vsapsai added a comment.
In D138859#3954975 <https://reviews.llvm.org/D138859#3954975>, @erichkeane
wrote:
> The hash there isn't the problem, its that you're adding a field to Attr.td
> that isn't serialized in ASTWriter/ASTReader.
That's a good point. Sorry I haven't realized it at first and thanks for your
patience. So, `IsODRHashable` is a property of the attribute kind, not the
attribute instance. Unfortunately, I don't know what is the appropriate way to
fix FIXME below (and how urgent it is).
// FIXME: These are properties of the attribute kind, not state for this
// instance of the attribute.
...
unsigned IsODRHashable : 1;
Anyway, big chunk of attribute deserialization happens in "AttrPCHRead.inc" and
for AMDGPUFlatWorkGroupSizeAttr (non-trivial example) we have
case attr::AMDGPUFlatWorkGroupSize: {
bool isInherited = Record.readInt();
bool isImplicit = Record.readInt();
bool isPackExpansion = Record.readInt();
Expr * min = Record.readExpr();
Expr * max = Record.readExpr();
New = new (Context) AMDGPUFlatWorkGroupSizeAttr(Context, Info, min, max);
cast<InheritableAttr>(New)->setInherited(isInherited);
New->setImplicit(isImplicit);
New->setPackExpansion(isPackExpansion);
break;
}
which calls the generated constructor
AMDGPUFlatWorkGroupSizeAttr::AMDGPUFlatWorkGroupSizeAttr(ASTContext &Ctx,
const AttributeCommonInfo &CommonInfo
, Expr * Min
, Expr * Max
)
: InheritableAttr(Ctx, CommonInfo, attr::AMDGPUFlatWorkGroupSize, false,
false, false)
, min(Min)
, max(Max)
{
}
where `false, false, false` part corresponds to `bool IsLateParsed, bool
IsODRHashable, bool InheritEvenIfAlreadyPresent`. So `IsODRHashable` is never
serialized/deserialized and compiler knows what the value should be. It can be
a problem if one clang version writes a .pcm file and another version reads it
because we can change if an attribute is hashable over time. But as far as I
know, we don't support such cross-version scenario already.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D138859/new/
https://reviews.llvm.org/D138859
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