> This patch fixes the specific problem in the test case by skipping over
> equivalences that would rewrite to exactly the same expression as on the
> current iteration. But, it's not clear that there can't also be cycles
> of length > 1. I don't see much point in getting fancy here (I assume
> that if this were a common problem it would have been reported and fixed
> long before now) so I just added a simple limit on the number of
> iterations to be sure the outer loop always terminates.
Sure, but we don't like arbitrary numbers in the compiler like
+ int maxiter = 16;
and adding a --param for it would be overkill, so let's drop the cap.
> 2011-12-12 Sandra Loosemore <san...@codesourcery.com>
> Tom de Vries <t...@codesourcery.com>
>
> gcc/
> * cse.c (find_comparison_args): Add cap on number of iterations
> to avoid infinite loop in case of cycles. Avoid obvious case
> that would result in a circular rewrite.
OK everywhere without the cap and with the same test on ARG2:
/* If it's the same comparison we're already looking at, skip it. */
if (COMPARISON_P (p->exp)
&& XEXP (p->exp, 0) == arg1
&& XEXP (p->exp, 1) == arg2)
continue;
One could imagine a zero being loaded in a register and ARG1 compared with the
register earlier.
> gcc/testsuite/
> * gcc.dg/cse-bug.c: New testcase.
If a testcase doesn't need fancy options, it must go in gcc.c-torture/compile.
--
Eric Botcazou
