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Re: [PATCH] Fix up ix86_expand_set_or_movmem (PR target/61060)


> Hi!
> 
> As discussed in the PR, ix86_expand_set_or_movmem assumes that count == 0
> means !CONST_INT_P (count_exp), but that is not necessarily true with
> -O0 -ftree-ter, when the middle-end doesn't immediately see the length
> argument be integer_zerop, yet TER results in it being expanded as
> const0_rtx.
> 
> There is nothing to set or move in that case, so this patch makes the
> backend more tolerand just by returning true immediately.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK,
Honza
> 
> 2014-05-12  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR target/61060
> 	* config/i386/i386.c (ix86_expand_set_or_movmem): If count_exp
> 	is const0_rtx, return immediately.  Don't test count == 0 when
> 	it is always true.
> 
> 	* gcc.dg/pr61060.c: New test.
> 
> --- gcc/config/i386/i386.c.jj	2014-05-11 22:21:28.000000000 +0200
> +++ gcc/config/i386/i386.c	2014-05-12 10:59:18.940416162 +0200
> @@ -24156,8 +24156,13 @@ ix86_expand_set_or_movmem (rtx dst, rtx
>      align = MEM_ALIGN (dst) / BITS_PER_UNIT;
>  
>    if (CONST_INT_P (count_exp))
> -    min_size = max_size = probable_max_size = count = expected_size
> -      = INTVAL (count_exp);
> +    {
> +      min_size = max_size = probable_max_size = count = expected_size
> +	= INTVAL (count_exp);
> +      /* When COUNT is 0, there is nothing to do.  */
> +      if (!count)
> +	return true;
> +    }
>    else
>      {
>        if (min_size_exp)
> @@ -24166,7 +24171,7 @@ ix86_expand_set_or_movmem (rtx dst, rtx
>  	max_size = INTVAL (max_size_exp);
>        if (probable_max_size_exp)
>  	probable_max_size = INTVAL (probable_max_size_exp);
> -      if (CONST_INT_P (expected_size_exp) && count == 0)
> +      if (CONST_INT_P (expected_size_exp))
>  	expected_size = INTVAL (expected_size_exp);
>       }
>  
> --- gcc/testsuite/gcc.dg/pr61060.c.jj	2014-05-12 11:03:10.797222337 +0200
> +++ gcc/testsuite/gcc.dg/pr61060.c	2014-05-12 11:03:02.882263281 +0200
> @@ -0,0 +1,19 @@
> +/* PR target/61060 */
> +/* { dg-do compile } */
> +/* { dg-options "-O0 -ftree-ter" } */
> +
> +typedef __SIZE_TYPE__ size_t;
> +
> +extern inline __attribute__ ((gnu_inline, always_inline, artificial))
> +void *memset (void *dest, int ch, size_t len)
> +{
> +  return __builtin_memset (dest, ch, len);
> +}
> +
> +char buf[10];
> +
> +void
> +foo (void)
> +{
> +  memset (buf, sizeof (buf), 0);
> +}
> 
> 	Jakub


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