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SEH: Emit the constant filter 1 as a catch-all 

Minor optimization of code like __try { ... } __except(1) { ... }.

llvm-svn: 226766
This commit is contained in:
Reid Kleckner 2015-01-22 02:25:56 +00:00
parent f1f4bc2176
commit 2a2e156318
2 changed files with 17 additions and 7 deletions
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12
clang/lib/CodeGen/CGException.cpp
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@ -1839,6 +1839,18 @@ void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
SEHExceptStmt *Except = S.getExceptHandler();
assert(Except);
EHCatchScope *CatchScope = EHStack.pushCatch(1);
// If the filter is known to evaluate to 1, then we can use the clause "catch
// i8* null".
llvm::Constant *C =
CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
if (C && C->isOneValue()) {
CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
return;
}
// In general, we have to emit an outlined filter function. Use the function
// in place of the RTTI typeinfo global that C++ EH uses.
CodeGenFunction FilterCGF(CGM, /*suppressNewContext=*/true);
llvm::Function *FilterFunc =
FilterCGF.GenerateSEHFilterFunction(*this, *Except);

12
clang/test/CodeGen/exceptions-seh.c
View File

@ -26,13 +26,11 @@ int safe_div(int numerator, int denominator, int *res) {
//
// CHECK: [[lpad]]
// CHECK: landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*)
// CHECK: %[[sel:[^ ]*]] = load i32*
// CHECK: %[[filt_id:[^ ]*]] = call i32 @llvm.eh.typeid.for(i8* bitcast (i32 (i8*, i8*)* @"\01?filt$0@0@safe_div@@" to i8*))
// CHECK: %[[matches:[^ ]*]] = icmp eq i32 %[[sel]], %[[filt_id]]
// CHECK: br i1 %[[matches]], label %[[except_bb:[^ ]*]], label %{{.*}}
//
// CHECK: [[except_bb]]
// CHECK: store i32 -42, i32* %[[success:[^ ]*]]
// CHECK-NEXT: catch i8* null
// CHECK-NOT: br i1
// CHECK: br label %[[except:[^ ]*]]
// CHECK: [[except]]
// CHECK-NEXT: store i32 -42, i32* %[[success:[^ ]*]]
//
// CHECK: %[[res:[^ ]*]] = load i32* %[[success]]
// CHECK: ret i32 %[[res]]