tree-optimization/114027 - conditional reduction chain

When we classify a conditional reduction chain as CONST_COND_REDUCTION
we fail to verify all involved conditionals have the same constant.
That's a quite unlikely situation so the following simply disables
such classification when there's more than one reduction statement.

	PR tree-optimization/114027
	* tree-vect-loop.cc (vecctorizable_reduction): Use optimized
	condition reduction classification only for single-element
	chains.

	* gcc.dg/vect/pr114027.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/vect/pr114027.c b/gcc/testsuite/gcc.dg/vect/pr114027.c
new file mode 100644 (file)
index 0000000..ead9cdd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr114027.c
@@ -0,0 +1,26 @@
+#include "tree-vect.h"
+
+int __attribute__((noipa))
+foo (int *f, int n)
+{
+  int res = 0;
+  for (int i = 0; i < n; ++i)
+    {
+      if (f[2*i])
+        res = 2;
+      if (f[2*i+1])
+        res = -2;
+    }
+  return res;
+}
+
+int f[] = { 1, 1, 1, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 0 };
+
+int
+main ()
+{
+  if (foo (f, 16) != 2)
+    __builtin_abort ();
+  return 0;
+}

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 5a5865c42fc6298ea7e4d486b3bb3e2dc825a118..35f1f8c7d4245135ace7ffff40ff9be548919587 100644 (file)
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -7759,17 +7759,18 @@ vectorizable_reduction (loop_vec_info loop_vinfo,
                  < GET_MODE_SIZE (SCALAR_TYPE_MODE (TREE_TYPE (vectype_op[i]))))))
        vectype_in = vectype_op[i];
 
-      if (op.code == COND_EXPR)
+      /* Record how the non-reduction-def value of COND_EXPR is defined.
+        ???  For a chain of multiple CONDs we'd have to match them up all.  */
+      if (op.code == COND_EXPR && reduc_chain_length == 1)
        {
-         /* Record how the non-reduction-def value of COND_EXPR is defined.  */
          if (dt == vect_constant_def)
            {
              cond_reduc_dt = dt;
              cond_reduc_val = op.ops[i];
            }
-         if (dt == vect_induction_def
-             && def_stmt_info
-             && is_nonwrapping_integer_induction (def_stmt_info, loop))
+         else if (dt == vect_induction_def
+                  && def_stmt_info
+                  && is_nonwrapping_integer_induction (def_stmt_info, loop))
            {
              cond_reduc_dt = dt;
              cond_stmt_vinfo = def_stmt_info;