[gcc r12-1387] tree-optimization/101026 - fix SLP re-association

[gcc r12-1387] tree-optimization/101026 - fix SLP re-association

[Richard Biener]

https://gcc.gnu.org/g:fbd8a8041292f2ec2c22be43c8d3e74b37b2bc88

commit r12-1387-gfbd8a8041292f2ec2c22be43c8d3e74b37b2bc88
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Jun 11 13:33:17 2021 +0200

    tree-optimization/101026 - fix SLP re-association
    
    Since we cannot yet encode the operation in the SLP node itself
    but need a representative stmt require an existing one for now
    to avoid the need to build a fake GIMPLE stmt.
    
    2021-06-11  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/101026
            * tree-vect-slp.c (vect_build_slp_tree_2): Make sure we
            have a representative for the associated chain nodes.
    
            * gfortran.dg/pr101026.f: New testcase.

Diff:
---
 gcc/testsuite/gfortran.dg/pr101026.f | 11 +++++++++++
 gcc/tree-vect-slp.c                  |  4 +++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gfortran.dg/pr101026.f b/gcc/testsuite/gfortran.dg/pr101026.f
new file mode 100644
index 00000000000..9576d8802ca
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr101026.f
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! { dg-options "-Ofast -frounding-math" }
+      SUBROUTINE PASSB4 (CC,CH)
+      DIMENSION CC(IDO,4,L1), CH(IDO,L1,*)
+         DO 103 I=2,IDO,2
+            TI4 = CC0-CC(I,4,K)
+            CI4 = TI1-TI4
+            CH(I-1,K,4) = CI4
+            CH(I,K,4) = CI4
+  103    CONTINUE
+      END
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 6237a61ffd4..897bd6f37b9 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -1860,7 +1860,9 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
 	  chains.quick_push (chain.copy ());
 	  chain.truncate (0);
 	}
-      if (chains.length () == group_size)
+      if (chains.length () == group_size
+	  /* We cannot yet use SLP_TREE_CODE to communicate the operation.  */
+	  && op_stmt_info)
 	{
 	  /* Now we have a set of chains with the same length.  */
 	  /* 1. pre-sort according to def_type and operation.  */