svenvh added inline comments.
================
Comment at: clang/lib/CodeGen/CGExprScalar.cpp:4789
-
- if (!CGF.CGM.getCodeGenOpts().PreserveVec3Type) {
- Src = createCastsForTypeOfSameSize(Builder, CGF.CGM.getDataLayout(), Src,
----------------
Anastasia wrote:
> While I agree with this fix and it obviously looks incorrect, I wonder if the
> original intent was to condition the previous statement instead so that we
> avoid converting to size 4 at all? Although I have a feeling we are entering
> the behavior that is not documented anywhere. In the spec I can see this:
>
>
> ```
> When the operand and result type contain a different number of elements, the
> result shall be implementation-defined except if the operand is a 4-component
> vector and the result is a 3-component vector. In this case, the bits in the
> operand shall be returned directly without modification as the new type.
> ```
>
> but it seems to cover the inverse conversion?
Yeah I have a similar fix for the inverse case (which is further down in this
function) in my local branch.
I did try to extend the guard to also cover the `ConvertVec3AndVec4` call, but
that also led to invalid StoreInst creation. Since I wasn't sure about the
intent of the conditioning on `PreserveVec3Type` here, I didn't investigate
further.
I was hoping @jaykang10 (who added this in D30810) might have some insight into
why the guard was here in the first place. But it has been over 4 years since
that was committed, so there might not be a ready answer. Either way, I'll
hold off committing this for a few more days.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D107963/new/
https://reviews.llvm.org/D107963
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
