Don't vectorise single-iteration epilogues

With a later patch I saw a case in which we peeled a single iteration
for gaps but didn't need to peel further iterations to make up a full
vector.  We then tried to vectorise the single-iteration epilogue.

2019-11-06  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-loop.c (vect_analyze_loop): Only try to vectorize
	the epilogue if there are peeled iterations for it to handle.

From-SVN: r277886

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1ff3d4b..daf1194 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2019-11-06  Richard Sandiford  <richard.sandiford@arm.com>
+
+       * tree-vect-loop.c (vect_analyze_loop): Only try to vectorize
+       the epilogue if there are peeled iterations for it to handle.
+
 2019-11-06  Claudiu Zissulescu  <claziss@synopsys.com>
 
        * config/arc/arc.c (arc_split_ior): Add asserts.

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index d982e1a..788cc87 100644 (file)
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -2459,6 +2459,7 @@ vect_analyze_loop (class loop *loop, vec_info_shared *shared)
          vect_epilogues = (!loop->simdlen
                            && loop->inner == NULL
                            && PARAM_VALUE (PARAM_VECT_EPILOGUES_NOMASK)
+                           && LOOP_VINFO_PEELING_FOR_NITER (first_loop_vinfo)
                            /* For now only allow one epilogue loop.  */
                            && first_loop_vinfo->epilogue_vinfos.is_empty ());