CGF.Builder.CreateLoad(CGF.Builder.CreateStructGEP(Value, 0));
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llvm::Value *imag =
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CGF.Builder.CreateLoad(CGF.Builder.CreateStructGEP(Value, 1));
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return RValue::getComplex(real, imag);
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}
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}
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llvm_unreachable("bad saved r-value kind");
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}
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/// Push an entry of the given size onto this protected-scope stack.
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char *EHScopeStack::allocate(size_t Size) {
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if (!StartOfBuffer) {
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unsigned Capacity = 1024;
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while (Capacity < Size) Capacity *= 2;
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StartOfBuffer = new char[Capacity];
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StartOfData = EndOfBuffer = StartOfBuffer + Capacity;
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} else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {
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unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;
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unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);
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unsigned NewCapacity = CurrentCapacity;
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do {
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NewCapacity *= 2;
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} while (NewCapacity < UsedCapacity + Size);
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char *NewStartOfBuffer = new char[NewCapacity];
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char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity;
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char *NewStartOfData = NewEndOfBuffer - UsedCapacity;
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memcpy(NewStartOfData, StartOfData, UsedCapacity);
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delete [] StartOfBuffer;
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StartOfBuffer = NewStartOfBuffer;
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EndOfBuffer = NewEndOfBuffer;
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StartOfData = NewStartOfData;
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}
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assert(StartOfBuffer + Size <= StartOfData);
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StartOfData -= Size;
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return StartOfData;
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}
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EHScopeStack::stable_iterator
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EHScopeStack::getInnermostActiveNormalCleanup() const {
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for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end();
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si != se; ) {
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EHCleanupScope &cleanup = cast<EHCleanupScope>(*find(si));
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if (cleanup.isActive()) return si;
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si = cleanup.getEnclosingNormalCleanup();
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}
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return stable_end();
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}
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EHScopeStack::stable_iterator EHScopeStack::getInnermostActiveEHScope() const {
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for (stable_iterator si = getInnermostEHScope(), se = stable_end();
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si != se; ) {
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// Skip over inactive cleanups.
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EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*find(si));
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if (cleanup && !cleanup->isActive()) {
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si = cleanup->getEnclosingEHScope();
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continue;
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}
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// All other scopes are always active.
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return si;
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}
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return stable_end();
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}
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void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
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assert(((Size % sizeof(void*)) == 0) && "cleanup type is misaligned");
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char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));
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bool IsNormalCleanup = Kind & NormalCleanup;
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bool IsEHCleanup = Kind & EHCleanup;
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bool IsActive = !(Kind & InactiveCleanup);
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EHCleanupScope *Scope =
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new (Buffer) EHCleanupScope(IsNormalCleanup,
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IsEHCleanup,
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IsActive,
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Size,
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BranchFixups.size(),
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InnermostNormalCleanup,
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InnermostEHScope);
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if (IsNormalCleanup)
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InnermostNormalCleanup = stable_begin();
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if (IsEHCleanup)
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InnermostEHScope = stable_begin();
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return Scope->getCleanupBuffer();
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}
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void EHScopeStack::popCleanup() {
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assert(!empty() && "popping exception stack when not empty");
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assert(isa<EHCleanupScope>(*begin()));
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EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin());
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InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();
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InnermostEHScope = Cleanup.getEnclosingEHScope();
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StartOfData += Cleanup.getAllocatedSize();
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// Destroy the cleanup.
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Cleanup.~EHCleanupScope();
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// Check whether we can shrink the branch-fixups stack.
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if (!BranchFixups.empty()) {
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// If we no longer have any normal cleanups, all the fixups are
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// complete.
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if (!hasNormalCleanups())
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BranchFixups.clear();
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// Otherwise we can still trim out unnecessary nulls.
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else
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popNullFixups();
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}
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}
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EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) {
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assert(getInnermostEHScope() == stable_end());
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char *buffer = allocate(EHFilterScope::getSizeForNumFilters(numFilters));
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EHFilterScope *filter = new (buffer) EHFilterScope(numFilters);
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InnermostEHScope = stable_begin();
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return filter;
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}
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void EHScopeStack::popFilter() {
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assert(!empty() && "popping exception stack when not empty");
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EHFilterScope &filter = cast<EHFilterScope>(*begin());
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StartOfData += EHFilterScope::getSizeForNumFilters(filter.getNumFilters());
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InnermostEHScope = filter.getEnclosingEHScope();
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}
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EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) {
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char *buffer = allocate(EHCatchScope::getSizeForNumHandlers(numHandlers));
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EHCatchScope *scope =
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new (buffer) EHCatchScope(numHandlers, InnermostEHScope);
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InnermostEHScope = stable_begin();
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return scope;
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}
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void EHScopeStack::pushTerminate() {
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char *Buffer = allocate(EHTerminateScope::getSize());
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new (Buffer) EHTerminateScope(InnermostEHScope);
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InnermostEHScope = stable_begin();
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}
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/// Remove any 'null' fixups on the stack. However, we can't pop more
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/// fixups than the fixup depth on the innermost normal cleanup, or
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/// else fixups that we try to add to that cleanup will end up in the
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/// wrong place. We *could* try to shrink fixup depths, but that's
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/// actually a lot of work for little benefit.
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void EHScopeStack::popNullFixups() {
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// We expect this to only be called when there's still an innermost
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// normal cleanup; otherwise there really shouldn't be any fixups.
