[llvm-dev] how to simplify FP ops with an undef operand?

[Sanjay Patel via llvm-dev]

%y = fadd float %x, undef

Can we simplify this?

Currently in IR, we do nothing for fadd/fsub/fmul. For fdiv/frem, we
propagate undef. The code comment for fdiv/frem says:
"the undef could be a snan"

If that's correct, then shouldn't it be the same for fadd/fsub/fmul? But
this can't be correct because we support targets that don't raise
exceptions...and even targets that raise exceptions do not trap by default
on snan?
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