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Evaluate compound literals directly into the result aggregate 

when that aggregate isn't potentially aliased.

llvm-svn: 176654
This commit is contained in:
John McCall 2013-03-07 21:36:54 +00:00
parent 95e1936477
commit bea4c3d8c4
2 changed files with 36 additions and 4 deletions
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6
clang/lib/CodeGen/CGExprAgg.cpp
View File

@ -531,12 +531,10 @@ void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
void
AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
if (E->getType().isPODType(CGF.getContext())) {
if (Dest.isPotentiallyAliased() &&
E->getType().isPODType(CGF.getContext())) {
// For a POD type, just emit a load of the lvalue + a copy, because our
// compound literal might alias the destination.
// FIXME: This is a band-aid; the real problem appears to be in our handling
// of assignments, where we store directly into the LHS without checking
// whether anything in the RHS aliases.
EmitAggLoadOfLValue(E);
return;
}

34
clang/test/CodeGen/compound-literal.c
View File

@ -32,3 +32,37 @@ void f() {
s = (S){s.y,s.x};
// CHECK-NEXT: ret void
}
// CHECK: define i48 @g(
struct G { short x, y, z; };
struct G g(int x, int y, int z) {
// CHECK: [[RESULT:%.*]] = alloca [[G:%.*]], align 2
// CHECK-NEXT: [[X:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[Y:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[Z:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[COERCE_TEMP:%.*]] = alloca i48
// CHECK-NEXT: store i32
// CHECK-NEXT: store i32
// CHECK-NEXT: store i32
// Evaluate the compound literal directly in the result value slot.
// CHECK-NEXT: [[T0:%.*]] = getelementptr inbounds [[G]]* [[RESULT]], i32 0, i32 0
// CHECK-NEXT: [[T1:%.*]] = load i32* [[X]], align 4
// CHECK-NEXT: [[T2:%.*]] = trunc i32 [[T1]] to i16
// CHECK-NEXT: store i16 [[T2]], i16* [[T0]], align 2
// CHECK-NEXT: [[T0:%.*]] = getelementptr inbounds [[G]]* [[RESULT]], i32 0, i32 1
// CHECK-NEXT: [[T1:%.*]] = load i32* [[Y]], align 4
// CHECK-NEXT: [[T2:%.*]] = trunc i32 [[T1]] to i16
// CHECK-NEXT: store i16 [[T2]], i16* [[T0]], align 2
// CHECK-NEXT: [[T0:%.*]] = getelementptr inbounds [[G]]* [[RESULT]], i32 0, i32 2
// CHECK-NEXT: [[T1:%.*]] = load i32* [[Z]], align 4
// CHECK-NEXT: [[T2:%.*]] = trunc i32 [[T1]] to i16
// CHECK-NEXT: store i16 [[T2]], i16* [[T0]], align 2
return (struct G) { x, y, z };
// CHECK-NEXT: [[T0:%.*]] = bitcast i48* [[COERCE_TEMP]] to i8*
// CHECK-NEXT: [[T1:%.*]] = bitcast [[G]]* [[RESULT]] to i8*
// CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* [[T0]], i8* [[T1]], i64 6
// CHECK-NEXT: [[T0:%.*]] = load i48* [[COERCE_TEMP]]
// CHECK-NEXT: ret i48 [[T0]]
}