[PATCH] Fix PR80713

[Richard Biener]

The following fixes up my earlier change in PRE for fallout with the
intricate interaction of the two "DCE" algorithms in PRE...

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2017-05-12  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/80713
        * tree-ssa-pre.c (remove_dead_inserted_code): Clear
        inserted_exprs bit for not removed stmts.

        * gcc.dg/torture/pr80713.c: New testcase.

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c  (revision 247952)
+++ gcc/tree-ssa-pre.c  (working copy)
@@ -4947,8 +4947,14 @@ remove_dead_inserted_code (void)
        }
     }
 
+  unsigned int to_clear = -1U;
   EXECUTE_IF_SET_IN_BITMAP (inserted_exprs, 0, i, bi)
     {
+      if (to_clear != -1U)
+       {
+         bitmap_clear_bit (inserted_exprs, to_clear);
+         to_clear = -1U;
+       }
       t = SSA_NAME_DEF_STMT (ssa_name (i));
       if (!gimple_plf (t, NECESSARY))
        {
@@ -4969,7 +4975,14 @@ remove_dead_inserted_code (void)
              release_defs (t);
            }
        }
+      else
+       /* eliminate_fini will skip stmts marked for removal if we
+          already removed it and uses inserted_exprs for this, so
+          clear those we didn't end up removing.  */
+       to_clear = i;
     }
+  if (to_clear != -1U)
+    bitmap_clear_bit (inserted_exprs, to_clear);
   BITMAP_FREE (worklist);
 }
 
Index: gcc/testsuite/gcc.dg/torture/pr80713.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr80713.c      (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr80713.c      (working copy)
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+
+int a, b, d, e, f;
+int *c;
+void g()
+{
+  for (;;)
+    {
+      if (*c) {
+         int h;
+         *c = &h;
+      } else
+       b = 0;
+      if (f)
+       *c = g;
+      else
+       for (; a; a++)
+         for (;;) {
+             if (d)
+               break;
+             c = e;
+         }
+    }
+}