[Bug tree-optimization/65930] Reduction with sign-change not handled

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65930

--- Comment #23 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Rainer Orth from comment #21)
> (In reply to Richard Biener from comment #19)
> > Author: rguenth
> > Date: Wed Oct 23 12:41:49 2019
> > New Revision: 277322
> > 
> > URL: https://gcc.gnu.org/viewcvs?rev=277322&root=gcc&view=rev
> > Log:
> > 2019-10-23  Richard Biener  <rguenther@suse.de>
> > 
> > 	PR tree-optimization/65930
> > 	* tree-vect-loop.c (check_reduction_path): Allow conversions
> > 	that only change the sign.
> > 	(vectorizable_reduction): Relax latch def stmts we handle further.
> > 
> > 	* gcc.dg/vect/vect-reduc-2char-big-array.c: Adjust.
> > 	* gcc.dg/vect/vect-reduc-2char.c: Likewise.
> > 	* gcc.dg/vect/vect-reduc-2short.c: Likewise.
> > 	* gcc.dg/vect/vect-reduc-dot-s8b.c: Likewise.
> > 	* gcc.dg/vect/vect-reduc-pattern-2c.c: Likewise.
> 
> This patch caused a couple of regressions on Solaris/SPARC (32 and 64-bit):
> 
> +FAIL: gcc.dg/vect/vect-reduc-2char-big-array.c -flto -ffat-lto-objects 
> scan-tree-dump-times vect "vectorized 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-2char-big-array.c scan-tree-dump-times vect
> "vectorized 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-2char.c -flto -ffat-lto-objects 
> scan-tree-dump-times vect "vectorized 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-2char.c scan-tree-dump-times vect "vectorized
> 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-2short.c -flto -ffat-lto-objects 
> scan-tree-dump-times vect "vectorized 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-2short.c scan-tree-dump-times vect "vectorized
> 3 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-dot-s8b.c -flto -ffat-lto-objects 
> scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-dot-s8b.c scan-tree-dump-times vect
> "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-pattern-2c.c -flto -ffat-lto-objects 
> scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-reduc-pattern-2c.c scan-tree-dump-times vect
> "vectorized 1 loops" 1
> 
> I'm attaching the vect-reduc-2char-big-array.c dump as an example.

OK, there's

/vol/gcc/src/hg/trunk/local/gcc/testsuite/gcc.dg/vect/vect-reduc-2char-big-array.c:44:9:
missed:   not vectorized: relevant stmt not supported: min_47 = MIN_EXPR <_20,
min_88>;

looks like those XFAILs are not expected to pass within the constraints
of the testcases (guess that was to be expected).  There's vect_no_int_min_max
to cover up I guess.

For vect-reduc-dot-s8b.c I wonder why it detected the widen_mult pattern
but failed vectorization (dump file?)  Otherwise there's
vect_widen_mult_qi_to_hi which sparc doesn't have.  At least that was used
in the vect-reduc-pattern-2c.c case.

I'm going to install a patch.