[Bug target/69810] PowerPC64: unrecognizable insn

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69810

--- Comment #7 from David Edelsohn <dje at gcc dot gnu.org> ---
Created attachment 37755
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37755&action=edit
extqihi patch

Because this idiom occurs so rarely (like never, except for an artificial
csmith testcase :-), the easiest solution that preserves the optimization seems
to be a patch that changes the splitter to a normal combiner pattern and emits
the extend and compare instructions as a single output template.  The operand
is correctly sign-extended to SImode, the "HImode" temporary holds an SImode
value, and the compare instruction can use the "HImode" value as input, but it
is difficult to represent this in a pattern.  So punt.