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assert(hasNormalCleanups());
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EHScopeStack::iterator it = find(InnermostNormalCleanup);
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unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth();
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assert(BranchFixups.size() >= MinSize && "fixup stack out of order");
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while (BranchFixups.size() > MinSize &&
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BranchFixups.back().Destination == 0)
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BranchFixups.pop_back();
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}
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void CodeGenFunction::initFullExprCleanup() {
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// Create a variable to decide whether the cleanup needs to be run.
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llvm::AllocaInst *active
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= CreateTempAlloca(Builder.getInt1Ty(), "cleanup.cond");
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// Initialize it to false at a site that's guaranteed to be run
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// before each evaluation.
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setBeforeOutermostConditional(Builder.getFalse(), active);
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// Initialize it to true at the current location.
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Builder.CreateStore(Builder.getTrue(), active);
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// Set that as the active flag in the cleanup.
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EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin());
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assert(cleanup.getActiveFlag() == 0 && "cleanup already has active flag?");
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cleanup.setActiveFlag(active);
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if (cleanup.isNormalCleanup()) cleanup.setTestFlagInNormalCleanup();
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if (cleanup.isEHCleanup()) cleanup.setTestFlagInEHCleanup();
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}
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void EHScopeStack::Cleanup::anchor() {}
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/// All the branch fixups on the EH stack have propagated out past the
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/// outermost normal cleanup; resolve them all by adding cases to the
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/// given switch instruction.
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static void ResolveAllBranchFixups(CodeGenFunction &CGF,
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llvm::SwitchInst *Switch,
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llvm::BasicBlock *CleanupEntry) {
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llvm::SmallPtrSet<llvm::BasicBlock*, 4> CasesAdded;
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for (unsigned I = 0, E = CGF.EHStack.getNumBranchFixups(); I != E; ++I) {
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// Skip this fixup if its destination isn't set.
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BranchFixup &Fixup = CGF.EHStack.getBranchFixup(I);
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if (Fixup.Destination == 0) continue;
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// If there isn't an OptimisticBranchBlock, then InitialBranch is
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// still pointing directly to its destination; forward it to the
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// appropriate cleanup entry. This is required in the specific
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// case of
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// { std::string s; goto lbl; }
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// lbl:
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// i.e. where there's an unresolved fixup inside a single cleanup
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// entry which we're currently popping.
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if (Fixup.OptimisticBranchBlock == 0) {
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new llvm::StoreInst(CGF.Builder.getInt32(Fixup.DestinationIndex),
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CGF.getNormalCleanupDestSlot(),
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Fixup.InitialBranch);
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Fixup.InitialBranch->setSuccessor(0, CleanupEntry);
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}
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// Don't add this case to the switch statement twice.
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if (!CasesAdded.insert(Fixup.Destination)) continue;
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Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex),
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Fixup.Destination);
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}
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CGF.EHStack.clearFixups();
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}
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/// Transitions the terminator of the given exit-block of a cleanup to
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/// be a cleanup switch.
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static llvm::SwitchInst *TransitionToCleanupSwitch(CodeGenFunction &CGF,
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llvm::BasicBlock *Block) {
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// If it's a branch, turn it into a switch whose default
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// destination is its original target.
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llvm::TerminatorInst *Term = Block->getTerminator();
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assert(Term && "can't transition block without terminator");
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if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
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assert(Br->isUnconditional());
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llvm::LoadInst *Load =
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new llvm::LoadInst(CGF.getNormalCleanupDestSlot(), "cleanup.dest", Term);
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llvm::SwitchInst *Switch =
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llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block);
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Br->eraseFromParent();
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return Switch;
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} else {
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return cast<llvm::SwitchInst>(Term);
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}
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}
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void CodeGenFunction::ResolveBranchFixups(llvm::BasicBlock *Block) {
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assert(Block && "resolving a null target block");
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if (!EHStack.getNumBranchFixups()) return;
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assert(EHStack.hasNormalCleanups() &&
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"branch fixups exist with no normal cleanups on stack");
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llvm::SmallPtrSet<llvm::BasicBlock*, 4> ModifiedOptimisticBlocks;
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bool ResolvedAny = false;
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for (unsigned I = 0, E = EHStack.getNumBranchFixups(); I != E; ++I) {
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// Skip this fixup if its destination doesn't match.
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BranchFixup &Fixup = EHStack.getBranchFixup(I);
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if (Fixup.Destination != Block) continue;
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Fixup.Destination = 0;
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ResolvedAny = true;
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// If it doesn't have an optimistic branch block, LatestBranch is
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// already pointing to the right place.
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llvm::BasicBlock *BranchBB = Fixup.OptimisticBranchBlock;
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if (!BranchBB)
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continue;
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// Don't process the same optimistic branch block twice.
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if (!ModifiedOptimisticBlocks.insert(BranchBB))
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continue;
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llvm::SwitchInst *Switch = TransitionToCleanupSwitch(*this, BranchBB);
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// Add a case to the switch.
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Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block);
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}
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if (ResolvedAny)
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EHStack.popNullFixups();
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}
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/// Pops cleanup blocks until the given savepoint is reached.
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void CodeGenFunction::PopCleanupBlocks(EHScopeStack::stable_iterator Old) {
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assert(Old.isValid());
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while (EHStack.stable_begin() != Old) {
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EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
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// As long as Old strictly encloses the scope's enclosing normal
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// cleanup, we're going to emit another normal cleanup which
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// fallthrough can propagate through.
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bool FallThroughIsBranchThrough =
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Old.strictlyEncloses(Scope.getEnclosingNormalCleanup());
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PopCleanupBlock(FallThroughIsBranchThrough);
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}
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}
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/// Pops cleanup blocks until the given savepoint is reached, then add the
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/// cleanups from the given savepoint in the lifetime-extended cleanups stack.
