[gcc r13-1732] Fix builtin vs non-builtin partition merge in loop distribution

[gcc r13-1732] Fix builtin vs non-builtin partition merge in loop distribution

[Richard Biener]

https://gcc.gnu.org/g:87f46a16ec05beb51439f55a4d3c36d64b95b00f

commit r13-1732-g87f46a16ec05beb51439f55a4d3c36d64b95b00f
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Jul 18 13:09:57 2022 +0200

    Fix builtin vs non-builtin partition merge in loop distribution
    
    When r7-6373-g40b6bff965d004 fixed a costing issue it failed to
    make the logic symmetric which means that we now fuse
    normal vs. builtin when the cost model says so but we don't fuse
    builtin vs. normal.  The following fixes that, also allowing
    the cost model to decide to fuse two builtin partitions as otherwise
    an intermediate non-builtin can result in a partial merge as well.
    
            * tree-loop-distribution.cc (loop_distribution::distribute_loop):
            When computing cost-based merging do not disregard builtin
            classified partitions in some cases.
    
            * gcc.dg/tree-ssa/ldist-24.c: XFAIL.
            * gcc.dg/tree-ssa/ldist-36.c: Adjust expected outcome.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/ldist-24.c | 5 +++--
 gcc/testsuite/gcc.dg/tree-ssa/ldist-36.c | 3 ++-
 gcc/tree-loop-distribution.cc            | 5 +----
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ldist-24.c b/gcc/testsuite/gcc.dg/tree-ssa/ldist-24.c
index 75f7b8f0c88..2403a24293b 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ldist-24.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ldist-24.c
@@ -20,5 +20,6 @@ void foo ()
       }
 }
 
-/* { dg-final { scan-tree-dump "generated memcpy" "ldist" } } */
-/* { dg-final { scan-tree-dump "generated memset zero" "ldist" } } */
+/* The cost modeling does not consider WAR as beneficial to split.  */
+/* { dg-final { scan-tree-dump "generated memcpy" "ldist" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump "generated memset zero" "ldist" { xfail *-*-* } } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ldist-36.c b/gcc/testsuite/gcc.dg/tree-ssa/ldist-36.c
index 07393f0a665..6d560060e09 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ldist-36.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ldist-36.c
@@ -25,4 +25,5 @@ foo (struct st * restrict p)
     }
 }
 
-/* { dg-final { scan-tree-dump-times "Loop nest . distributed: split to 0 loops and 3 library" 1 "ldist" } } */
+/* The cost modeling doesn't consider splitting a WAR re-use profitable.  */
+/* { dg-final { scan-tree-dump-times "Loop nest . distributed: split to 1 loops and 1 library" 1 "ldist" } } */
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index 0714bc41a43..0ee441c077d 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -3090,10 +3090,7 @@ loop_distribution::distribute_loop (class loop *loop,
   for (i = 0; partitions.iterate (i, &into); ++i)
     {
       bool changed = false;
-      if (partition_builtin_p (into) || into->kind == PKIND_PARTIAL_MEMSET)
-	continue;
-      for (int j = i + 1;
-	   partitions.iterate (j, &partition); ++j)
+      for (int j = i + 1; partitions.iterate (j, &partition); ++j)
 	{
 	  if (share_memory_accesses (rdg, into, partition))
 	    {