leonardchan added a comment.
Herald added a subscriber: jdoerfert.
Hi @pcc , I'm working on revisiting this to see if this could help when
building Fuchsia (D58321 <https://reviews.llvm.org/D58321>) and had a few
questions I left inline.
================
Comment at: lib/CodeGen/CGVTables.cpp:532
+ for (auto &Comp : VTLayout.vtable_components()) {
+ if (Comp.isFunctionPointerKind())
+ Types.push_back(CGM.Int32Ty);
----------------
It seems that the condition for treating a vtable component as an i32 vs i8* is
slightly different here than in `SetVTableInitializer`. `SetVTableInitializer`
checks
```
Component.isFunctionPointerKind() && (I == 0 || !Components[I -
1].isFunctionPointerKind())
```
where `GetVTableType` just checks `Component.isFunctionPointerKind()`.
Should this also check if the first or last component is a function pointer,
and does this check in `SetVTableInitializer` have any importance with the
FIXME below it?
================
Comment at: test/CodeGenCXX/vtable-relative-abi.cpp:5
+
+// CHECK-ITANIUM: @_ZTV1S = hidden unnamed_addr constant { i8*, i8*, i32, i32
} { i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI1S to i8*), i32 trunc (i64 sub
(i64 ptrtoint (void (%struct.S*)* @_ZN1S2f1Ev to i64), i64 ptrtoint (i32*
getelementptr inbounds ({ i8*, i8*, i32, i32 }, { i8*, i8*, i32, i32 }*
@_ZTV1S, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void
(%struct.S*)* @_ZN1S2f2Ev to i64), i64 ptrtoint (i32* getelementptr inbounds ({
i8*, i8*, i32, i32 }, { i8*, i8*, i32, i32 }* @_ZTV1S, i32 0, i32 2) to i64))
to i32) }, align 8
+// CHECK-MS: @0 = private unnamed_addr constant { i8*, i32, i32 } { i8*
bitcast (%rtti.CompleteObjectLocator* @"\01??_R4S@@6B@" to i8*), i32 trunc (i64
sub (i64 ptrtoint (void (%struct.S*)* @"\01?f1@S@@UEAAXXZ" to i64), i64
ptrtoint (i32* getelementptr inbounds ({ i8*, i32, i32 }, { i8*, i32, i32 }*
@0, i32 0, i32 1) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void
(%struct.S*)* @"\01?f2@S@@UEAAXXZ" to i64), i64 ptrtoint (i32* getelementptr
inbounds ({ i8*, i32, i32 }, { i8*, i32, i32 }* @0, i32 0, i32 1) to i64)) to
i32) }, comdat($"\01??_7S@@6B@")
----------------
Should the second `getelementptr` access be `i32 0, i32 3` instead since it’s
for the 4th element in the struct?
If so, I think this is due to some referencing problem with the
`maybeMakeRelative` lambda. I ran into this issue when I moved `llvm::Type
*VTableTy = VTable->getValueType();` into the following if block that
initializes `AddrPointInt`. This also seems to occur for other test classes
that contain more than one virtual function.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D20749/new/
https://reviews.llvm.org/D20749
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