Re: [PATCH] simplify-rtx: Fix up SUBREG_PROMOTED_SET arguments [PR104839]

[Richard Biener <rguenther@suse.de>]

On Tue, 8 Mar 2022, Jakub Jelinek wrote:

> Hi!
> 
> The following testcase is miscompiled on powerpc64le-linux at -O1 and higher
> (except for -Og).  The bug was introduced in r12-3252-gcad36f38576a6a7
> which for SIGN_EXTEND from SUBREG_PROMOTED_SIGNED_P SUBREG used
> SUBREG_PROMOTED_SET (temp, 1) (but that makes temp
> SUBREG_PROMOTED_UNSIGNED_P because SRP_UNSIGNED is 1) and similarly the
> ZERO_EXTEND from SUBREG_PROMOTED_UNSIGNED_P SUBREG used
> SUBREG_PROMOTED_SET (temp, 0) (but that makes temp
> SUBREG_PROMOTED_SIGNED_P because SRP_SIGNED is 0).
> The following patch fixes that (swaps the 0s and 1s), but for better
> readability uses the SRP_* constants.
> rtl.h has:
> /* Valid for subregs which are SUBREG_PROMOTED_VAR_P().  In that case
>    this gives the necessary extensions:
>    0  - signed (SPR_SIGNED)
>    1  - normal unsigned (SPR_UNSIGNED)
>    2  - value is both sign and unsign extended for mode
>         (SPR_SIGNED_AND_UNSIGNED).
>    -1 - pointer unsigned, which most often can be handled like unsigned
>         extension, except for generating instructions where we need to
>         emit special code (ptr_extend insns) on some architectures
>         (SPR_POINTER). */
> The expr.c change in the same commit looks ok to me (passes unsignedp
> to SUBREG_PROMOTED_SET, so 0 for signed, 1 for unsigned).
> 
> Starting bootstrap/regtest on powerpc64{,le}-linux now, ok for trunk?

OK.

> 2022-03-08  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR rtl-optimization/104839
> 	* simplify-rtx.cc (simplify_unary_operation_1) <case SIGN_EXTEND>:
> 	Use SRP_SIGNED instead of incorrect 1 in SUBREG_PROMOTED_SET.
> 	(simplify_unary_operation_1) <case ZERO_EXTEND>: Use SRP_UNSIGNED
> 	instead of incorrect 0 in SUBREG_PROMOTED_SET.
> 
> 	* gcc.c-torture/execute/pr104839.c: New test.
> 
> --- gcc/simplify-rtx.cc.jj	2022-02-23 09:17:04.000000000 +0100
> +++ gcc/simplify-rtx.cc	2022-03-08 16:31:20.823246404 +0100
> @@ -1527,7 +1527,7 @@ simplify_context::simplify_unary_operati
>  		  if (partial_subreg_p (temp))
>  		    {
>  		      SUBREG_PROMOTED_VAR_P (temp) = 1;
> -		      SUBREG_PROMOTED_SET (temp, 1);
> +		      SUBREG_PROMOTED_SET (temp, SRP_SIGNED);
>  		    }
>  		  return temp;
>  		}
> @@ -1662,7 +1662,7 @@ simplify_context::simplify_unary_operati
>  		  if (partial_subreg_p (temp))
>  		    {
>  		      SUBREG_PROMOTED_VAR_P (temp) = 1;
> -		      SUBREG_PROMOTED_SET (temp, 0);
> +		      SUBREG_PROMOTED_SET (temp, SRP_UNSIGNED);
>  		    }
>  		  return temp;
>  		}
> --- gcc/testsuite/gcc.c-torture/execute/pr104839.c.jj	2022-03-08 16:46:51.418440078 +0100
> +++ gcc/testsuite/gcc.c-torture/execute/pr104839.c	2022-03-08 16:46:27.044774203 +0100
> @@ -0,0 +1,37 @@
> +/* PR rtl-optimization/104839 */
> +
> +__attribute__((noipa)) short
> +foo (void)
> +{
> +  return -1;
> +}
> +
> +__attribute__((noipa)) int
> +bar (void)
> +{
> +  short i = foo ();
> +  if (i == -2)
> +    return 2;
> +  long k = i;
> +  int j = -1;
> +  volatile long s = 300;
> +  if (k < 0)
> +    {
> +      k += s;
> +      if (k < 0)
> +	j = 0;
> +    }
> +  else if (k >= s)
> +    j = 0;
> +  if (j != -1)
> +    return 1;
> +  return 0;
> +}
> +
> +int
> +main ()
> +{
> +  if (bar () != 0)
> +    __builtin_abort ();
> +  return 0;
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)