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 --git a/gcc/testsuite/gfortran.dg/pr101026.f b/gcc/testsuite/gfortran.dg/pr101026.f
new file mode 100644 (file)
index 0000000..9576d88
--- /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 6237a61..897bd6f 100644 (file)
--- 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.  */