[PATCH] D111523: [AMDGPU] Don't emit 24 bit mul intrinsic for > 32 bit result.

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added a comment.

In D111523#3056031 <https://reviews.llvm.org/D111523#3056031>, @foad wrote:

> In D111523#3055898 <https://reviews.llvm.org/D111523#3055898>, @rampitec wrote:
>
>> There should be nothing wrong with mul24 regardless of the destination type. If a 64 bit mul fits 24 bit it still can use 24 bit mul, just extended to 64 bit.
>
> No, I think this patch makes sense. We were only checking that the inputs fit in 24 bits. A full 24-bit multiply would have a 48 bit result, which you could safely extend to 64 bits. But mul24 gives you a truncated 32-bit result, which you can't safely extend to 64 bits.

Should we check `numBits(LHS) + numBits(RHS) <= DstTy.sizeInBits() || Size <= 32` instead?


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https://reviews.llvm.org/D111523