PATCH combine.c bug: Bad to transform (cmpop (minus A B) 0) into (cmpop A B).

[Jeffrey A Law]

  In message < 200004041430.QAA29260@ignucius.axis.se >you write:
  > >   > 	* combine.c (simplify_comparison) [MINUS]: Do not replace
  > >   > 	all (op (minus A B) 0) with (op A B).
  > > This might be too pessimistic -- shouldn't we allow this transformation
  > > for any OP that doesn't depend on overflow?  That would be EQ, NE, GEU, G
  > TU,
  > > LEU, and LTU?
  > 
  > As I mentioned, equality comparisons (EQ, NE) are handled by the
  > code after this deleted code.  Since you brought it up, I
  > thought I should check that the trivial transformations to
  > equality comparisons were performed for the unsigned
  > comparisons.  To test, I used the (now committed) test case,
  > tweaked the type of the operands and the comparison operator and
  > checked what landed in simplify_comparison.  It seems the right
  > conversions were done:
Thanks for doing this investigation.  Your patch is fine with or
without the additional comments.

jeff