[gcc r12-6203] tree-optimization/103864 - SLP reduction of reductions with conversions

[Richard Biener]

https://gcc.gnu.org/g:1a15451da14410bf2bd6ec8f5baba1014638c67a

commit r12-6203-g1a15451da14410bf2bd6ec8f5baba1014638c67a
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Jan 4 10:12:47 2022 +0100

    tree-optimization/103864 - SLP reduction of reductions with conversions
    
    This generalizes the fix for PR103544 to also cover reductions that
    are not reduction chains and does not consider reductions wrapped in
    sign conversions for SLP reduction handling.
    
    2022-01-04  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/103864
            PR tree-optimization/103544
            * tree-vect-slp.c (vect_analyze_slp_instance): Exclude
            reductions wrapped in conversions from SLP handling.
            (vect_analyze_slp): Revert PR103544 change.
    
            * gcc.dg/vect/pr103864.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr103864.c | 16 ++++++++++++++++
 gcc/tree-vect-slp.c                  | 18 +++++++++---------
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/vect/pr103864.c b/gcc/testsuite/gcc.dg/vect/pr103864.c
new file mode 100644
index 00000000000..464d5731a42
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr103864.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O3 -fno-tree-reassoc" } */
+
+void
+crash_me (short int *crash_me_result, int i, char crash_me_ptr_0)
+{
+  while (i < 1)
+    {
+      int j;
+
+      for (j = 0; j < 2; ++j)
+        crash_me_result[j] += crash_me_ptr_0 + 1;
+
+      i += 3;
+    }
+}
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 3566752c657..c3a1681d7c6 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -3325,8 +3325,13 @@ vect_analyze_slp_instance (vec_info *vinfo,
 	= as_a <loop_vec_info> (vinfo)->reductions;
       scalar_stmts.create (reductions.length ());
       for (i = 0; reductions.iterate (i, &next_info); i++)
-	if (STMT_VINFO_RELEVANT_P (next_info)
-	    || STMT_VINFO_LIVE_P (next_info))
+	if ((STMT_VINFO_RELEVANT_P (next_info)
+	     || STMT_VINFO_LIVE_P (next_info))
+	    /* ???  Make sure we didn't skip a conversion around a reduction
+	       path.  In that case we'd have to reverse engineer that conversion
+	       stmt following the chain using reduc_idx and from the PHI
+	       using reduc_def.  */
+	    && STMT_VINFO_DEF_TYPE (next_info) == vect_reduction_def)
 	  scalar_stmts.quick_push (next_info);
       /* If less than two were relevant/live there's nothing to SLP.  */
       if (scalar_stmts.length () < 2)
@@ -3419,13 +3424,8 @@ vect_analyze_slp (vec_info *vinfo, unsigned max_tree_size)
 		vinfo = next;
 	      }
 	    STMT_VINFO_DEF_TYPE (first_element) = vect_internal_def;
-	    /* It can be still vectorized as part of an SLP reduction.
-	       ???  But only if we didn't skip a conversion around the group.
-	       In that case we'd have to reverse engineer that conversion
-	       stmt following the chain using reduc_idx and from the PHI
-	       using reduc_def.  */
-	    if (STMT_VINFO_DEF_TYPE (last) == vect_reduction_def)
-	      loop_vinfo->reductions.safe_push (last);
+	    /* It can be still vectorized as part of an SLP reduction.  */
+	    loop_vinfo->reductions.safe_push (last);
 	  }
 
       /* Find SLP sequences starting from groups of reductions.  */