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void
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CodeGenFunction::PopCleanupBlocks(EHScopeStack::stable_iterator Old,
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size_t OldLifetimeExtendedSize) {
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PopCleanupBlocks(Old);
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// Move our deferred cleanups onto the EH stack.
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for (size_t I = OldLifetimeExtendedSize,
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E = LifetimeExtendedCleanupStack.size(); I != E; /**/) {
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// Alignment should be guaranteed by the vptrs in the individual cleanups.
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assert((I % llvm::alignOf<LifetimeExtendedCleanupHeader>() == 0) &&
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"misaligned cleanup stack entry");
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LifetimeExtendedCleanupHeader &Header =
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reinterpret_cast<LifetimeExtendedCleanupHeader&>(
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LifetimeExtendedCleanupStack[I]);
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I += sizeof(Header);
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EHStack.pushCopyOfCleanup(Header.getKind(),
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&LifetimeExtendedCleanupStack[I],
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Header.getSize());
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I += Header.getSize();
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}
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LifetimeExtendedCleanupStack.resize(OldLifetimeExtendedSize);
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}
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static llvm::BasicBlock *CreateNormalEntry(CodeGenFunction &CGF,
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EHCleanupScope &Scope) {
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assert(Scope.isNormalCleanup());
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llvm::BasicBlock *Entry = Scope.getNormalBlock();
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if (!Entry) {
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Entry = CGF.createBasicBlock("cleanup");
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Scope.setNormalBlock(Entry);
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}
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return Entry;
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}
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/// Attempts to reduce a cleanup's entry block to a fallthrough. This
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/// is basically llvm::MergeBlockIntoPredecessor, except
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/// simplified/optimized for the tighter constraints on cleanup blocks.
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///
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/// Returns the new block, whatever it is.
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static llvm::BasicBlock *SimplifyCleanupEntry(CodeGenFunction &CGF,
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llvm::BasicBlock *Entry) {
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llvm::BasicBlock *Pred = Entry->getSinglePredecessor();
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if (!Pred) return Entry;
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llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator());
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if (!Br || Br->isConditional()) return Entry;
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assert(Br->getSuccessor(0) == Entry);
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// If we were previously inserting at the end of the cleanup entry
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// block, we'll need to continue inserting at the end of the
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// predecessor.
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bool WasInsertBlock = CGF.Builder.GetInsertBlock() == Entry;
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assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end());
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// Kill the branch.
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Br->eraseFromParent();
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// Replace all uses of the entry with the predecessor, in case there
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// are phis in the cleanup.
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Entry->replaceAllUsesWith(Pred);
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// Merge the blocks.
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Pred->getInstList().splice(Pred->end(), Entry->getInstList());
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// Kill the entry block.
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Entry->eraseFromParent();
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if (WasInsertBlock)
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CGF.Builder.SetInsertPoint(Pred);
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return Pred;
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}
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static void EmitCleanup(CodeGenFunction &CGF,
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EHScopeStack::Cleanup *Fn,
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EHScopeStack::Cleanup::Flags flags,
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llvm::Value *ActiveFlag) {
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// EH cleanups always occur within a terminate scope.
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if (flags.isForEHCleanup()) CGF.EHStack.pushTerminate();
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// If there's an active flag, load it and skip the cleanup if it's
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// false.
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llvm::BasicBlock *ContBB = 0;
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if (ActiveFlag) {
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ContBB = CGF.createBasicBlock("cleanup.done");
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llvm::BasicBlock *CleanupBB = CGF.createBasicBlock("cleanup.action");
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llvm::Value *IsActive
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= CGF.Builder.CreateLoad(ActiveFlag, "cleanup.is_active");
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CGF.Builder.CreateCondBr(IsActive, CleanupBB, ContBB);
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CGF.EmitBlock(CleanupBB);
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}
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// Ask the cleanup to emit itself.
|
|
Fn->Emit(CGF, flags);
|
|
assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?");
|
|
|
|
// Emit the continuation block if there was an active flag.
|
|
if (ActiveFlag)
|
|
CGF.EmitBlock(ContBB);
|
|
|
|
// Leave the terminate scope.
|
|
if (flags.isForEHCleanup()) CGF.EHStack.popTerminate();
|
|
}
|
|
|
|
static void ForwardPrebranchedFallthrough(llvm::BasicBlock *Exit,
|
|
llvm::BasicBlock *From,
|
|
llvm::BasicBlock *To) {
|
|
// Exit is the exit block of a cleanup, so it always terminates in
|
|
// an unconditional branch or a switch.
|
|
llvm::TerminatorInst *Term = Exit->getTerminator();
|
|
|
|
if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
|
|
assert(Br->isUnconditional() && Br->getSuccessor(0) == From);
|
|
Br->setSuccessor(0, To);
|
|
} else {
|
|
llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Term);
|
|
for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)
|
|
if (Switch->getSuccessor(I) == From)
|
|
Switch->setSuccessor(I, To);
|
|
}
|
|
}
|
|
|
|
/// We don't need a normal entry block for the given cleanup.
|
|
/// Optimistic fixup branches can cause these blocks to come into
|
|
/// existence anyway; if so, destroy it.
|
|
///
|
|
/// The validity of this transformation is very much specific to the
|
|
/// exact ways in which we form branches to cleanup entries.
|
|
static void destroyOptimisticNormalEntry(CodeGenFunction &CGF,
|
|
EHCleanupScope &scope) {
|
|
llvm::BasicBlock *entry = scope.getNormalBlock();
|
|
if (!entry) return;
|
|
|
|
// Replace all the uses with unreachable.
