Fix PR tree-optimization/47139
diff mbox

Message ID OFBC2926A1.DDFE58AD-ONC2257810.0026EF35-C2257810.0029A8ED@il.ibm.com
State New
Headers show

Commit Message

Ira Rosen Jan. 6, 2011, 7:35 a.m. 
Hi,

This patch adds a check that only the last reduction value is used outside
the vectorized loop.

Bootstrapped with vectorization enabled and tested on powerpc64-suse-linux.
Committed.

Ira

ChangeLog:

	PR tree-optimization/47139
	* tree-vect-loop.c (vect_is_simple_reduction_1): Check that
	only the last reduction value is used outside the loop. Update
	documentation.

testsuite/ChangeLog:

	PR tree-optimization/47139
	* gcc.dg/vect/pr47139.c: New test.

Patch
diff mbox 

Index: testsuite/gcc.dg/vect/pr47139.c
===================================================================
--- testsuite/gcc.dg/vect/pr47139.c     (revision 0)
+++ testsuite/gcc.dg/vect/pr47139.c     (revision 0)
@@ -0,0 +1,18 @@ 
+/* { dg-do compile } */
+
+int d;
+
+void
+foo ()
+{
+  int a = 0;
+  unsigned char b;
+  for (b = 1; b; b++)
+    {
+      d = a;
+      a |= b;
+    }
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */
+
Index: tree-vect-loop.c
===================================================================
--- tree-vect-loop.c    (revision 168534)
+++ tree-vect-loop.c    (working copy)
@@ -1649,9 +1649,10 @@  report_vect_op (gimple stmt, const char *msg)
    1. operation is commutative and associative and it is safe to
       change the order of the computation (if CHECK_REDUCTION is true)
    2. no uses for a2 in the loop (a2 is used out of the loop)
-   3. no uses of a1 in the loop besides the reduction operation.
+   3. no uses of a1 in the loop besides the reduction operation
+   4. no uses of a1 outside the loop.

-   Condition 1 is tested here.
+   Conditions 1,4 are tested here.
    Conditions 2,3 are tested in vect_mark_stmts_to_be_vectorized.

    (2) Detect a cross-iteration def-use cycle in nested loops, i.e.,
@@ -1702,8 +1703,16 @@  vect_is_simple_reduction_1 (loop_vec_info loop_inf
       gimple use_stmt = USE_STMT (use_p);
       if (is_gimple_debug (use_stmt))
        continue;
-      if (flow_bb_inside_loop_p (loop, gimple_bb (use_stmt))
-         && vinfo_for_stmt (use_stmt)
+
+      if (!flow_bb_inside_loop_p (loop, gimple_bb (use_stmt)))
+        {
+          if (vect_print_dump_info (REPORT_DETAILS))
+            fprintf (vect_dump, "intermediate value used outside loop.");
+
+          return NULL;
+        }
+
+      if (vinfo_for_stmt (use_stmt)
          && !is_pattern_stmt_p (vinfo_for_stmt (use_stmt)))
         nloop_uses++;
       if (nloop_uses > 1)