ahatanak created this revision.
ahatanak added reviewers: rjmccall, vsk.
This patch fixes what looks like a bug in IRGen's member initialization where
it uses the alignment of a complete object instead of its non-virtual alignment
when emitting the base constructor.
For example, when emitting the base constructor for B, IRGen uses a 16-byte
alignment to initialize B::x because B's alignment is 16-byte (which is because
A is 16-byte aligned). This is not correct since A is a virtual base of B and
therefore we cannot guarantee that the pointer to B that is passed to the base
constructor is always 16-byte aligned.
struct A {
__attribute__((aligned(16))) double data1;
};
struct B : public virtual A {
B() : x(123) {}
double a;
int x;
};
struct C : public virtual B {};
void test() { B b; C c; }
To fix the bug, this patch calls CGF.MakeNaturalAlignPointeeAddrLValue in
EmitMemberInitializer to create an LValue that uses the non-virtual alignment
of the class.
rdar://problem/36382481
https://reviews.llvm.org/D42521
Files:
lib/CodeGen/CGClass.cpp
test/CodeGenCXX/virtual-bases.cpp
Index: test/CodeGenCXX/virtual-bases.cpp
===================================================================
--- test/CodeGenCXX/virtual-bases.cpp
+++ test/CodeGenCXX/virtual-bases.cpp
@@ -46,3 +46,37 @@
D::D() { }
}
+
+namespace virtualBaseAlignment {
+
+// Check that the store to B::x in the base constructor has an 8-byte
alignment.
+
+// CHECK: define linkonce_odr void
@_ZN20virtualBaseAlignment1BC1Ev(%[[STRUCT_B:.*]]* %[[THIS:.*]])
+// CHECK: %[[THIS_ADDR:.*]] = alloca %[[STRUCT_B]]*, align 8
+// CHECK: store %[[STRUCT_B]]* %[[THIS]], %[[STRUCT_B]]** %[[THIS_ADDR]],
align 8
+// CHECK: %[[THIS1:.*]] = load %[[STRUCT_B]]*, %[[STRUCT_B]]** %[[THIS_ADDR]],
align 8
+// CHECK: %[[X:.*]] = getelementptr inbounds %[[STRUCT_B]], %[[STRUCT_B]]*
%[[THIS1]], i32 0, i32 2
+// CHECK: store i32 123, i32* %[[X]], align 16
+
+// CHECK: define linkonce_odr void
@_ZN20virtualBaseAlignment1BC2Ev(%[[STRUCT_B]]* %[[THIS:.*]], i8** %{{.*}})
+// CHECK: %[[THIS_ADDR:.*]] = alloca %[[STRUCT_B]]*, align 8
+// CHECK: store %[[STRUCT_B]]* %[[THIS]], %[[STRUCT_B]]** %[[THIS_ADDR]],
align 8
+// CHECK: %[[THIS1:.*]] = load %[[STRUCT_B]]*, %[[STRUCT_B]]** %[[THIS_ADDR]],
align 8
+// CHECK: %[[X:.*]] = getelementptr inbounds %[[STRUCT_B]], %[[STRUCT_B]]*
%[[THIS1]], i32 0, i32 2
+// CHECK: store i32 123, i32* %[[X]], align 8
+
+struct A {
+ __attribute__((aligned(16))) double data1;
+};
+
+struct B : public virtual A {
+ B() : x(123) {}
+ double a;
+ int x;
+};
+
+struct C : public virtual B {};
+
+void test() { B b; C c; }
+
+}
Index: lib/CodeGen/CGClass.cpp
===================================================================
--- lib/CodeGen/CGClass.cpp
+++ lib/CodeGen/CGClass.cpp
@@ -615,7 +615,14 @@
llvm::Value *ThisPtr = CGF.LoadCXXThis();
QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
- LValue LHS = CGF.MakeNaturalAlignAddrLValue(ThisPtr, RecordTy);
+ LValue LHS;
+
+ // If a base constructor is being emitted, create an LValue that has the
+ // non-virtual alignment.
+ if (CGF.CurGD.getCtorType() == Ctor_Base)
+ LHS = CGF.MakeNaturalAlignPointeeAddrLValue(ThisPtr, RecordTy);
+ else
+ LHS = CGF.MakeNaturalAlignAddrLValue(ThisPtr, RecordTy);
EmitLValueForAnyFieldInitialization(CGF, MemberInit, LHS);
Index: test/CodeGenCXX/virtual-bases.cpp
===================================================================
--- test/CodeGenCXX/virtual-bases.cpp
+++ test/CodeGenCXX/virtual-bases.cpp
@@ -46,3 +46,37 @@
D::D() { }
}
+
+namespace virtualBaseAlignment {
+
+// Check that the store to B::x in the base constructor has an 8-byte alignment.
+
+// CHECK: define linkonce_odr void @_ZN20virtualBaseAlignment1BC1Ev(%[[STRUCT_B:.*]]* %[[THIS:.*]])
+// CHECK: %[[THIS_ADDR:.*]] = alloca %[[STRUCT_B]]*, align 8
+// CHECK: store %[[STRUCT_B]]* %[[THIS]], %[[STRUCT_B]]** %[[THIS_ADDR]], align 8
+// CHECK: %[[THIS1:.*]] = load %[[STRUCT_B]]*, %[[STRUCT_B]]** %[[THIS_ADDR]], align 8
+// CHECK: %[[X:.*]] = getelementptr inbounds %[[STRUCT_B]], %[[STRUCT_B]]* %[[THIS1]], i32 0, i32 2
+// CHECK: store i32 123, i32* %[[X]], align 16
+
+// CHECK: define linkonce_odr void @_ZN20virtualBaseAlignment1BC2Ev(%[[STRUCT_B]]* %[[THIS:.*]], i8** %{{.*}})
+// CHECK: %[[THIS_ADDR:.*]] = alloca %[[STRUCT_B]]*, align 8
+// CHECK: store %[[STRUCT_B]]* %[[THIS]], %[[STRUCT_B]]** %[[THIS_ADDR]], align 8
+// CHECK: %[[THIS1:.*]] = load %[[STRUCT_B]]*, %[[STRUCT_B]]** %[[THIS_ADDR]], align 8
+// CHECK: %[[X:.*]] = getelementptr inbounds %[[STRUCT_B]], %[[STRUCT_B]]* %[[THIS1]], i32 0, i32 2
+// CHECK: store i32 123, i32* %[[X]], align 8
+
+struct A {
+ __attribute__((aligned(16))) double data1;
+};
+
+struct B : public virtual A {
+ B() : x(123) {}
+ double a;
+ int x;
+};
+
+struct C : public virtual B {};
+
+void test() { B b; C c; }
+
+}
Index: lib/CodeGen/CGClass.cpp
===================================================================
--- lib/CodeGen/CGClass.cpp
+++ lib/CodeGen/CGClass.cpp
@@ -615,7 +615,14 @@
llvm::Value *ThisPtr = CGF.LoadCXXThis();
QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
- LValue LHS = CGF.MakeNaturalAlignAddrLValue(ThisPtr, RecordTy);
+ LValue LHS;
+
+ // If a base constructor is being emitted, create an LValue that has the
+ // non-virtual alignment.
+ if (CGF.CurGD.getCtorType() == Ctor_Base)
+ LHS = CGF.MakeNaturalAlignPointeeAddrLValue(ThisPtr, RecordTy);
+ else
+ LHS = CGF.MakeNaturalAlignAddrLValue(ThisPtr, RecordTy);
EmitLValueForAnyFieldInitialization(CGF, MemberInit, LHS);
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