On Fri, 7 Oct 2016, Richard Biener wrote:
> I think the main issue is that it is not documented what is safe to do
> (and what are the results) when you modify a bitmap while you are
> iterating over it.
Does the following look ok?
Thanks,
Richard.
2016-10-07 Richard Biener <rguent...@suse.de>
* bitmap.h: Document constraints on bitmap modification while
iterating over it.
Index: gcc/bitmap.h
===================================================================
--- gcc/bitmap.h (revision 240859)
+++ gcc/bitmap.h (working copy)
@@ -755,6 +755,18 @@ bmp_iter_and_compl (bitmap_iterator *bi,
}
}
+/* If you are modifying a bitmap you are currently iterating over you
+ have to ensure to
+ - never remove the current bit;
+ - if you set or clear a bit before the current bit this operation
+ will not affect the set of bits you are visiting during the iteration;
+ - if you set or clear a bit after the current bit it is unspecified
+ whether that affects the set of bits you are visiting during the
+ iteration.
+ If you want to remove the current bit you can delay this to the next
+ iteration (and after the iteration in case the last iteration is
+ affected). */
+
/* Loop over all bits set in BITMAP, starting with MIN and setting
BITNUM to the bit number. ITER is a bitmap iterator. BITNUM
should be treated as a read-only variable as it contains loop
