On Wed, Jun 26, 2019 at 10:17:26AM +0200, Uros Bizjak wrote:
> Please note that the patch regresses
>
> FAIL: gcc.target/i386/sse2-vect-simd-11.c scan-tree-dump-times vect
> "vectorized [1-3] loops" 2
> FAIL: gcc.target/i386/sse2-vect-simd-15.c scan-tree-dump-times vect
> "vectorized [1-3] loops" 2
>
> For some reason, the compiler decides to vectorize with 8-byte
> vectors, resulting in:
>
> missed: not vectorized: relevant stmt not supported: _8 = (short
> unsigned int) _4;
> missed: bad operation or unsupported loop bound.
> missed: couldn't vectorize loop
>
> However, the unpatched compiler is able to vectorize loop using
> 16-byte vectors. It looks that the compiler should re-run
> vectorization with wider vectors, if vectorization with narrower
> vectors fails. Jakub, Richard, do you have any insight in this issue?
>
> 2019-06-26 Uroš Bizjak <ubiz...@gmail.com>
>
> * config/i386/i386.c (ix86_autovectorize_vector_sizes):
> Autovectorize 8-byte vectors for TARGET_MMX_WITH_SSE.
The patch isn't correct if TARGET_MMX_WITH_SSE, but not TARGET_AVX, because
in that case it will push only that 8 and nothing else, while you really
want to have 16 and 8 in that order, so that it tries to vectorize first
with 16-byte vectors and fall back to 8-byte. The hook is supposed to
either push nothing at all, then only one vector size is tried,
one derived from preferred_simd_mode, or push all possible vectorization
sizes to be tried.
The following patch fixes the failures:
--- gcc/config/i386/i386.c.jj 2019-06-26 09:15:53.474869259 +0200
+++ gcc/config/i386/i386.c 2019-06-26 10:42:01.354106012 +0200
@@ -21401,6 +21401,11 @@ ix86_autovectorize_vector_sizes (vector_
sizes->safe_push (16);
sizes->safe_push (32);
}
+ else if (TARGET_MMX_WITH_SSE)
+ sizes->safe_push (16);
+
+ if (TARGET_MMX_WITH_SSE)
+ sizes->safe_push (8);
}
/* Implemenation of targetm.vectorize.get_mask_mode. */
Jakub
