This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH]: New sparse bitmap implementation
On 3/20/07, Eric Botcazou <ebotcazou@libertysurf.fr> wrote:
> * ebitmap.h: New file
> * ebitmap.c: New file
Minor nits:
--- gcc/ebitmap.c (revision 0)
+++ gcc/ebitmap.c (revision 0)
@@ -0,0 +1,1019 @@
+/* Sparse array-based bitmaps.
+ Copyright (C) 2006 Free Software Foundation, Inc.
+ Contributed by Daniel Berlin <dberlin@dberlin.org>
--- gcc/ebitmap.h (revision 0)
+++ gcc/ebitmap.h (revision 0)
@@ -0,0 +1,162 @@
+/* Sparse array based bitmaps.
+ Copyright (C) 2007 Free Software Foundation, Inc.
The same copyright date would probably be expected.
Whoops
+ in words that are all zero, the time to test is O(1). For bits
+ in words that exist, it requires it will require O(n/sizeof(word))
Pasto.
Fixed.
+ easily vectorized. They are all O(number of words) + O(number of
+ bits that may end up in the destination), as the approriate
Typo in last word.
Fixed
/* #define EBITMAP_DEBUGGING */
Why not predicate the debugging code on --enable-checking=misc?
It's *incredibly* expensive.
In most cases, it duplicate the entire operation non-sparsely, bit by bit.
In the into versions, it also copies the entire destination bitmap so
it can do the operation non-sparsely to verify results.
It's also code that only ever needs to be run if you are changing the
implementation.
Our bitmap/sbitmap code has had such a low rate of change (we usually
have one change every few *years*) that it seems "not worth it" even
for =misc.
I wish every new file had so thorough a head comment!
Thanks.
That was Steven Bosscher's idea, who reminded me that nobody else had
any idea how the data structure actually looked and operated :)
--
Eric Botcazou