Ping
On 10/09/23 10:58 pm, Surya Kumari Jangala 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.
>
> Another issue is that existing code treats non-permuting loads/stores
> as special swappables. Non-permuting loads/stores (that have not yet
> been split into a permuting load/store and a swap) are handled by
> converting them into a permuting load/store (which effectively removes
> the swap). As a result, if special swappables are handled only in webs
> containing permuting loads/stores, then non-optimal code is generated
> for non-permuting loads/stores.
>
> Hence, in this patch, all webs containing either permuting loads/
> stores or non-permuting loads/stores are marked as requiring special
> handling of swappables. Swaps associated with permuting loads/stores
> are marked for removal, and non-permuting loads/stores are converted to
> permuting loads/stores. Then the special swappables in the webs are
> fixed up.
>
> Another issue with always handling swappable instructions is that it is
> incorrect to do so 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.
>
> 2023-09-10 Surya Kumari Jangala <jskum...@linux.ibm.com>
>
> gcc/
> PR rtl-optimization/PR106770
> * config/rs6000/rs6000-p8swap.cc (non_permuting_mem_insn): New
> function.
> (handle_non_permuting_mem_insn): New function.
> (rs6000_analyze_swaps): Handle swappable instructions only in
> certain webs.
> (web_requires_special_handling): New instance variable.
> (handle_special_swappables): Remove handling of non-permuting
> load/store instructions.
>
> gcc/testsuite/
> PR rtl-optimization/PR106770
> * gcc.target/powerpc/pr106770.c: New test.
> ---
>
> diff --git a/gcc/config/rs6000/rs6000-p8swap.cc
> b/gcc/config/rs6000/rs6000-p8swap.cc
> index 0388b9bd736..3a695aa1318 100644
> --- a/gcc/config/rs6000/rs6000-p8swap.cc
> +++ b/gcc/config/rs6000/rs6000-p8swap.cc
> @@ -179,6 +179,13 @@ 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 swappable insns in the web represented by this entry
> + have to be fixed. Swappable insns have to be fixed in :
> + - webs containing permuting loads/stores and the swap insns
> + in such webs have been marked for removal
> + - webs where non-permuting loads/stores have been converted
> + to permuting loads/stores */
> + unsigned int web_requires_special_handling : 1;
> /* Set if this insn should be deleted. */
> unsigned int will_delete : 1;
> };
> @@ -1468,14 +1475,6 @@ handle_special_swappables (swap_web_entry *insn_entry,
> unsigned i)
> if (dump_file)
> fprintf (dump_file, "Adjusting subreg in insn %d\n", i);
> break;
> - case SH_NOSWAP_LD:
> - /* Convert a non-permuting load to a permuting one. */
> - permute_load (insn);
> - break;
> - case SH_NOSWAP_ST:
> - /* Convert a non-permuting store to a permuting one. */
> - permute_store (insn);
> - break;
> case SH_EXTRACT:
> /* Change the lane on an extract operation. */
> adjust_extract (insn);
> @@ -2401,6 +2400,25 @@ recombine_lvx_stvx_patterns (function *fun)
> free (to_delete);
> }
>
> +/* Return true if insn is a non-permuting load/store. */
> +static bool
> +non_permuting_mem_insn (swap_web_entry *insn_entry, unsigned int i)
> +{
> + return (insn_entry[i].special_handling == SH_NOSWAP_LD ||
> + insn_entry[i].special_handling == SH_NOSWAP_ST);
> +}
> +
> +/* Convert a non-permuting load/store insn to a permuting one. */
> +static void
> +handle_non_permuting_mem_insn (swap_web_entry *insn_entry, unsigned int i)
> +{
> + rtx_insn *insn = insn_entry[i].insn;
> + if (insn_entry[i].special_handling == SH_NOSWAP_LD)
> + permute_load (insn);
> + else if (insn_entry[i].special_handling == SH_NOSWAP_ST)
> + permute_store (insn);
> +}
> +
> /* Main entry point for this pass. */
> unsigned int
> rs6000_analyze_swaps (function *fun)
> @@ -2624,25 +2642,56 @@ rs6000_analyze_swaps (function *fun)
> dump_swap_insn_table (insn_entry);
> }
>
> - /* 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. */
> + /* There are two kinds of optimizations that can be performed on an
> + optimizable web:
> + 1. Remove the register swaps associated with permuting load/store
> + in an optimizable web
> + 2. Convert the vanilla loads/stores (that have not yet been split
> + into a permuting load/store and a swap) into a permuting
> + load/store (which effectively removes the swap)
> + In both the cases, swappable instructions in the webs need
> + special handling to fix them up. */
> for (i = 0; i < e; ++i)
> + /* For each permuting load/store in an optimizable web, find
> + the associated register swaps and mark them for removal.
> + Due to various optimizations we may mark the same swap more
> + than once. */
> 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)
> - mark_swaps_for_removal (insn_entry, i);
> + {
> + mark_swaps_for_removal (insn_entry, i);
> + root_entry->web_requires_special_handling = true;
> + }
> }
> - else if (insn_entry[i].is_swappable && insn_entry[i].special_handling)
> + /* Convert the non-permuting loads/stores into a permuting
> + load/store. */
> + else if (insn_entry[i].is_swappable
> + && non_permuting_mem_insn (insn_entry, i))
> {
> swap_web_entry* root_entry
> = (swap_web_entry*)((&insn_entry[i])->unionfind_root ());
> if (!root_entry->web_not_optimizable)
> + {
> + handle_non_permuting_mem_insn (insn_entry, i);
> + root_entry->web_requires_special_handling = 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 marked as requiring
> + special handling. */
> + for (i = 0; i < e; ++i)
> + if (insn_entry[i].is_swappable && insn_entry[i].special_handling &&
> + !non_permuting_mem_insn (insn_entry, i))
> + {
> + swap_web_entry* root_entry
> + = (swap_web_entry*)((&insn_entry[i])->unionfind_root ());
> + if (root_entry->web_requires_special_handling)
> 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..11efe39abc5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr106770.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target powerpc_p8vector_ok } */
> +/* { dg-options "-mdejagnu-cpu=power8 -O2 " } */
> +/* The 2 xxpermdi instructions are generated by the two
> + calls to vec_promote() */
> +/* { 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);
> +}
>