|
|
llvm::BasicBlock *unreachableBB = CGF.getUnreachableBlock();
|
|
for (llvm::BasicBlock::use_iterator
|
|
i = entry->use_begin(), e = entry->use_end(); i != e; ) {
|
|
llvm::Use &use = i.getUse();
|
|
++i;
|
|
|
|
use.set(unreachableBB);
|
|
|
|
// The only uses should be fixup switches.
|
|
llvm::SwitchInst *si = cast<llvm::SwitchInst>(use.getUser());
|
|
if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {
|
|
// Replace the switch with a branch.
|
|
llvm::BranchInst::Create(si->case_begin().getCaseSuccessor(), si);
|
|
|
|
// The switch operand is a load from the cleanup-dest alloca.
|
|
llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition());
|
|
|
|
// Destroy the switch.
|
|
si->eraseFromParent();
|
|
|
|
// Destroy the load.
|
|
assert(condition->getOperand(0) == CGF.NormalCleanupDest);
|
|
assert(condition->use_empty());
|
|
condition->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
assert(entry->use_empty());
|
|
delete entry;
|
|
}
|
|
|
|
/// Pops a cleanup block. If the block includes a normal cleanup, the
|
|
/// current insertion point is threaded through the cleanup, as are
|
|
/// any branch fixups on the cleanup.
|
|
void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough) {
|
|
assert(!EHStack.empty() && "cleanup stack is empty!");
|
|
assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!");
|
|
EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
|
|
assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());
|
|
|
|
// Remember activation information.
|
|
bool IsActive = Scope.isActive();
|
|
llvm::Value *NormalActiveFlag =
|
|
Scope.shouldTestFlagInNormalCleanup() ? Scope.getActiveFlag() : 0;
|
|
llvm::Value *EHActiveFlag =
|
|
Scope.shouldTestFlagInEHCleanup() ? Scope.getActiveFlag() : 0;
|
|
|
|
// Check whether we need an EH cleanup. This is only true if we've
|
|
// generated a lazy EH cleanup block.
|
|
llvm::BasicBlock *EHEntry = Scope.getCachedEHDispatchBlock();
|
|
assert(Scope.hasEHBranches() == (EHEntry != 0));
|
|
bool RequiresEHCleanup = (EHEntry != 0);
|
|
EHScopeStack::stable_iterator EHParent = Scope.getEnclosingEHScope();
|
|
|
|
// Check the three conditions which might require a normal cleanup:
|
|
|
|
// - whether there are branch fix-ups through this cleanup
|
|
unsigned FixupDepth = Scope.getFixupDepth();
|
|
bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth;
|
|
|
|
// - whether there are branch-throughs or branch-afters
|
|
bool HasExistingBranches = Scope.hasBranches();
|
|
|
|
// - whether there's a fallthrough
|
|
llvm::BasicBlock *FallthroughSource = Builder.GetInsertBlock();
|
|
bool HasFallthrough = (FallthroughSource != 0 && IsActive);
|
|
|
|
// Branch-through fall-throughs leave the insertion point set to the
|
|
// end of the last cleanup, which points to the current scope. The
|
|
// rest of IR gen doesn't need to worry about this; it only happens
|
|
// during the execution of PopCleanupBlocks().
|
|
bool HasPrebranchedFallthrough =
|
|
(FallthroughSource && FallthroughSource->getTerminator());
|
|
|
|
// If this is a normal cleanup, then having a prebranched
|
|
// fallthrough implies that the fallthrough source unconditionally
|
|
// jumps here.
|
|
assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough ||
|
|
(Scope.getNormalBlock() &&
|
|
FallthroughSource->getTerminator()->getSuccessor(0)
|
|
== Scope.getNormalBlock()));
|
|
|
|
bool RequiresNormalCleanup = false;
|
|
if (Scope.isNormalCleanup() &&
|
|
(HasFixups || HasExistingBranches || HasFallthrough)) {
|
|
RequiresNormalCleanup = true;
|
|
}
|
|
|
|
// If we have a prebranched fallthrough into an inactive normal
|
|
// cleanup, rewrite it so that it leads to the appropriate place.
|
|
if (Scope.isNormalCleanup() && HasPrebranchedFallthrough && !IsActive) {
|
|
llvm::BasicBlock *prebranchDest;
|
|
|
|
// If the prebranch is semantically branching through the next
|
|
// cleanup, just forward it to the next block, leaving the
|
|
// insertion point in the prebranched block.
|
|
if (FallthroughIsBranchThrough) {
|
|
EHScope &enclosing = *EHStack.find(Scope.getEnclosingNormalCleanup());
|
|
prebranchDest = CreateNormalEntry(*this, cast<EHCleanupScope>(enclosing));
|
|
|
|
// Otherwise, we need to make a new block. If the normal cleanup
|
|
// isn't being used at all, we could actually reuse the normal
|
|
// entry block, but this is simpler, and it avoids conflicts with
|
|
// dead optimistic fixup branches.
|
|
} else {
|
|
prebranchDest = createBasicBlock("forwarded-prebranch");
|
|
EmitBlock(prebranchDest);
|
|
}
|
|
|
|
llvm::BasicBlock *normalEntry = Scope.getNormalBlock();
|
|
assert(normalEntry && !normalEntry->use_empty());
|
|
|
|
ForwardPrebranchedFallthrough(FallthroughSource,
|
|
normalEntry, prebranchDest);
|
|
}
|
|
|
|
// If we don't need the cleanup at all, we're done.
