On Wed, 23 Feb 2022, Jakub Jelinek wrote:
> Hi!
>
> The following patch avoids infinite recursion during generic folding.
> The (cmp (bswap @0) INTEGER_CST@1) simplification relies on
> (bswap @1) actually being simplified, if it is not simplified, we just
> move the bswap from one operand to the other and if @0 is also INTEGER_CST,
> we apply the same rule next.
>
> The reason why bswap @1 isn't folded to INTEGER_CST is that the INTEGER_CST
> has TREE_OVERFLOW set on it and fold-const-call.cc predicate punts in
> such cases:
> static inline bool
> integer_cst_p (tree t)
> {
> return TREE_CODE (t) == INTEGER_CST && !TREE_OVERFLOW (t);
> }
> The patch uses ! modifier to ensure the bswap is simplified, but because
> ! is only supported in gimple-match, guards it also with #if GIMPLE.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Does it recurse on GIMPLE as well? If not, the ! is not necessary
since you guard with GIMPLE already (but it deserves a comment I guess).
> 2022-02-22 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/104644
> * match.pd (cmp (bswap @0) INTEGER_CST@1): Restrict optimization to
> GIMPLE only and use ! modifier on bswap.
>
> * gcc.dg/pr104644.c: New test.
>
> --- gcc/match.pd.jj 2022-02-18 12:38:06.075393091 +0100
> +++ gcc/match.pd 2022-02-22 20:22:02.222022022 +0100
> @@ -3959,10 +3959,13 @@ (define_operator_list SYNC_FETCH_AND_AND
> (cmp (bswap@2 @0) (bswap @1))
> (with { tree ctype = TREE_TYPE (@2); }
> (cmp (convert:ctype @0) (convert:ctype @1))))
> +#if GIMPLE
> (simplify
> (cmp (bswap @0) INTEGER_CST@1)
> (with { tree ctype = TREE_TYPE (@1); }
> - (cmp (convert:ctype @0) (bswap @1)))))
> + (cmp (convert:ctype @0) (bswap! @1))))
> +#endif
> + )
> /* (bswap(x) >> C1) & C2 can sometimes be simplified to (x >> C3) & C2. */
> (simplify
> (bit_and (convert1? (rshift@0 (convert2? (bswap@4 @1)) INTEGER_CST@2))
> --- gcc/testsuite/gcc.dg/pr104644.c.jj 2022-02-22 20:02:32.020408468
> +0100
> +++ gcc/testsuite/gcc.dg/pr104644.c 2022-02-22 20:02:04.609785996 +0100
> @@ -0,0 +1,9 @@
> +/* PR tree-optimization/104644 */
> +/* { dg-do compile } */
> +/* { dg-options "-Wno-overflow" } */
> +
> +int
> +foo (void)
> +{
> + return __builtin_bswap16 (1.31072e+5f) != (signed char) 1.31072e+5f;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
