ahatanak created this revision.
Herald added subscribers: kristof.beyls, aemerson.
The assertion failure occurs when a setter is called using the dot syntax to
set a property of a class type that doesn't have trivial copy/move constructors
or assignment operators. It happens only when clang is compiling for c++1z and
copy elision allows avoiding copying a temporary to the argument passed to the
setter method in Sema.
For example:
struct S2 {
id f1;
};
@interface C
@property S2 f;
@end
@implementation C
@end
void test(C *c) {
c.f = S2();
}
When IRGen visits the ObjCMessageExpr for the call to the setter, it tries to
emit a copy of an S2 object that has been constructed (this happens in
AggExprEmitter::VisitOpaqueValueExpr) and the assertion in
CodeGenFunction::EmitAggregateCopy fails because S2 doesn't have the trivial
special functions needed to do the copy.
This is the AST of the ObjCMessageExpr:
`-ObjCMessageExpr 0x7fe03c06b730 <col:5> 'void' selector=setF:
| |-OpaqueValueExpr 0x7fe03c06b698 <col:3> 'C *'
| | `-ImplicitCastExpr 0x7fe03c06b5e0 <col:3> 'C *' <LValueToRValue>
| | `-DeclRefExpr 0x7fe03c06b5b8 <col:3> 'C *__strong' lvalue
ParmVar 0x7fe03c06b408 'c' 'C *__strong'
| `-OpaqueValueExpr 0x7fe03c06b6e8 <col:9, col:12> 'struct S2'
| `-CXXBindTemporaryExpr 0x7fe03c06b678 <col:9, col:12> 'struct S2'
(CXXTemporary 0x7fe03c06b670)
| `-CXXTemporaryObjectExpr 0x7fe03c06b638 <col:9, col:12> 'struct
S2' 'void (void)'
To avoid the crash, I modified CodeGenFunction::EmitAnyExprToTemp to return the
value for the OpaqueValueExpr (which must have already been evaluated when it's
visited, I think) so that it doesn't have to call EmitAggregateCopy to make a
copy.
I'm actually unsure whether we should fix Sema and change the AST
representation or fix IRGen as I did in this patch. I'm open to suggestions if
anyone has a better idea to fix the crash.
https://reviews.llvm.org/D39562
Files:
lib/CodeGen/CGExpr.cpp
test/CodeGenObjCXX/property-dot-copy-elision.mm
test/CodeGenObjCXX/property-objects.mm
Index: test/CodeGenObjCXX/property-objects.mm
===================================================================
--- test/CodeGenObjCXX/property-objects.mm
+++ test/CodeGenObjCXX/property-objects.mm
@@ -125,8 +125,6 @@
// CHECK-NEXT: [[T1:%.*]] = sext i32 [[T0]] to i64
// CHECK-NEXT: store i64 [[T1]], i64* [[X]], align 8
// CHECK-NOT: call
-// CHECK: call void @llvm.memcpy
-// CHECK-NOT: call
// CHECK: call void bitcast {{.*}} @objc_msgSend
// CHECK-NOT: call
// CHECK: ret void
@@ -147,8 +145,6 @@
// CHECK-NOT: call
// CHECK: store i64 [[T0]],
// CHECK-NOT: call
-// CHECK: call void @llvm.memcpy
-// CHECK-NOT: call
// CHECK: call void bitcast {{.*}} @objc_msgSend
// CHECK-NOT: call
// CHECK: ret void
@@ -168,8 +164,6 @@
// CHECK-NOT: call
// CHECK: store i64 [[T0]],
// CHECK-NOT: call
-// CHECK: call void @llvm.memcpy
-// CHECK-NOT: call
// CHECK: call void bitcast {{.*}} @objc_msgSend
// CHECK-NOT: call
// CHECK: ret void
@@ -216,8 +210,6 @@
// CHECK-NOT: call
// CHECK: store i32 [[T0]],
// CHECK-NOT: call
-// CHECK: call void @llvm.memcpy
-// CHECK-NOT: call
// CHECK: call void bitcast {{.*}} @objc_msgSend
// CHECK-NOT: call
// CHECK: ret void
Index: test/CodeGenObjCXX/property-dot-copy-elision.mm
===================================================================
--- /dev/null
+++ test/CodeGenObjCXX/property-dot-copy-elision.mm
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -std=c++1z -fobjc-arc -o - %s | FileCheck %s
+
+struct S0 {
+ id f;
+};
+
+struct S1 {
+ S1();
+ S1(S0);
+ id f;
+};
+
+@interface C
+@property S1 f;
+@end
+@implementation C
+@end
+
+// CHECK-LABEL: define void @_Z5test0P1C(
+// CHECK: %{{.*}} = alloca %
+// CHECK: %[[TEMP_LVALUE:.*]] = alloca %[[STRUCT_S0:.*]], align
+// CHECK: %[[AGG_TMP:.*]] = alloca %[[STRUCT_S1:.*]], align
+// CHECK: call void @_ZN2S0C1Ev(%[[STRUCT_S0]]* %[[TEMP_LVALUE]])
+// CHECK: call void @_ZN2S1C1E2S0(%[[STRUCT_S1]]* %[[AGG_TMP]], %[[STRUCT_S0]]* %[[TEMP_LVALUE]])
+// CHECK: call void bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to void (i8*, i8*, %[[STRUCT_S1]]*)*)(i8* %{{.*}}, i8* %{{.*}}, %[[STRUCT_S1]]* %[[AGG_TMP]])
+
+void test0(C *c) {
+ c.f = S0();
+}
+
+// CHECK: define void @_Z5test1P1C(
+// CHECK: %{{.*}} = alloca %
+// CHECK: %[[TEMP_LVALUE:.*]] = alloca %[[STRUCT_S1:.*]], align
+// CHECK: call void @_ZN2S1C1Ev(%[[STRUCT_S1]]* %[[TEMP_LVALUE]])
+// CHECK: call void bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to void (i8*, i8*, %[[STRUCT_S1]]*)*)(i8* %{{.*}}, i8* %{{.*}}, %[[STRUCT_S1]]* %[[TEMP_LVALUE]])
+
+void test1(C *c) {
+ c.f = S1();
+}
Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -192,8 +192,12 @@
RValue CodeGenFunction::EmitAnyExprToTemp(const Expr *E) {
AggValueSlot AggSlot = AggValueSlot::ignored();
- if (hasAggregateEvaluationKind(E->getType()))
+ if (hasAggregateEvaluationKind(E->getType())) {
+ if (const auto *OVE = dyn_cast<OpaqueValueExpr>(E))
+ return getOpaqueLValueMapping(OVE).asAggregateRValue();
AggSlot = CreateAggTemp(E->getType(), "agg.tmp");
+ }
+
return EmitAnyExpr(E, AggSlot);
}
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