|
|
if (!RequiresNormalCleanup && !RequiresEHCleanup) {
|
|
destroyOptimisticNormalEntry(*this, Scope);
|
|
EHStack.popCleanup(); // safe because there are no fixups
|
|
assert(EHStack.getNumBranchFixups() == 0 ||
|
|
EHStack.hasNormalCleanups());
|
|
return;
|
|
}
|
|
|
|
// Copy the cleanup emission data out. Note that SmallVector
|
|
// guarantees maximal alignment for its buffer regardless of its
|
|
// type parameter.
|
|
SmallVector<char, 8*sizeof(void*)> CleanupBuffer;
|
|
CleanupBuffer.reserve(Scope.getCleanupSize());
|
|
memcpy(CleanupBuffer.data(),
|
|
Scope.getCleanupBuffer(), Scope.getCleanupSize());
|
|
CleanupBuffer.set_size(Scope.getCleanupSize());
|
|
EHScopeStack::Cleanup *Fn =
|
|
reinterpret_cast<EHScopeStack::Cleanup*>(CleanupBuffer.data());
|
|
|
|
EHScopeStack::Cleanup::Flags cleanupFlags;
|
|
if (Scope.isNormalCleanup())
|
|
cleanupFlags.setIsNormalCleanupKind();
|
|
if (Scope.isEHCleanup())
|
|
cleanupFlags.setIsEHCleanupKind();
|
|
|
|
if (!RequiresNormalCleanup) {
|
|
destroyOptimisticNormalEntry(*this, Scope);
|
|
EHStack.popCleanup();
|
|
} else {
|
|
// If we have a fallthrough and no other need for the cleanup,
|
|
// emit it directly.
|
|
if (HasFallthrough && !HasPrebranchedFallthrough &&
|
|
!HasFixups && !HasExistingBranches) {
|
|
|
|
destroyOptimisticNormalEntry(*this, Scope);
|
|
EHStack.popCleanup();
|
|
|
|
EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
|
|
|
|
// Otherwise, the best approach is to thread everything through
|
|
// the cleanup block and then try to clean up after ourselves.
|
|
} else {
|
|
// Force the entry block to exist.
|
|
llvm::BasicBlock *NormalEntry = CreateNormalEntry(*this, Scope);
|
|
|
|
// I. Set up the fallthrough edge in.
|
|
|
|
CGBuilderTy::InsertPoint savedInactiveFallthroughIP;
|
|
|
|
// If there's a fallthrough, we need to store the cleanup
|
|
// destination index. For fall-throughs this is always zero.
|
|
if (HasFallthrough) {
|
|
if (!HasPrebranchedFallthrough)
|
|
Builder.CreateStore(Builder.getInt32(0), getNormalCleanupDestSlot());
|
|
|
|
// Otherwise, save and clear the IP if we don't have fallthrough
|
|
// because the cleanup is inactive.
|
|
} else if (FallthroughSource) {
|
|
assert(!IsActive && "source without fallthrough for active cleanup");
|
|
savedInactiveFallthroughIP = Builder.saveAndClearIP();
|
|
}
|
|
|
|
// II. Emit the entry block. This implicitly branches to it if
|
|
// we have fallthrough. All the fixups and existing branches
|
|
// should already be branched to it.
|
|
EmitBlock(NormalEntry);
|
|
|
|
// III. Figure out where we're going and build the cleanup
|
|
// epilogue.
|
|
|
|
bool HasEnclosingCleanups =
|
|
(Scope.getEnclosingNormalCleanup() != EHStack.stable_end());
|
|
|
|
// Compute the branch-through dest if we need it:
|
|
// - if there are branch-throughs threaded through the scope
|
|
// - if fall-through is a branch-through
|
|
// - if there are fixups that will be optimistically forwarded
|
|
// to the enclosing cleanup
|
|
llvm::BasicBlock *BranchThroughDest = 0;
|
|
if (Scope.hasBranchThroughs() ||
|
|
(FallthroughSource && FallthroughIsBranchThrough) ||
|
|
(HasFixups && HasEnclosingCleanups)) {
|
|
assert(HasEnclosingCleanups);
|
|
EHScope &S = *EHStack.find(Scope.getEnclosingNormalCleanup());
|
|
BranchThroughDest = CreateNormalEntry(*this, cast<EHCleanupScope>(S));
|
|
}
|
|
|
|
llvm::BasicBlock *FallthroughDest = 0;
|
|
SmallVector<llvm::Instruction*, 2> InstsToAppend;
|
|
|
|
// If there's exactly one branch-after and no other threads,
|
|
// we can route it without a switch.
|
|
if (!Scope.hasBranchThroughs() && !HasFixups && !HasFallthrough &&
|
|
Scope.getNumBranchAfters() == 1) {
|
|
assert(!BranchThroughDest || !IsActive);
|
|
|
|
// TODO: clean up the possibly dead stores to the cleanup dest slot.
