[PATCH] Optimize %k register comparison against zero (PR target/82855)

[Jakub Jelinek]

Hi!

Without the following patch we emit kmovb %k1, %eax; testb %al, %al
when if just testing the Zero bit we can as well do ktestb %k1, %k1.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-11-06  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  2017-10-28 09:00:44.000000000 +0200
+++ gcc/config/i386/i386.md     2017-11-06 12:57:44.171215745 +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>,k,?m<r>")
+                (match_operand:SWI1248_AVX512BWDQ2_64 1 "const0_operand")))]
+  "ix86_match_ccmode (insn, CCZmode)"
+  "@
+   test{<imodesuffix>}\t%0, %0
+   ktest<mskmodesuffix>\t%0, %0
+   cmp{<imodesuffix>}\t{%1, %0|%0, %1}"
+  [(set_attr "type" "test,msklog,icmp")
+   (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 2017-11-06 
13:51:21.380463119 +0100
+++ gcc/testsuite/gcc.target/i386/avx512dq-pr82855.c    2017-11-06 
13:52:07.164875064 +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