On Thu, Dec 17, 2015 at 11:04 AM, Nanley Chery <nanleych...@gmail.com> wrote:
> On Thu, Dec 17, 2015 at 12:05:46PM +0100, Glenn Kennard wrote:
>> On Wed, 16 Dec 2015 20:57:51 +0100, Nanley Chery <nanleych...@gmail.com>
>> wrote:
>>
>> >From: Nanley Chery <nanley.g.ch...@intel.com>
>> >
>> >Commit 64880d073ab21ae1abad0c049ea2d6a1169a3cfa consolidated two
>> >DIV_ROUND_UP() definitions to one, but chose the more
>> >compute-intensive version in the process. Use the simpler version
>> >instead. Reduces .text size by 1360 bytes.
>> >
>> >Output of `size lib/i965_dri.so`:
>> > text data bss dec hex filename
>> > 7850440 219264 27240 8096944 7b8cb0 lib/i965_dri.so (before)
>> > 7849080 219264 27240 8095584 7b8760 lib/i965_dri.so (after)
>> >
>> >Cc: Axel Davy <axel.d...@ens.fr>
>> >Signed-off-by: Nanley Chery <nanley.g.ch...@intel.com>
>> >---
>> > src/util/macros.h | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> >diff --git a/src/util/macros.h b/src/util/macros.h
>> >index 0c8958f..53a98a0 100644
>> >--- a/src/util/macros.h
>> >+++ b/src/util/macros.h
>> >@@ -211,6 +211,6 @@ do { \
>> > #endif
>> >/** Compute ceiling of integer quotient of A divided by B. */
>> >-#define DIV_ROUND_UP( A, B ) ( (A) % (B) == 0 ? (A)/(B) : (A)/(B)+1 )
>> >+#define DIV_ROUND_UP(A, B) (((A) + (B) - 1) / (B))
>> >#endif /* UTIL_MACROS_H */
>>
>> I'll point out that these are not equivalent, one can overflow and the other
>> doesn't. You
>> probably want to check if the call sites have sufficient checks for that
>> before
>> substituting one for the other.
>>
>
> Good point. As I mentioned in another email, I'll leave the current
> macro untouched.
I think the chances of us relying on overflow behavior are exceedingly
small, and nearly all uses of DIV_ROUND_UP are in the i965 driver. I
think it's sufficiently safe to go ahead with the patch (but I am
still interested to know about your compiler and CFLAGS).
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