|
|
llvm::BasicBlock *BranchAfter = Scope.getBranchAfterBlock(0);
|
|
InstsToAppend.push_back(llvm::BranchInst::Create(BranchAfter));
|
|
|
|
// Build a switch-out if we need it:
|
|
// - if there are branch-afters threaded through the scope
|
|
// - if fall-through is a branch-after
|
|
// - if there are fixups that have nowhere left to go and
|
|
// so must be immediately resolved
|
|
} else if (Scope.getNumBranchAfters() ||
|
|
(HasFallthrough && !FallthroughIsBranchThrough) ||
|
|
(HasFixups && !HasEnclosingCleanups)) {
|
|
|
|
llvm::BasicBlock *Default =
|
|
(BranchThroughDest ? BranchThroughDest : getUnreachableBlock());
|
|
|
|
// TODO: base this on the number of branch-afters and fixups
|
|
const unsigned SwitchCapacity = 10;
|
|
|
|
llvm::LoadInst *Load =
|
|
new llvm::LoadInst(getNormalCleanupDestSlot(), "cleanup.dest");
|
|
llvm::SwitchInst *Switch =
|
|
llvm::SwitchInst::Create(Load, Default, SwitchCapacity);
|
|
|
|
InstsToAppend.push_back(Load);
|
|
InstsToAppend.push_back(Switch);
|
|
|
|
// Branch-after fallthrough.
|
|
if (FallthroughSource && !FallthroughIsBranchThrough) {
|
|
FallthroughDest = createBasicBlock("cleanup.cont");
|
|
if (HasFallthrough)
|
|
Switch->addCase(Builder.getInt32(0), FallthroughDest);
|
|
}
|
|
|
|
for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) {
|
|
Switch->addCase(Scope.getBranchAfterIndex(I),
|
|
Scope.getBranchAfterBlock(I));
|
|
}
|
|
|
|
// If there aren't any enclosing cleanups, we can resolve all
|
|
// the fixups now.
|
|
if (HasFixups && !HasEnclosingCleanups)
|
|
ResolveAllBranchFixups(*this, Switch, NormalEntry);
|
|
} else {
|
|
// We should always have a branch-through destination in this case.
|
|
assert(BranchThroughDest);
|
|
InstsToAppend.push_back(llvm::BranchInst::Create(BranchThroughDest));
|
|
}
|
|
|
|
// IV. Pop the cleanup and emit it.
|
|
EHStack.popCleanup();
|
|
assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups);
|
|
|
|
EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
|
|
|
|
// Append the prepared cleanup prologue from above.
|
|
llvm::BasicBlock *NormalExit = Builder.GetInsertBlock();
|
|
for (unsigned I = 0, E = InstsToAppend.size(); I != E; ++I)
|
|
NormalExit->getInstList().push_back(InstsToAppend[I]);
|
|
|
|
// Optimistically hope that any fixups will continue falling through.
|
|
for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
|
|
I < E; ++I) {
|
|
BranchFixup &Fixup = EHStack.getBranchFixup(I);
|
|
if (!Fixup.Destination) continue;
|
|
if (!Fixup.OptimisticBranchBlock) {
|
|
new llvm::StoreInst(Builder.getInt32(Fixup.DestinationIndex),
|
|
getNormalCleanupDestSlot(),
|
|
Fixup.InitialBranch);
|
|
Fixup.InitialBranch->setSuccessor(0, NormalEntry);
|
|
}
|
|
Fixup.OptimisticBranchBlock = NormalExit;
|
|
}
|
|
|
|
// V. Set up the fallthrough edge out.
|
|
|
|
// Case 1: a fallthrough source exists but doesn't branch to the
|
|
// cleanup because the cleanup is inactive.
|
|
if (!HasFallthrough && FallthroughSource) {
|
|
// Prebranched fallthrough was forwarded earlier.
|
|
// Non-prebranched fallthrough doesn't need to be forwarded.
|
|
// Either way, all we need to do is restore the IP we cleared before.
|
|
assert(!IsActive);
|
|
Builder.restoreIP(savedInactiveFallthroughIP);
|
|
|
|
// Case 2: a fallthrough source exists and should branch to the
|
|
// cleanup, but we're not supposed to branch through to the next
|
|
// cleanup.
|
|
} else if (HasFallthrough && FallthroughDest) {
|
|
assert(!FallthroughIsBranchThrough);
|
|
EmitBlock(FallthroughDest);
|
|
|
|
// Case 3: a fallthrough source exists and should branch to the
|
|
// cleanup and then through to the next.
|
|
} else if (HasFallthrough) {
|
|
// Everything is already set up for this.
|
|
|
|
// Case 4: no fallthrough source exists.
|
|
} else {
|
|
Builder.ClearInsertionPoint();
|
|
}
|
|
|
|
// VI. Assorted cleaning.
|
|
|
|
// Check whether we can merge NormalEntry into a single predecessor.
|
|
// This might invalidate (non-IR) pointers to NormalEntry.
|
|
llvm::BasicBlock *NewNormalEntry =
|
|
SimplifyCleanupEntry(*this, NormalEntry);
|
|
|
|
// If it did invalidate those pointers, and NormalEntry was the same
|
|
// as NormalExit, go back and patch up the fixups.
|
|
if (NewNormalEntry != NormalEntry && NormalEntry == NormalExit)
|
|
for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
|
|
I < E; ++I)
|
|
EHStack.getBranchFixup(I).OptimisticBranchBlock = NewNormalEntry;
|
|
}
|
|
}
|
|
|
|
assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0);
|
|
|
|
// Emit the EH cleanup if required.
|
|
if (RequiresEHCleanup) {
|
|
if (CGDebugInfo *DI = getDebugInfo())
|
|
DI->EmitLocation(Builder, CurEHLocation);
|
|
|
|
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
|
|
|
|
EmitBlock(EHEntry);
|
|
|
|
// We only actually emit the cleanup code if the cleanup is either
|
|
// active or was used before it was deactivated.
