middle-end: fix epilog reductions when vector iters peeled [PR113364]

This fixes a bug where vect_create_epilog_for_reduction does not handle the
case where all exits are early exits.  In this case we should do like induction
handling code does and not have a main exit.

This shows that some new miscompiles are happening (stage3 is likely miscompiled)
but that's unrelated to this patch and I'll look at it next.

gcc/ChangeLog:

	PR tree-optimization/113364
	* tree-vect-loop.cc (vect_create_epilog_for_reduction): If all exits all
	early exits then we must reduce from the first offset for all of them.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113364
	* gcc.dg/vect/vect-early-break_107-pr113364.c: New test.

diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_107-pr113364.c b/gcc/testsuite/gcc.dg/vect/vect-early-break_107-pr113364.c
new file mode 100644 (file)
index 0000000..f489265
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_107-pr113364.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-add-options vect_early_break } */
+/* { dg-require-effective-target vect_early_break } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-additional-options "-w" } */
+
+typedef const unsigned char *It;
+It DecodeSLEB128(It begin, It end, int *v) {
+  int value = 0;
+  unsigned shift = 0;
+  unsigned char byte;
+  do
+  {
+    if (begin == end)
+      return begin;
+    byte = *(begin++);
+    int slice = byte & 0x7f;
+    value |= slice << shift;
+  } while (byte >= 128);
+  *v = value;
+  return begin;
+}

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index fe631252dc2258e8ea42179b4ba068a480be9e38..4da1421c8f09746ef4b293573e4f861b642349e1 100644 (file)
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -5982,7 +5982,8 @@ vect_create_epilog_for_reduction (loop_vec_info loop_vinfo,
      loop-closed PHI of the inner loop which we remember as
      def for the reduction PHI generation.  */
   bool double_reduc = false;
-  bool main_exit_p = LOOP_VINFO_IV_EXIT (loop_vinfo) == loop_exit;
+  bool main_exit_p = LOOP_VINFO_IV_EXIT (loop_vinfo) == loop_exit
+                    && !LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo);
   stmt_vec_info rdef_info = stmt_info;
   if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_double_reduction_def)
     {