On Sat, 14 Mar 2020, Jakub Jelinek wrote:
> Hi!
>
> On the following testcase, if there is ASLR, the compiler generates
> different code each time (out of 1000 invocations 994 unique assembler
> contents). The problem is that undistribute_bitref_for_vector uses
> a hash_map from a tree (SSA_NAME) to a vector and such a hash_map is
> by default doing pointer hashing on the SSA_NAME rather than using
> something stable (SSA_NAME_VERSION).
> One possible way would be to use SSA_NAME_VERSION as hash function,
> but given that we from the hash_map traversal just populate a vector
> which is then sorted, I think it is easier to make the sort callback
> use SSA_NAME_VERSION as secondary sorting key and thus ensure stable
> sort (that is generally desirable anyway).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2020-03-14 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94166
> * tree-ssa-reassoc.c (sort_by_mach_mode): Use SSA_NAME_VERSION
> as secondary comparison key.
>
> * gcc.dg/pr94166.c: New test.
>
> --- gcc/tree-ssa-reassoc.c.jj 2020-01-12 11:54:38.510381771 +0100
> +++ gcc/tree-ssa-reassoc.c 2020-03-13 14:06:32.358085863 +0100
> @@ -1793,8 +1793,11 @@ sort_by_mach_mode (const void *p_i, cons
> return 1;
> else if (mode1 < mode2)
> return -1;
> - else
> - return 0;
> + if (SSA_NAME_VERSION (tr1) < SSA_NAME_VERSION (tr2))
> + return -1;
> + else if (SSA_NAME_VERSION (tr1) > SSA_NAME_VERSION (tr2))
> + return 1;
> + return 0;
> }
>
> /* Cleanup hash map for VECTOR information. */
> --- gcc/testsuite/gcc.dg/pr94166.c.jj 2020-03-13 14:36:46.382260562 +0100
> +++ gcc/testsuite/gcc.dg/pr94166.c 2020-03-13 14:40:32.536916640 +0100
> @@ -0,0 +1,24 @@
> +/* PR tree-optimization/94166 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fcompare-debug" } */
> +
> +typedef int __m128i __attribute__((__may_alias__, __vector_size__(4 * sizeof
> (int))));
> +unsigned int b[512];
> +
> +void
> +foo (unsigned int *x, __m128i *y)
> +{
> +#define A(n) __m128i v##n = y[n];
> +#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n##7)
> \
> + A(n##8) A(n##9) A(n##a) A(n##b) A(n##c) A(n##d) A(n##e) A(n##f)
> +#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n##7)
> + C(0x)
> +#undef A
> +#define A(n) *(__m128i *) &b[4 * n] = v##n;
> + C(0x)
> +#undef A
> +#define A(n) + b[4 * n] + b[4 * n + 1] + b[4 * n + 2] + b[4 * n + 3]
> + *x = *x
> + C(0x)
> + ;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
