Implement IRGen for SEH __finally and AbnormalTermination
Previously we would simply double-emit the body of the __finally block,
but that doesn't work when it contains any kind of Decl, which we can't
double emit.
This fixes that by emitting the block once and branching into a shared
code region and then branching back out.
llvm-svn: 228222
diff --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index f94a380..e90f568 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -451,6 +451,12 @@
return Builder.CreateLoad(getEHSelectorSlot(), "sel");
}
+llvm::Value *CodeGenFunction::getAbnormalTerminationSlot() {
+ if (!AbnormalTerminationSlot)
+ AbnormalTerminationSlot = CreateTempAlloca(Int8Ty, "abnormal.termination.slot");
+ return AbnormalTerminationSlot;
+}
+
void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
bool KeepInsertionPoint) {
if (!E->getSubExpr()) {
@@ -1686,18 +1692,45 @@
return;
}
- EnterSEHTryStmt(S);
+ SEHFinallyInfo FI;
+ EnterSEHTryStmt(S, FI);
EmitStmt(S.getTryBlock());
- ExitSEHTryStmt(S);
+ ExitSEHTryStmt(S, FI);
}
namespace {
struct PerformSEHFinally : EHScopeStack::Cleanup {
- Stmt *Block;
- PerformSEHFinally(Stmt *Block) : Block(Block) {}
+ CodeGenFunction::SEHFinallyInfo *FI;
+ PerformSEHFinally(CodeGenFunction::SEHFinallyInfo *FI) : FI(FI) {}
+
void Emit(CodeGenFunction &CGF, Flags F) override {
- // FIXME: Don't double-emit LabelDecls.
- CGF.EmitStmt(Block);
+ // Cleanups are emitted at most twice: once for normal control flow and once
+ // for exception control flow. Branch into the finally block, and remember
+ // the continuation block so we can branch out later.
+ if (!FI->FinallyBB) {
+ FI->FinallyBB = CGF.createBasicBlock("__finally");
+ FI->FinallyBB->insertInto(CGF.CurFn);
+ FI->FinallyBB->moveAfter(CGF.Builder.GetInsertBlock());
+ }
+
+ // Set the termination status and branch in.
+ CGF.Builder.CreateStore(
+ llvm::ConstantInt::get(CGF.Int8Ty, F.isForEHCleanup()),
+ CGF.getAbnormalTerminationSlot());
+ CGF.Builder.CreateBr(FI->FinallyBB);
+
+ // Create a continuation block for normal or exceptional control.
+ if (F.isForEHCleanup()) {
+ assert(!FI->ResumeBB && "double emission for EH");
+ FI->ResumeBB = CGF.createBasicBlock("__finally.resume");
+ CGF.EmitBlock(FI->ResumeBB);
+ } else {
+ assert(F.isForNormalCleanup() && !FI->ContBB && "double normal emission");
+ FI->ContBB = CGF.createBasicBlock("__finally.cont");
+ CGF.EmitBlock(FI->ContBB);
+ // Try to keep source order.
+ FI->ContBB->moveAfter(FI->FinallyBB);
+ }
}
};
}
@@ -1827,11 +1860,17 @@
return Builder.CreateTrunc(Code, CGM.Int32Ty);
}
-void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
+llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
+ // Load from the abnormal termination slot. It will be uninitialized outside
+ // of __finally blocks, which we should warn or error on.
+ llvm::Value *IsEH = Builder.CreateLoad(getAbnormalTerminationSlot());
+ return Builder.CreateZExt(IsEH, Int32Ty);
+}
+
+void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S, SEHFinallyInfo &FI) {
if (SEHFinallyStmt *Finally = S.getFinallyHandler()) {
// Push a cleanup for __finally blocks.
- EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup,
- Finally->getBlock());
+ EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, &FI);
return;
}
@@ -1859,15 +1898,34 @@
CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except"));
}
-void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
+void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S, SEHFinallyInfo &FI) {
// Just pop the cleanup if it's a __finally block.
- if (S.getFinallyHandler()) {
+ if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
PopCleanupBlock();
+
+ // Emit the code into FinallyBB.
+ Builder.SetInsertPoint(FI.FinallyBB);
+ EmitStmt(Finally->getBlock());
+
+ assert(FI.ContBB);
+ if (FI.ResumeBB) {
+ llvm::Value *IsEH = Builder.CreateLoad(getAbnormalTerminationSlot(),
+ "abnormal.termination");
+ IsEH = Builder.CreateICmpEQ(IsEH, llvm::ConstantInt::get(Int8Ty, 0));
+ Builder.CreateCondBr(IsEH, FI.ContBB, FI.ResumeBB);
+ } else {
+ // There was nothing exceptional in the try body, so we only have normal
+ // control flow.
+ Builder.CreateBr(FI.ContBB);
+ }
+
+ Builder.SetInsertPoint(FI.ContBB);
+
return;
}
// Otherwise, we must have an __except block.
- SEHExceptStmt *Except = S.getExceptHandler();
+ const SEHExceptStmt *Except = S.getExceptHandler();
assert(Except && "__try must have __finally xor __except");
EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());