[PATCH] Avoid useless work in loop vectorization

[Richard Biener]

On Wed, 18 Nov 2015, Alan Lawrence wrote:

> On 13/11/15 08:41, Richard Biener wrote:
> > 
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> > 
> > Richard.
> > 
> > 2015-11-13  Richard Biener  <rguenther@suse.de>
> > 
> > 	* tree-vect-loop.c (vect_analyze_loop_2): Add fatal parameter.
> > 	Signal fatal failure if early checks fail.
> > 	(vect_analyze_loop): If vect_analyze_loop_2 fails fatally
> > 	do not bother testing further vector sizes.
> 
> It seems that on AArch64 this causes:
> 
> FAIL: gcc.dg/vect/vect-outer-1-big-array.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1-big-array.c scan-tree-dump-times vect "grouped
> access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1.c -flto -ffat-lto-objects  scan-tree-dump-times
> vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1.c scan-tree-dump-times vect "grouped access in
> outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1a-big-array.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1a-big-array.c scan-tree-dump-times vect "grouped
> access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1a.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1a.c scan-tree-dump-times vect "grouped access in
> outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1b-big-array.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1b-big-array.c scan-tree-dump-times vect "grouped
> access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1b.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-1b.c scan-tree-dump-times vect "grouped access in
> outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-2b.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-2b.c scan-tree-dump-times vect "grouped access in
> outer loop" 2
> FAIL: gcc.dg/vect/vect-outer-3b.c -flto -ffat-lto-objects
> scan-tree-dump-times vect "grouped access in outer loop" 4
> FAIL: gcc.dg/vect/vect-outer-3b.c scan-tree-dump-times vect "grouped access in
> outer loop" 4
> 
> Still there on r230556, I haven't dug any further yet.

Probably a testsuite issue as we have

/* { dg-final { scan-tree-dump-times "grouped access in outer loop" 1 
"vect" { target { ! vect_multiple_sizes } } } } */
/* { dg-final { scan-tree-dump-times "grouped access in outer loop" 2 
"vect" { target vect_multiple_sizes } } } */

and now possibly terminate early before considering the other vector
size(s).

Richard.