[PATCH/RFC] fold zext(setcc) into a larger setcc

[Fiona Glaser]

On an out-of-tree target, IR similar to the attached causes the emission of the following instructions (pseudocode):

setcc dst16, cc
zext dst32, dst16

The attached patch fixes it to be the expected:

setcc dst32, cc

because the out-of-tree target supports 32-bit setcc.

But when testing on x86, this crashes with the assertion “Assertion failed: (((!Subtarget->hasAVX512() && VT == MVT::i8) || (VT == MVT::i1)) && "SetCC type must be 8-bit or 1-bit integer”)”. If I remove the !LegalTypes condition, it works fine, but this means that canonicalizing to a non-legal type prior to type legalization is somehow breaking x86.

Does anyone have any idea what’s going on here, or if I’m just approaching this entirely wrong?

Fiona




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