[PING] [PATCH] swap: Fix incorrect lane extraction by vec_extract() [PR106770]

[Surya Kumari Jangala <jskumari@linux.vnet.ibm.com>]

Ping

On 04/01/23 1:58 pm, Surya Kumari Jangala via Gcc-patches wrote:
> swap: Fix incorrect lane extraction by vec_extract() [PR106770]
> 
> In the routine rs6000_analyze_swaps(), special handling of swappable
> instructions is done even if the webs that contain the swappable
> instructions are not optimized, i.e., the webs do not contain any
> permuting load/store instructions along with the associated register
> swap instructions. Doing special handling in such webs will result in
> the extracted lane being adjusted unnecessarily for vec_extract.
> 
> Modifying swappable instructions is also incorrect in webs where
> loads/stores on quad word aligned addresses are changed to lvx/stvx.
> Similarly, in webs where swap(load(vector constant)) instructions are
> replaced with load(swapped vector constant), the swappable
> instructions should not be modified.
> 
> 2023-01-04  Surya Kumari Jangala  <jskumari@linux.ibm.com>
> 
> gcc/
> 	PR rtl-optimization/106770
> 	* rs6000-p8swap.cc (rs6000_analyze_swaps): .
> 
> gcc/testsuite/
> 	PR rtl-optimization/106770
> 	* gcc.target/powerpc/pr106770.c: New test.
> ---
> 
> diff --git a/gcc/config/rs6000/rs6000-p8swap.cc b/gcc/config/rs6000/rs6000-p8swap.cc
> index 19fbbfb67dc..7ed39251df9 100644
> --- a/gcc/config/rs6000/rs6000-p8swap.cc
> +++ b/gcc/config/rs6000/rs6000-p8swap.cc
> @@ -179,6 +179,9 @@ class swap_web_entry : public web_entry_base
>    unsigned int special_handling : 4;
>    /* Set if the web represented by this entry cannot be optimized.  */
>    unsigned int web_not_optimizable : 1;
> +  /* Set if the web represented by this entry has been optimized, ie,
> +     register swaps of permuting loads/stores have been removed.  */
> +  unsigned int web_is_optimized : 1;
>    /* Set if this insn should be deleted.  */
>    unsigned int will_delete : 1;
>  };
> @@ -2627,22 +2630,43 @@ rs6000_analyze_swaps (function *fun)
>    /* For each load and store in an optimizable web (which implies
>       the loads and stores are permuting), find the associated
>       register swaps and mark them for removal.  Due to various
> -     optimizations we may mark the same swap more than once.  Also
> -     perform special handling for swappable insns that require it.  */
> +     optimizations we may mark the same swap more than once. Fix up
> +     the non-permuting loads and stores by converting them into
> +     permuting ones.  */
>    for (i = 0; i < e; ++i)
>      if ((insn_entry[i].is_load || insn_entry[i].is_store)
>  	&& insn_entry[i].is_swap)
>        {
>  	swap_web_entry* root_entry
>  	  = (swap_web_entry*)((&insn_entry[i])->unionfind_root ());
> -	if (!root_entry->web_not_optimizable)
> +	if (!root_entry->web_not_optimizable) {
>  	  mark_swaps_for_removal (insn_entry, i);
> +          root_entry->web_is_optimized = true;
> +        }
>        }
> -    else if (insn_entry[i].is_swappable && insn_entry[i].special_handling)
> +    else if (insn_entry[i].is_swappable
> +             && (insn_entry[i].special_handling == SH_NOSWAP_LD ||
> +                 insn_entry[i].special_handling == SH_NOSWAP_ST))
> +      {
> +        swap_web_entry* root_entry
> +          = (swap_web_entry*)((&insn_entry[i])->unionfind_root ());
> +        if (!root_entry->web_not_optimizable) {
> +          handle_special_swappables (insn_entry, i);
> +          root_entry->web_is_optimized = true;
> +        }
> +      }
> +
> +  /* Perform special handling for swappable insns that require it. 
> +     Note that special handling should be done only for those 
> +     swappable insns that are present in webs optimized above.  */
> +  for (i = 0; i < e; ++i)
> +    if (insn_entry[i].is_swappable && insn_entry[i].special_handling &&
> +        !(insn_entry[i].special_handling == SH_NOSWAP_LD || 
> +          insn_entry[i].special_handling == SH_NOSWAP_ST))
>        {
>  	swap_web_entry* root_entry
>  	  = (swap_web_entry*)((&insn_entry[i])->unionfind_root ());
> -	if (!root_entry->web_not_optimizable)
> +	if (root_entry->web_is_optimized)
>  	  handle_special_swappables (insn_entry, i);
>        }
>  
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106770.c b/gcc/testsuite/gcc.target/powerpc/pr106770.c
> new file mode 100644
> index 00000000000..84e9aead975
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr106770.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target powerpc_p8vector_ok } */
> +/* { dg-options "-mdejagnu-cpu=power8 -O3 " } */
> +/* { dg-final { scan-assembler-times "xxpermdi" 2 } } */
> +
> +/* Test case to resolve PR106770  */
> +
> +#include <altivec.h>
> +
> +int cmp2(double a, double b)
> +{
> +    vector double va = vec_promote(a, 1);
> +    vector double vb = vec_promote(b, 1);
> +    vector long long vlt = (vector long long)vec_cmplt(va, vb);
> +    vector long long vgt = (vector long long)vec_cmplt(vb, va);
> +    vector signed long long vr = vec_sub(vlt, vgt);
> +
> +    return vec_extract(vr, 1);
> +}
> +