Re: [PATCH] powerpc: Fix up *branch_anddi3_dot for -m32 -mpowerpc64 [PR109566]

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Jakub,

Thanks for the prompt fix!

on 2023/4/24 23:54, Jakub Jelinek wrote:
> Hi!
> 
> The following testcase reduced from newlib ICEs on powerpc-linux,
> with -O2 -m32 -mpowerpc64 since r12-6433 PR102239 optimization was
> added and on the original testcase since some ranger improvements in
> GCC 13 made it no longer latent on newlib.
> The problem is that the *branch_anddi3_dot define_insn_and_split
> relies on the *rotldi3_mask_dot define_insn_and_split being recognized
> during splitting.  The rs6000_is_valid_rotate_dot_mask function checks whether
> the mask is a CONST_INT which is a valid mask, but *rotl<mode>3_mask_dot in
> addition to checking that it is a valid mask also has
>   (<MODE>mode == Pmode || UINTVAL (operands[3]) <= 0x7fffffff)
> test in the condition.  For TARGET_64BIT that doesn't add any further
> requirements, but for !TARGET_64BIT && TARGET_POWERPC64 if the AND
> second operand is larger than INT_MAX it will not be recognized.
> 

For the associated test case, it looks it's valid to make use of rldicr.
(rolt with dot), so an alternative seems to relax the condition of
*rotldi3_mask_dot.  Considering this is also targeted for 13.1, I think
this proposed fix is much more conservative, thus this looks good to me!
I also expect Segher/David can give a final say. :)

Two nits are inline as below:

> The rs6000_is_valid_rotate_dot_mask function is used solely in one spot,
> condition of *branch_anddi3_dot, so the following patch adjusts it
> to check for that as well.
> 
> Bootstrapped/regtested on powerpc64-linux (-m32/-m64) and powerpc64le-linux,
> ok for trunk/13.1/12.3?
> 
> 2023-04-24  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR target/109566
> 	* config/rs6000/rs6000.cc (rs6000_is_valid_rotate_dot_mask): For
> 	!TARGET_64BIT, don't return true if UINTVAL (mask) << (63 - nb)
> 	is larger than signed int maximum.
> 
> 	* gcc.target/powerpc/pr109566.c: New test.
> 
> --- gcc/config/rs6000/rs6000.cc.jj	2023-04-04 10:33:47.433201866 +0200
> +++ gcc/config/rs6000/rs6000.cc	2023-04-24 12:31:07.237031550 +0200
> @@ -11409,7 +11409,16 @@ bool
>  rs6000_is_valid_rotate_dot_mask (rtx mask, machine_mode mode)
>  {
>    int nb, ne;
> -  return rs6000_is_valid_mask (mask, &nb, &ne, mode) && nb >= ne && ne > 0;
> +  if (rs6000_is_valid_mask (mask, &nb, &ne, mode) && nb >= ne && ne > 0)
> +    {
> +      if (TARGET_64BIT)
> +	return true;
> +      /* *rotldi3_mask_dot requires for -m32 -mpowerpc64 that the mask is
> +	 <= 0x7ffffff.  */

typo, a "f" is missing in "0x7ffffff".

> +      return (UINTVAL (mask) << (63 - nb)) <= 0x7fffffff;
> +    }
> +  else
> +    return false;
>  }
> 
>  /* Return whether MASK (a CONST_INT) is a valid mask for any rlwinm, rldicl,
> --- gcc/testsuite/gcc.target/powerpc/pr109566.c.jj	2023-04-24 12:54:48.293266468 +0200
> +++ gcc/testsuite/gcc.target/powerpc/pr109566.c	2023-04-24 12:34:34.306006418 +0200
> @@ -0,0 +1,15 @@
> +/* PR target/109566 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -mpowerpc64" } */

/* { dg-skip-if "" { powerpc*-*-aix* } { "*" } { "" } } */

Like 749140af5d072a, we have to exclude this to be tested on aix, otherwise the
-maix32 and -mpowerpc64 can cause an error message on aix like:

error: '-maix64' required: 64-bit computation with 32-bit addressing not yet supported

BR,
Kewen