re PR tree-optimization/90716 (gcc generates wrong debug information at -O2)

2019-06-03  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90716
	* tree-loop-distribution.c (destroy_loop): Process blocks in
	correct order.

	* gcc.dg/guality/pr90716.c: New testcase.

From-SVN: r271858

gcc/ChangeLog

+2019-06-03  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/90716
+	* tree-loop-distribution.c (destroy_loop): Process blocks in
+	correct order.
+
 2019-06-03  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
 
 	PR target/88837

gcc/testsuite/ChangeLog

+2019-06-03  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/90716
+	* gcc.dg/guality/pr90716.c: New testcase.
+
 2019-06-03  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
 
 	PR target/88837

gcc/testsuite/gcc.dg/guality/pr90716.c

+/* { dg-do run } */
+/* { dg-options "-g" } */
+
+void __attribute__((noinline))
+optimize_me_not ()
+{
+  __asm__ volatile ("" : : : "memory");
+}
+int a[7][8];
+int main()
+{
+  int b, j;
+  b = 0;
+  for (; b < 7; b++) {
+      j = 0;
+      for (; j < 8; j++)
+	a[b][j] = 0;
+  }
+  /* j may very well be optimized out, so we cannot test for j == 8.
+     Instead test j + 1 which will make the test UNSUPPORTED if i
+     is optimized out.  Since the test previously had wrong debug
+     with j == 0 this is acceptable.  */
+  optimize_me_not(); /* { dg-final { gdb-test . "j + 1" "9" } } */
+  return 0;
+}

gcc/tree-loop-distribution.c

@@ -1104,15 +1104,13 @@ destroy_loop (struct loop *loop)
 
   gimple_stmt_iterator dst_gsi = gsi_after_labels (exit->dest);
   bool safe_p = single_pred_p (exit->dest);
-  i = nbbs;
-  do
+  for (unsigned i = 0; i < nbbs; ++i)
     {
       /* We have made sure to not leave any dangling uses of SSA
          names defined in the loop.  With the exception of virtuals.
 	 Make sure we replace all uses of virtual defs that will remain
 	 outside of the loop with the bare symbol as delete_basic_block
 	 will release them.  */
-      --i;
       for (gphi_iterator gsi = gsi_start_phis (bbs[i]); !gsi_end_p (gsi);
 	   gsi_next (&gsi))
 	{
@@ -1147,7 +1145,6 @@ destroy_loop (struct loop *loop)
 	    gsi_next (&gsi);
 	}
     }
-  while (i != 0);
 
   redirect_edge_pred (exit, src);
   exit->flags &= ~(EDGE_TRUE_VALUE|EDGE_FALSE_VALUE);