[PATCH] Fixing PR60656

[Cong Hou]

This patch is fixing PR60656. Elements in a vector with
vect_used_by_reduction property cannot be reordered if the use chain
with this property does not have the same operation.

Bootstrapped and tested on a x86-64 machine.

OK for trunk?


thanks,
Cong


diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e1d8666..d7d5b82 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2014-03-28  Cong Hou  <co...@google.com>
+
+ PR tree-optimization/60656
+ * tree-vect-stmts.c (supportable_widening_operation):
+ Fix a bug that elements in a vector with vect_used_by_reduction
+ property are incorrectly reordered when the operation on it is not
+ consistant with the one in reduction operation.
+
 2014-03-10  Jakub Jelinek  <ja...@redhat.com>

  PR ipa/60457
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 41b6875..414a745 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-03-28  Cong Hou  <co...@google.com>
+
+ PR tree-optimization/60656
+ * gcc.dg/vect/pr60656.c: New test.
+
 2014-03-10  Jakub Jelinek  <ja...@redhat.com>

  PR ipa/60457
diff --git a/gcc/testsuite/gcc.dg/vect/pr60656.c
b/gcc/testsuite/gcc.dg/vect/pr60656.c
new file mode 100644
index 0000000..ebaab62
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr60656.c
@@ -0,0 +1,45 @@
+/* { dg-require-effective-target vect_int } */
+
+#include "tree-vect.h"
+
+__attribute__ ((noinline)) long
+foo ()
+{
+  int v[] = {5000, 5001, 5002, 5003};
+  long s = 0;
+  int i;
+
+  for(i = 0; i < 4; ++i)
+    {
+      long P = v[i];
+      s += P*P*P;
+    }
+  return s;
+}
+
+long
+bar ()
+{
+  int v[] = {5000, 5001, 5002, 5003};
+  long s = 0;
+  int i;
+
+  for(i = 0; i < 4; ++i)
+    {
+      long P = v[i];
+      s += P*P*P;
+      __asm__ volatile ("");
+    }
+  return s;
+}
+
+int main()
+{
+  if (foo () != bar ())
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
+
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 70fb411..7442d0c 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -7827,7 +7827,16 @@ supportable_widening_operation (enum tree_code
code, gimple stmt,
      stmt, vectype_out, vectype_in,
      code1, code2, multi_step_cvt,
      interm_types))
- return true;
+        {
+          tree lhs = gimple_assign_lhs (stmt);
+          use_operand_p dummy;
+          gimple use_stmt;
+          stmt_vec_info use_stmt_info = NULL;
+          if (single_imm_use (lhs, &dummy, &use_stmt)
+              && (use_stmt_info = vinfo_for_stmt (use_stmt))
+              && STMT_VINFO_DEF_TYPE (use_stmt_info) == vect_reduction_def)
+            return true;
+        }
       c1 = VEC_WIDEN_MULT_LO_EXPR;
       c2 = VEC_WIDEN_MULT_HI_EXPR;
       break;