|
|
if (EHActiveFlag || IsActive) {
|
|
|
|
cleanupFlags.setIsForEHCleanup();
|
|
EmitCleanup(*this, Fn, cleanupFlags, EHActiveFlag);
|
|
}
|
|
|
|
Builder.CreateBr(getEHDispatchBlock(EHParent));
|
|
|
|
Builder.restoreIP(SavedIP);
|
|
|
|
SimplifyCleanupEntry(*this, EHEntry);
|
|
}
|
|
}
|
|
|
|
/// isObviouslyBranchWithoutCleanups - Return true if a branch to the
|
|
/// specified destination obviously has no cleanups to run. 'false' is always
|
|
/// a conservatively correct answer for this method.
|
|
bool CodeGenFunction::isObviouslyBranchWithoutCleanups(JumpDest Dest) const {
|
|
assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
|
|
&& "stale jump destination");
|
|
|
|
// Calculate the innermost active normal cleanup.
|
|
EHScopeStack::stable_iterator TopCleanup =
|
|
EHStack.getInnermostActiveNormalCleanup();
|
|
|
|
// If we're not in an active normal cleanup scope, or if the
|
|
// destination scope is within the innermost active normal cleanup
|
|
// scope, we don't need to worry about fixups.
|
|
if (TopCleanup == EHStack.stable_end() ||
|
|
TopCleanup.encloses(Dest.getScopeDepth())) // works for invalid
|
|
return true;
|
|
|
|
// Otherwise, we might need some cleanups.
|
|
return false;
|
|
}
|
|
|
|
|
|
/// Terminate the current block by emitting a branch which might leave
|
|
/// the current cleanup-protected scope. The target scope may not yet
|
|
/// be known, in which case this will require a fixup.
|
|
///
|
|
/// As a side-effect, this method clears the insertion point.
|
|
void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) {
|
|
assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
|
|
&& "stale jump destination");
|
|
|
|
if (!HaveInsertPoint())
|
|
return;
|
|
|
|
// Create the branch.
|
|
llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock());
|
|
|
|
// Calculate the innermost active normal cleanup.
|
|
EHScopeStack::stable_iterator
|
|
TopCleanup = EHStack.getInnermostActiveNormalCleanup();
|
|
|
|
// If we're not in an active normal cleanup scope, or if the
|
|
// destination scope is within the innermost active normal cleanup
|
|
// scope, we don't need to worry about fixups.
|
|
if (TopCleanup == EHStack.stable_end() ||
|
|
TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid
|
|
Builder.ClearInsertionPoint();
|
|
return;
|
|
}
|
|
|
|
// If we can't resolve the destination cleanup scope, just add this
|
|
// to the current cleanup scope as a branch fixup.
|
|
if (!Dest.getScopeDepth().isValid()) {
|
|
BranchFixup &Fixup = EHStack.addBranchFixup();
|
|
Fixup.Destination = Dest.getBlock();
|
|
Fixup.DestinationIndex = Dest.getDestIndex();
|
|
Fixup.InitialBranch = BI;
|
|
Fixup.OptimisticBranchBlock = 0;
|
|
|
|
Builder.ClearInsertionPoint();
|
|
return;
|
|
}
|
|
|
|
// Otherwise, thread through all the normal cleanups in scope.
|
|
|
|
// Store the index at the start.
|
|
llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex());
|
|
new llvm::StoreInst(Index, getNormalCleanupDestSlot(), BI);
|
|
|
|
// Adjust BI to point to the first cleanup block.
|
|
{
|
|
EHCleanupScope &Scope =
|
|
cast<EHCleanupScope>(*EHStack.find(TopCleanup));
|
|
BI->setSuccessor(0, CreateNormalEntry(*this, Scope));
|
|
}
|
|
|
|
// Add this destination to all the scopes involved.
|
|
EHScopeStack::stable_iterator I = TopCleanup;
|
|
EHScopeStack::stable_iterator E = Dest.getScopeDepth();
|
|
if (E.strictlyEncloses(I)) {
|
|
while (true) {
|
|
EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I));
|
|
assert(Scope.isNormalCleanup());
|
|
I = Scope.getEnclosingNormalCleanup();
|
|
|
|
// If this is the last cleanup we're propagating through, tell it
|
|
// that there's a resolved jump moving through it.
|
|
if (!E.strictlyEncloses(I)) {
|
|
Scope.addBranchAfter(Index, Dest.getBlock());
|
|
break;
|
|
}
|
|
|
|
// Otherwise, tell the scope that there's a jump propoagating
|
|
// through it. If this isn't new information, all the rest of
|
|
// the work has been done before.
|
|
if (!Scope.addBranchThrough(Dest.getBlock()))
|
|
break;
|
|
}
|
|
}
|
|
|
|
Builder.ClearInsertionPoint();
|
|
}
|
|
|
|
static bool IsUsedAsNormalCleanup(EHScopeStack &EHStack,
|
|
EHScopeStack::stable_iterator C) {
|
|
// If we needed a normal block for any reason, that counts.
|
|
if (cast<EHCleanupScope>(*EHStack.find(C)).getNormalBlock())
|
|
return true;
|
|
|
|
// Check whether any enclosed cleanups were needed.
|
|
for (EHScopeStack::stable_iterator
|
|
I = EHStack.getInnermostNormalCleanup();
|
|
I != C; ) {
|
|
assert(C.strictlyEncloses(I));
|
|
EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
|
|
if (S.getNormalBlock()) return true;
|
|
I = S.getEnclosingNormalCleanup();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool IsUsedAsEHCleanup(EHScopeStack &EHStack,
|
|
EHScopeStack::stable_iterator cleanup) {
|
|
// If we needed an EH block for any reason, that counts.
