Re: [PATCH] Assert on invalid bitmap iterations

[Bernd Schmidt]

On 10/07/2016 09:20 AM, Richard Biener wrote:
Index: gcc/sched-deps.c
===================================================================
--- gcc/sched-deps.c    (revision 240829)
+++ gcc/sched-deps.c    (working copy)
@@ -3992,8 +3992,14 @@ remove_from_deps (struct deps_desc *deps
   removed = remove_from_dependence_list (insn, 
&deps->last_pending_memory_flush);
   deps->pending_flush_length -= removed;
+  unsigned to_clear = -1U;
   EXECUTE_IF_SET_IN_REG_SET (&deps->reg_last_in_use, 0, i, rsi)
     {
+      if (to_clear != -1U)
+       {
+         CLEAR_REGNO_REG_SET (&deps->reg_last_in_use, to_clear);
+         to_clear = -1U;
+       }
       struct deps_reg *reg_last = &deps->reg_last[i];
       if (reg_last->uses)
        remove_from_dependence_list (insn, &reg_last->uses);
@@ -4005,8 +4011,10 @@ remove_from_deps (struct deps_desc *deps
        remove_from_dependence_list (insn, &reg_last->clobbers);
       if (!reg_last->uses && !reg_last->sets && !reg_last->implicit_sets
          && !reg_last->clobbers)
-        CLEAR_REGNO_REG_SET (&deps->reg_last_in_use, i);
+       to_clear = i;
     }
+  if (to_clear != -1U)
+    CLEAR_REGNO_REG_SET (&deps->reg_last_in_use, to_clear);

That looks pretty bad. What's the issue, we can't clear the current bit 
while iterating over a bitmap? Is that fixable - it seems like something 
people are likely to want to do?

Here, if necessary I'd prefer we create a to_clear bitmap and perform an 
and_compl operation after the loop.


Bernd