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Re: [PATCH] Add X != !X pattern
- From: Richard Biener <rguenther at suse dot de>
- To: James Greenhalgh <james dot greenhalgh at arm dot com>
- Cc: Andrew Pinski <pinskia at gmail dot com>, Andreas Schwab <schwab at suse dot de>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 5 Aug 2015 15:45:39 +0200 (CEST)
- Subject: Re: [PATCH] Add X != !X pattern
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot LSU dot 2 dot 11 dot 1508041549270 dot 19642 at zhemvz dot fhfr dot qr> <mvmh9oet5cn dot fsf at hawking dot suse dot de> <alpine dot LSU dot 2 dot 11 dot 1508051213360 dot 19642 at zhemvz dot fhfr dot qr> <CA+=Sn1nSunXx2d_gwNQPY3uLN+QaCj=SoQns9QvZQ3Wf7ur47w at mail dot gmail dot com> <alpine dot LSU dot 2 dot 11 dot 1508051309190 dot 19642 at zhemvz dot fhfr dot qr> <20150805133256 dot GA24020 at arm dot com> <alpine dot LSU dot 2 dot 11 dot 1508051536370 dot 19642 at zhemvz dot fhfr dot qr>
On Wed, 5 Aug 2015, Richard Biener wrote:
> On Wed, 5 Aug 2015, James Greenhalgh wrote:
>
> > On Wed, Aug 05, 2015 at 12:09:35PM +0100, Richard Biener wrote:
> > > On Wed, 5 Aug 2015, Andrew Pinski wrote:
> > >
> > > > On Wed, Aug 5, 2015 at 3:16 AM, Richard Biener <rguenther@suse.de> wrote:
> > > > > On Wed, 5 Aug 2015, Andreas Schwab wrote:
> > > > >
> > > > >> Richard Biener <rguenther@suse.de> writes:
> > > > >>
> > > > >> > * gimple-fold.c (gimple_fold_stmt_to_constant_1): Canonicalize
> > > > >> > bool compares on RHS.
> > > > >> > * match.pd: Add X ==/!= !X is false/true pattern.
> > > > >>
> > > > >> ERROR in VTST/VTSTQ (/opt/gcc/gcc-20150805/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/vtst.c line 97 in buffer 'expected_signed') at type uint8x8 index 1: got 0x1 != 0xff (signed input)
> > > > >> FAIL: gcc.target/aarch64/advsimd-intrinsics/vtst.c -O1 execution test
> > > > >> FAIL: gcc.target/aarch64/simd/int_comparisons_1.c scan-assembler-times [ \t]cmtst[ \t]+v[0-9]+.[0-9]+[bshd],[ \t]*v[0-9]+.[0-9]+[bshd],[ \t]+v[0-9]+.[0-9]+[bshd] 14
> > > > >> FAIL: gcc.target/aarch64/simd/int_comparisons_1.c scan-assembler-times [ \t]cmtst[ \t]+d[0-9]+,[ \t]*d[0-9]+,[ \t]+d[0-9]+ 4
> > > > >> FAIL: gcc.target/aarch64/simd/int_comparisons_2.c execution test
> > > > >> FAIL: gcc.target/aarch64/singleton_intrinsics_1.c scan-assembler-times \\tcmtst\\td[0-9]+, d[0-9]+, d[0-9]+ 2
> > > > >
> > > > > Ick - somebody will have to come up with a reduced testcase for one of
> > > > > this (best an execute fail). Reduced to one failing case so I can
> > > > > investigate with a cross compiler.
> > > > >
> > > > > Eventually smells like a aarch64 vector specific issue or a latent
> > > > > issue with the truth_valued_p predicate for vector types.
> > > >
> > > > Or constant_boolean_node is not returning {-1,-1,-1,-1} for true vectors.
> > >
> > > It does.
> >
> > You could try with the attached (execute) testcase.
> >
> > Output for me (x86_64/AArch64 trunk compiler) is:
> >
> > Expected: 0000ffffffffff00 Got: 00007f80807f8000
> >
> > Those folded values look suspicious! We fold as so:
> >
> > arg1_2 = { -128, -1, 127, -122, -128, -1, 0, 118 };
> > arg2_3 = { 127, -128, 127, -128, -1, 127, 127, 0 };
> >
> > Visiting statement:
> > _5 = arg1_2 & arg2_3;
> > which is likely CONSTANT
> > Match-and-simplified arg1_2 & arg2_3 to { 0, -128, 127, -128, -128, 127, 0, 0 }
> > Lattice value changed to CONSTANT { 0, -128, 127, -128, -128, 127, 0, 0 }. Adding SSA edges to worklist.
> > interesting_ssa_edges: adding SSA use in _13 = VIEW_CONVERT_EXPR<uint8x8_t>(_5);
> > marking stmt to be not simulated again
> >
> > I'd have expected masks of "-1" in the true vector lanes rather than what
> > we end up with.
>
> __extension__ static __inline uint8x8_t __attribute__
> ((__always_inline__))
> vtst_s8 (int8x8_t __a, int8x8_t __b)
> {
> return (uint8x8_t) ((__a & __b) != 0);
> }
>
> you expect that to be a truth and but it is a bitwise and. So IMHO
> it works "as expected". Does the backend actually generate a truth-and
> instruction for vtst_s8!?
>
> Anyway, trying a cross now.
Reproduces on x86_64 as well, fix in testing.
Richard.