re PR tree-optimization/79943 (Loop splitting breaks with loops of pointer type)

2017-03-08  Andrew Haley  <aph@redhat.com>

	PR tree-optimization/79943
	* tree-ssa-loop-split.c (compute_new_first_bound): When
	calculating the new upper bound, (END-BEG) should be added, not
	subtracted.

From-SVN: r245974

gcc/ChangeLog

+2017-03-08  Andrew Haley  <aph@redhat.com>
+
+	PR tree-optimization/79943
+	* tree-ssa-loop-split.c (compute_new_first_bound): When
+	calculating the new upper bound, (END-BEG) should be added, not
+	subtracted.
+
 2017-03-08  Jakub Jelinek  <jakub@redhat.com>
 
 	* config/avr/avr.md (setmemhi): Make sure match_dup

gcc/testsuite/ChangeLog

+2017-03-08  Andrew Haley  <aph@redhat.com>
+
+	PR tree-optimization/79943
+	* gcc.dg/tree-ssa/pr79943.c: New test.
+
 2017-03-08  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/79920

gcc/testsuite/gcc.dg/tree-ssa/pr79943.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fsplit-loops -fdump-tree-lsplit-details" } */
+/* { dg-require-effective-target int32plus } */
+
+#ifdef __cplusplus
+extern "C" void abort (void);
+#else
+extern void abort (void);
+#endif
+
+typedef struct {
+  int n;
+} region_t;
+
+void set (region_t *region) __attribute__((noinline));
+void doit (region_t *beg, region_t *end, region_t *limit)
+  __attribute__((noinline));
+
+region_t regions[10];
+
+void
+set (region_t *region) {
+  region->n = 1;
+}
+
+void
+doit (region_t *beg, region_t *end, region_t *limit) {
+  for (region_t *cur = beg; cur < end; cur++) {
+    if (cur < limit) {
+      set(cur);
+    }
+  }
+}
+
+int
+main (void) {
+  doit(&regions[0], &regions[2], &regions[10]);
+  if (regions[1].n != 1)
+    abort();
+}

gcc/tree-ssa-loop-split.c

@@ -436,7 +436,6 @@ compute_new_first_bound (gimple_seq *stmts, struct tree_niter_desc *niter,
   if (POINTER_TYPE_P (TREE_TYPE (guard_init)))
     {
       enddiff = gimple_convert (stmts, sizetype, enddiff);
-      enddiff = gimple_build (stmts, NEGATE_EXPR, sizetype, enddiff);
       newbound = gimple_build (stmts, POINTER_PLUS_EXPR,
 			       TREE_TYPE (guard_init),
 			       guard_init, enddiff);