[patch] Fix PR tree-optimization/50412

[Ira Rosen]

Hi,

Strided accesses of single element or with gaps may require creation
of epilogue loop. At the moment we don't support peeling for outer
loops, therefore, we should not allow such strided accesses in outer
loops.

Bootstrapped and tested on powerpc64-suse-linux.
Committed to trunk.

Now testing for 4.6.
OK for 4.6 when the testing completes?

Thanks,
Ira

ChangeLog:

        PR tree-optimization/50412
        * tree-vect-data-refs.c (vect_analyze_group_access): Fail for
        acceses that require epilogue loop if vectorizing outer loop.

testsuite/ChangeLog:

        PR tree-optimization/50412
        * gfortran.dg/vect/pr50412.f90: New.



Index: tree-vect-data-refs.c
===================================================================
--- tree-vect-data-refs.c       (revision 178939)
+++ tree-vect-data-refs.c       (working copy)
@@ -2060,7 +2060,11 @@ vect_analyze_group_access (struct data_reference *
   HOST_WIDE_INT dr_step = TREE_INT_CST_LOW (step);
   HOST_WIDE_INT stride, last_accessed_element = 1;
   bool slp_impossible = false;
+  struct loop *loop = NULL;

+  if (loop_vinfo)
+    loop = LOOP_VINFO_LOOP (loop_vinfo);
+
   /* For interleaving, STRIDE is STEP counted in elements, i.e., the
size of the
      interleaving group (including gaps).  */
   stride = dr_step / type_size;
@@ -2090,11 +2094,18 @@ vect_analyze_group_access (struct data_reference *

          if (loop_vinfo)
            {
-             LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
-
              if (vect_print_dump_info (REPORT_DETAILS))
                fprintf (vect_dump, "Data access with gaps requires scalar "
                                    "epilogue loop");
+              if (loop->inner)
+                {
+                  if (vect_print_dump_info (REPORT_DETAILS))
+                    fprintf (vect_dump, "Peeling for outer loop is not"
+                                        " supported");
+                  return false;
+                }
+
+              LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
            }

          return true;
@@ -2277,10 +2288,17 @@ vect_analyze_group_access (struct data_reference *
       /* There is a gap in the end of the group.  */
       if (stride - last_accessed_element > 0 && loop_vinfo)
        {
-         LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
          if (vect_print_dump_info (REPORT_DETAILS))
            fprintf (vect_dump, "Data access with gaps requires scalar "
                                "epilogue loop");
+          if (loop->inner)
+            {
+              if (vect_print_dump_info (REPORT_DETAILS))
+                fprintf (vect_dump, "Peeling for outer loop is not supported");
+              return false;
+            }
+
+          LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
        }
     }
Index: testsuite/gfortran.dg/vect/pr50412.f90
===================================================================
--- testsuite/gfortran.dg/vect/pr50412.f90      (revision 0)
+++ testsuite/gfortran.dg/vect/pr50412.f90      (revision 0)
@@ -0,0 +1,12 @@
+! { dg-do compile }
+
+      DOUBLE PRECISION AK,AI,AAE
+      COMMON/com/AK(36),AI(4,4),AAE(8,4),ii,jj
+      DO 20 II=1,4
+        DO 21 JJ=1,4
+          AK(n)=AK(n)-AAE(I,II)*AI(II,JJ)
+   21   CONTINUE
+   20 CONTINUE
+      END
+
+! { dg-final { cleanup-tree-dump "vect" } }