tree-optimization/102046 - fix SLP build from scalars with patterns

When we swap operands for SLP builds we lose track where exactly
pattern defs are - but we fail to update the any_pattern member
of the operands info.  Do so conservatively.

2021-08-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102046
	* tree-vect-slp.c (vect_build_slp_tree_2): Conservatively
	update ->any_pattern when swapping operands.

	* gcc.dg/vect/pr102046.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/vect/pr102046.c b/gcc/testsuite/gcc.dg/vect/pr102046.c
new file mode 100644 (file)
index 0000000..ae48b49
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr102046.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O3 -fvect-cost-model=dynamic" } */
+/* { dg-additional-options "-march=btver2" { target x86_64-*-* i?86-*-* } } */
+
+struct S
+{
+  unsigned a, b;
+};
+
+struct S g;
+
+void
+foo (struct S *o)
+{
+  struct S s = g;
+  s.b *= 3;
+  s.a -= s.a / 2;
+  *o = s;
+}

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index edc11c6..4d688c7 100644 (file)
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2311,6 +2311,10 @@ out:
              }
          if (dump_enabled_p ())
            dump_printf (MSG_NOTE, "\n");
+         /* After swapping some operands we lost track whether an
+            operand has any pattern defs so be conservative here.  */
+         if (oprnds_info[0]->any_pattern || oprnds_info[1]->any_pattern)
+           oprnds_info[0]->any_pattern = oprnds_info[1]->any_pattern = true;
          /* And try again with scratch 'matches' ... */
          bool *tem = XALLOCAVEC (bool, group_size);
          if ((child = vect_build_slp_tree (vinfo, oprnd_info->def_stmts,