On Tue, Nov 07, 2017 at 11:21:15AM +0100, Uros Bizjak wrote:
> On Tue, Nov 7, 2017 at 11:10 AM, Jakub Jelinek <ja...@redhat.com> wrote:
>
> >> > Isn't it sufficient that moves disparage slightly the k alternatives?
> >> > Or are you worried about the case where the pseudo would need to be
> >> > spilled
> >> > and LRA would choose to reload it into a %kN register?
> >>
> >> The later... Perhaps it is possible to prevent unwanted reloads with
> >> ?k (or even ??k, we already have ?m<r>, IDK). I have used *k in
> >> zero-extend patterns to prevent unwanted reloads, which is perhaps too
> >> strong, but we have ree pass that eliminates unwanted moves in this
> >> case (*k in move patterns is handled by other regmove elimination
> >> passes).
> >
> > ?k gives the same IRA decisions as *k, in both cases it considers
> > GENERAL_REGS as expensive as MASK_EVEX_REGS and picks up GENERAL_REGS
> > rather than MASK_EVEX_REGS for the pseudo, which results in
> > kmovb %k1, %eax; test.
>
> Can we use some of the new RA modifiers here?
So, for the testcase in question, GENERAL_REGS have cost 2000:
k works (MASK_EVEX_REGS cost 0)
*k doesn't work, IRA chooses GENERAL_REGS (MASK_EVEX_REGS cost 2000)
?k doesn't work, IRA chooses GENERAL_REGS (MASK_EVEX_REGS cost 2000)
!k works (MASK_EVEX_REGS cost 0)
^k doesn't work, IRA chooses GENERAL_REGS (MASK_EVEX_REGS cost 2000)
$k works (MASK_EVEX_REGS cost 0)
> --cut here--
> '?'
> Disparage slightly the alternative that the '?' appears in, as a
> choice when no alternative applies exactly. The compiler regards
> this alternative as one unit more costly for each '?' that appears
> in it.
>
> '!'
> Disparage severely the alternative that the '!' appears in. This
> alternative can still be used if it fits without reloading, but if
> reloading is needed, some other alternative will be used.
>
> '^'
> This constraint is analogous to '?' but it disparages slightly the
> alternative only if the operand with the '^' needs a reload.
>
> '$'
> This constraint is analogous to '!' but it disparages severely the
> alternative only if the operand with the '$' needs a reload.
> --cut here--
>
> '$' looks promising to prevent unwanted reloads to kN register.
So, ok for trunk if it passes bootstrap/regtest?
2017-11-07 Jakub Jelinek <ja...@redhat.com>
PR target/82855
* config/i386/i386.md (SWI1248_AVX512BWDQ2_64): New mode iterator.
(*cmp<mode>_ccz_1): New insn with $k alternative.
* gcc.target/i386/avx512dq-pr82855.c: New test.
--- gcc/config/i386/i386.md.jj 2017-11-06 17:23:10.674996727 +0100
+++ gcc/config/i386/i386.md 2017-11-07 11:44:40.081328781 +0100
@@ -1275,6 +1275,26 @@ (define_expand "cmp<mode>_1"
(compare:CC (match_operand:SWI48 0 "nonimmediate_operand")
(match_operand:SWI48 1 "<general_operand>")))])
+(define_mode_iterator SWI1248_AVX512BWDQ2_64
+ [(QI "TARGET_AVX512DQ") (HI "TARGET_AVX512DQ")
+ (SI "TARGET_AVX512BW") (DI "TARGET_AVX512BW && TARGET_64BIT")])
+
+(define_insn "*cmp<mode>_ccz_1"
+ [(set (reg FLAGS_REG)
+ (compare (match_operand:SWI1248_AVX512BWDQ2_64 0
+ "nonimmediate_operand" "<r>,?m<r>,$k")
+ (match_operand:SWI1248_AVX512BWDQ2_64 1 "const0_operand")))]
+ "ix86_match_ccmode (insn, CCZmode)"
+ "@
+ test{<imodesuffix>}\t%0, %0
+ cmp{<imodesuffix>}\t{%1, %0|%0, %1}
+ ktest<mskmodesuffix>\t%0, %0"
+ [(set_attr "type" "test,icmp,msklog")
+ (set_attr "length_immediate" "0,1,*")
+ (set_attr "modrm_class" "op0,unknown,*")
+ (set_attr "prefix" "*,*,vex")
+ (set_attr "mode" "<MODE>")])
+
(define_insn "*cmp<mode>_ccno_1"
[(set (reg FLAGS_REG)
(compare (match_operand:SWI 0 "nonimmediate_operand" "<r>,?m<r>")
--- gcc/testsuite/gcc.target/i386/avx512dq-pr82855.c.jj 2017-11-07
08:56:02.910321163 +0100
+++ gcc/testsuite/gcc.target/i386/avx512dq-pr82855.c 2017-11-07
08:56:02.910321163 +0100
@@ -0,0 +1,14 @@
+/* PR target/82855 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -mavx512vl -mavx512dq" } */
+/* { dg-final { scan-assembler {\mktestb\M} } } */
+
+#include <immintrin.h>
+
+int
+foo (const __m256i *ptr)
+{
+ __m256i v = _mm256_loadu_si256 (ptr);
+ __mmask8 m = _mm256_cmpeq_epi32_mask (v, _mm256_setzero_si256 ());
+ return 0 == m;
+}
Jakub