|
|
if (EHStack.find(cleanup)->hasEHBranches())
|
|
return true;
|
|
|
|
// Check whether any enclosed cleanups were needed.
|
|
for (EHScopeStack::stable_iterator
|
|
i = EHStack.getInnermostEHScope(); i != cleanup; ) {
|
|
assert(cleanup.strictlyEncloses(i));
|
|
|
|
EHScope &scope = *EHStack.find(i);
|
|
if (scope.hasEHBranches())
|
|
return true;
|
|
|
|
i = scope.getEnclosingEHScope();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
enum ForActivation_t {
|
|
ForActivation,
|
|
ForDeactivation
|
|
};
|
|
|
|
/// The given cleanup block is changing activation state. Configure a
|
|
/// cleanup variable if necessary.
|
|
///
|
|
/// It would be good if we had some way of determining if there were
|
|
/// extra uses *after* the change-over point.
|
|
static void SetupCleanupBlockActivation(CodeGenFunction &CGF,
|
|
EHScopeStack::stable_iterator C,
|
|
ForActivation_t kind,
|
|
llvm::Instruction *dominatingIP) {
|
|
EHCleanupScope &Scope = cast<EHCleanupScope>(*CGF.EHStack.find(C));
|
|
|
|
// We always need the flag if we're activating the cleanup in a
|
|
// conditional context, because we have to assume that the current
|
|
// location doesn't necessarily dominate the cleanup's code.
|
|
bool isActivatedInConditional =
|
|
(kind == ForActivation && CGF.isInConditionalBranch());
|
|
|
|
bool needFlag = false;
|
|
|
|
// Calculate whether the cleanup was used:
|
|
|
|
// - as a normal cleanup
|
|
if (Scope.isNormalCleanup() &&
|
|
(isActivatedInConditional || IsUsedAsNormalCleanup(CGF.EHStack, C))) {
|
|
Scope.setTestFlagInNormalCleanup();
|
|
needFlag = true;
|
|
}
|
|
|
|
// - as an EH cleanup
|
|
if (Scope.isEHCleanup() &&
|
|
(isActivatedInConditional || IsUsedAsEHCleanup(CGF.EHStack, C))) {
|
|
Scope.setTestFlagInEHCleanup();
|
|
needFlag = true;
|
|
}
|
|
|
|
// If it hasn't yet been used as either, we're done.
|
|
if (!needFlag) return;
|
|
|
|
llvm::AllocaInst *var = Scope.getActiveFlag();
|
|
if (!var) {
|
|
var = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "cleanup.isactive");
|
|
Scope.setActiveFlag(var);
|
|
|
|
assert(dominatingIP && "no existing variable and no dominating IP!");
|
|
|
|
// Initialize to true or false depending on whether it was
|
|
// active up to this point.
|
|
llvm::Value *value = CGF.Builder.getInt1(kind == ForDeactivation);
|
|
|
|
// If we're in a conditional block, ignore the dominating IP and
|
|
// use the outermost conditional branch.
|
|
if (CGF.isInConditionalBranch()) {
|
|
CGF.setBeforeOutermostConditional(value, var);
|
|
} else {
|
|
new llvm::StoreInst(value, var, dominatingIP);
|
|
}
|
|
}
|
|
|
|
CGF.Builder.CreateStore(CGF.Builder.getInt1(kind == ForActivation), var);
|
|
}
|
|
|
|
/// Activate a cleanup that was created in an inactivated state.
|
|
void CodeGenFunction::ActivateCleanupBlock(EHScopeStack::stable_iterator C,
|
|
llvm::Instruction *dominatingIP) {
|
|
assert(C != EHStack.stable_end() && "activating bottom of stack?");
|
|
EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
|
|
assert(!Scope.isActive() && "double activation");
|
|
|
|
SetupCleanupBlockActivation(*this, C, ForActivation, dominatingIP);
|
|
|
|
Scope.setActive(true);
|
|
}
|
|
|
|
/// Deactive a cleanup that was created in an active state.
|
|
void CodeGenFunction::DeactivateCleanupBlock(EHScopeStack::stable_iterator C,
|
|
llvm::Instruction *dominatingIP) {
|
|
assert(C != EHStack.stable_end() && "deactivating bottom of stack?");
|
|
EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
|
|
assert(Scope.isActive() && "double deactivation");
|
|
|
|
// If it's the top of the stack, just pop it.
|
|
if (C == EHStack.stable_begin()) {
|
|
// If it's a normal cleanup, we need to pretend that the
|
|
// fallthrough is unreachable.
|
|
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
|
|
PopCleanupBlock();
|
|
Builder.restoreIP(SavedIP);
|
|
return;
|
|
}
|
|
|
|
// Otherwise, follow the general case.
|
|
SetupCleanupBlockActivation(*this, C, ForDeactivation, dominatingIP);
|
|
|
|
Scope.setActive(false);
|
|
}
|
|
|
|
llvm::Value *CodeGenFunction::getNormalCleanupDestSlot() {
|
|
if (!NormalCleanupDest)
|
|
NormalCleanupDest =
|
|
CreateTempAlloca(Builder.getInt32Ty(), "cleanup.dest.slot");
|
|
return NormalCleanupDest;
|
|
}
|
|
|
|
/// Emits all the code to cause the given temporary to be cleaned up.
|
|
void CodeGenFunction::EmitCXXTemporary(const CXXTemporary *Temporary,
|
|
QualType TempType,
|
|
llvm::Value *Ptr) {
|
|
pushDestroy(NormalAndEHCleanup, Ptr, TempType, destroyCXXObject,
|
|
/*useEHCleanup*/ true);
|
|
}
|