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* [Bug tree-optimization/61299] New: [4.9 Regression] Performance regression for the SIMD rotate operation with GCC vector extensions
@ 2014-05-24  1:24 siarhei.siamashka at gmail dot com
  2014-05-24  8:35 ` [Bug tree-optimization/61299] [4.9/4.10 " glisse at gcc dot gnu.org
                   ` (4 more replies)
  0 siblings, 5 replies; 6+ messages in thread
From: siarhei.siamashka at gmail dot com @ 2014-05-24  1:24 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61299

            Bug ID: 61299
           Summary: [4.9 Regression] Performance regression for the SIMD
                    rotate operation with GCC vector extensions
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: siarhei.siamashka at gmail dot com

A small test:

/**************/
typedef unsigned int uint32x4 __attribute__ ((vector_size(16)));
typedef struct { uint32x4 a, b; } prng_t;
void foo(prng_t *x)
{
        x->a ^= ((x->b << 17) ^ (x->b >> (32 - 17)));
}
/**************/

Gets compiled into the following slow code with GCC 4.9 (CFLAGS="-O3"):

0000000000000000 <foo>:
   0:   66 0f 6f 47 10          movdqa 0x10(%rdi),%xmm0
   5:   66 0f 70 c8 55          pshufd $0x55,%xmm0,%xmm1
   a:   66 0f 7e c0             movd   %xmm0,%eax
   e:   c1 c8 0f                ror    $0xf,%eax
  11:   89 44 24 e8             mov    %eax,-0x18(%rsp)
  15:   66 0f 7e c8             movd   %xmm1,%eax
  19:   66 0f 6f c8             movdqa %xmm0,%xmm1
  1d:   c1 c8 0f                ror    $0xf,%eax
  20:   66 0f 6a c8             punpckhdq %xmm0,%xmm1
  24:   89 44 24 ec             mov    %eax,-0x14(%rsp)
  28:   66 0f 70 c0 ff          pshufd $0xff,%xmm0,%xmm0
  2d:   66 0f 6e 5c 24 ec       movd   -0x14(%rsp),%xmm3
  33:   66 0f 7e c8             movd   %xmm1,%eax
  37:   c1 c8 0f                ror    $0xf,%eax
  3a:   89 44 24 f0             mov    %eax,-0x10(%rsp)
  3e:   66 0f 7e c0             movd   %xmm0,%eax
  42:   66 0f 6e 44 24 e8       movd   -0x18(%rsp),%xmm0
  48:   66 0f 6e 4c 24 f0       movd   -0x10(%rsp),%xmm1
  4e:   c1 c8 0f                ror    $0xf,%eax
  51:   66 0f 62 c3             punpckldq %xmm3,%xmm0
  55:   89 44 24 f4             mov    %eax,-0xc(%rsp)
  59:   66 0f 6e 54 24 f4       movd   -0xc(%rsp),%xmm2
  5f:   66 0f 62 ca             punpckldq %xmm2,%xmm1
  63:   66 0f 6c c1             punpcklqdq %xmm1,%xmm0
  67:   66 0f ef 07             pxor   (%rdi),%xmm0
  6b:   0f 29 07                movaps %xmm0,(%rdi)
  6e:   c3                      retq   

It used to be a lot better with GCC 4.8 (CFLAGS="-O3"):

0000000000000000 <foo>:
   0:   66 0f 6f 4f 10          movdqa 0x10(%rdi),%xmm1
   5:   66 0f 6f c1             movdqa %xmm1,%xmm0
   9:   66 0f 72 d1 0f          psrld  $0xf,%xmm1
   e:   66 0f 72 f0 11          pslld  $0x11,%xmm0
  13:   66 0f ef c1             pxor   %xmm1,%xmm0
  17:   66 0f ef 07             pxor   (%rdi),%xmm0
  1b:   66 0f 7f 07             movdqa %xmm0,(%rdi)
  1f:   c3                      retq


^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-06-30 16:58 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-05-24  1:24 [Bug tree-optimization/61299] New: [4.9 Regression] Performance regression for the SIMD rotate operation with GCC vector extensions siarhei.siamashka at gmail dot com
2014-05-24  8:35 ` [Bug tree-optimization/61299] [4.9/4.10 " glisse at gcc dot gnu.org
2014-05-24  8:54 ` siarhei.siamashka at gmail dot com
2014-06-27  7:04 ` jakub at gcc dot gnu.org
2014-06-30 16:56 ` jakub at gcc dot gnu.org
2014-06-30 16:58 ` jakub at gcc dot gnu.org

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