================
@@ -1191,12 +1191,17 @@ Value *CodeGenFunction::EmitCommonNeonBuiltinExpr(
return Builder.CreateBitCast(Ops[0], Ty);
}
case NEON::BI__builtin_neon_vaddhn_v: {
+ // SrcTy has double-width elements (e.g. <8 x i16> when VTy is <8 x i8>).
llvm::FixedVectorType *SrcTy =
llvm::FixedVectorType::getExtendedElementVectorType(VTy);
- // %sum = add <4 x i32> %lhs, %rhs
+ // Example: vaddhn_s16(int16x8_t, int16x8_t)
+ // Ops are <16 x i8>, SrcTy is <8 x i16> -> mismatch
----------------
E00N777 wrote:
> > Note that for vaddhn_s16(int16x8_t, int16x8_t), the Ops are actually <8 x
> > i16> ;-) Then, since vaddhn_s16 expands to: `__ret = (int8x8_t)
> > __builtin_neon_vaddhn_v((int8x16_t)__p0, (int8x16_t)__p1, 0);` the
> > arguments to __builtin_neon_vaddhn_v are indeed <16 x i8>. It's a subtle
> > and a tricky thing to document. It might be easier to skip the comment.
>
> Thank you! That's a good point! I agree that trying to explain <8 x i16> ->
> <16 x i8> is quite confusing 😄 I've removed the comments in ARM.cpp
>
> > OK, could you try using deriveNeonSISDIntrinsicOperandTypes (or something
> > similar) instead? Basically, we want the code to be shared.
> > EDIT Btw, it's no problem if there's no easy solution here!
>
> Thank you for the suggestion! I gave `deriveNeonSISDIntrinsicOperandTypes` a
> try, but it didn't work for `vraddhn`. It's because the function gets the
> argument types from the operands, but `vraddhn` has already changed <8 x i16>
> to <16 x i8>, so we can't get <8 x i16> back.
>
> So I tried to create a helper to group `vraddhn` with the above block, but it
> needed a hardcoded `builtinID == vraddhn` to decide to widen the source type
> or not. To keep this clean for future intrinsics, I added a `WidenArgs` flag
> to `AArch64CodeGenUtils.h`. I keep it as a separate commit. Not sure how you
> feel about that approach 😄 For now, we only have 1 intrinsic uses that flag,
> but maybe narrowing-subtraction would use it too (I'm happy to pick it up if
> no one has already on it 😀 )
Feel free to pick `narrowing-subtraction` up, I haven't started this part of
the work yet.
https://github.com/llvm/llvm-project/pull/204989
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