Re: [PATCH] Improve MIN_EXPR/MAX_EXPR constant folding

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On Jan 14, 2006, at 6:01 AM, Eric Botcazou wrote:

> Hi,
>
> The attached Ada testcase triggers an ICE in the gimplifier
>
> eric@linux:~/build/gcc/native> gcc/xgcc -Bgcc -S bug_list.adb
> +===========================GNAT BUG 
> DETECTED==============================+
> | 4.2.0 20060108 (experimental) (x86_64-suse-linux-gnu) GCC error:     
>     |
> | in create_tmp_var, at gimplify.c:410                                 
>     |
> | Error detected at bug_list.adb:9:8
>
> because the compiler is trying to create a temporary with a 
> variable-sized
> type.  It turns out that the type actually has a fixed size, but the
> expression of the size is of the form:
>
> The calculation's type is signed (long int sizetype) so the compiler 
> cannot
> constant-fold the tree to 4.  The proposed fix is to teach fold how to
> simplify MIN (MAX (arg, val), val) and its sibling expression.
>
> Bootstrapped/regtested on x86_64-linux-gnu.  OK for mainline?

I would add some C testcases.
Like:
/* { dg-do compile } */
/* { dg-options "-O1 -fdump-tree-optimized" } */

int f(int a, int c)
{
  return (a > c?a:c)>c?c:(a > c?a:c);
}

/* { dg-final { scan-tree-dump-times "MIN_EXPR" 0 "optimized"} } */
/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "optimized"} } */
/* { dg-final { cleanup-tree-dump "optimized" } } */
----------------------------------------
/* { dg-do compile } */
/* { dg-options "-O1 -fdump-tree-optimized" } */

int f(int a, int c)
{
  return c<(a < c?a:c)?(a < c?a:c):c;
}

/* { dg-final { scan-tree-dump-times "MIN_EXPR" 0 "optimized"} } */
/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "optimized"} } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

This should simplify now as we get in fold "MIN_EXPR <MAX_EXPR <c, a>, 
c>;" and
"MAX_EXPR <MIN_EXPR <c, a>, c>".  Oh, I see you are comparing only 
constants, I think
that is wrong as shown by my example.

-- Pinski