[PATCH] If !-prefer-avx128, prefer using even 32-byte integer vector modes

[Jakub Jelinek]

Hi!

Working virtually out of Pago Pago.

Is there a reason why we don't prefer 32-byte integer vector modes
even for AVX?  If a vectorized loop needs some operation that is only
supported by AVX2 we would retry whenever seeing such stmt, so
what I think this costs us mainly some small amount of time
during vectorization analysis.  Examples of functions that can
be vectorized with this patch using 32-byte vectors (and the runtime
of the testcase decreased from ~ 0m2.876s to ~ 0m2.258s).

#define N 1024
int a[N], b[N];
float c[N];

__attribute__((noinline, noclone)) void
f1 ()
{
  int i;
  for (i = 0; i < N; i++)
    a[i] = b[i];
}

__attribute__((noinline, noclone)) void
f2 ()
{
  a[0] = b[0];
  a[1] = b[1];
  a[2] = b[2];
  a[3] = b[3];
  a[4] = b[4];
  a[5] = b[5];
  a[6] = b[6];
  a[7] = b[7];
}

__attribute__((noinline, noclone)) void
f3 ()
{
  int i;
  for (i = 0; i < N; i++)
    c[i] = a[i];
}

__attribute__((noinline, noclone)) void
f4 ()
{
  int i;
  for (i = 0; i < N; i++)
    a[i] = 19;
}

int
main ()
{
  int i;
  for (i = 0; i < N; i++)
    b[i] = i;
  for (i = 0; i < 10000000; i++)
    {
      f1 ();
      f2 ();
      f3 ();
      f4 ();
    }
  return 0;
}


2011-11-08  Jakub Jelinek  <ja...@redhat.com>

        * config/i386/i386.c (ix86_preferred_simd_mode): Even for TARGET_AVX
        if not TARGET_PREFER_AVX128 return 32-byte SI/DI vectors.

--- gcc/config/i386/i386.c.jj   2011-11-07 08:32:09.000000000 -1100
+++ gcc/config/i386/i386.c      2011-11-07 19:19:57.000000000 -1100
@@ -37881,9 +37881,9 @@ ix86_preferred_simd_mode (enum machine_m
     case HImode:
       return TARGET_AVX2 ? V16HImode : V8HImode;
     case SImode:
-      return TARGET_AVX2 ? V8SImode : V4SImode;
+      return (TARGET_AVX && !TARGET_PREFER_AVX128) ? V8SImode : V4SImode;
     case DImode:
-      return TARGET_AVX2 ? V4DImode : V2DImode;
+      return (TARGET_AVX && !TARGET_PREFER_AVX128) ? V4DImode : V2DImode;
 
     case SFmode:
       if (TARGET_AVX && !TARGET_PREFER_AVX128)

        Jakub