On 2016-05-05 06:07 AM, Amaury Pouly wrote:
The removal of #ifdef CLZ_HWI and #ifdef CTZ_HWI code is not needed
for successful building. That changes floor_log2() and exact_log2()
from code based on one of the __builtin_clz functions to alternative
code. I'm left wondering what is the reason for that change.
My old compiler, a new one with this patch, and a new one without
the #ifdef code removal all produce the exact same ipodvideo
rockbox.bin.
The reason of the change is because the newer GCC compile in C11 mode by
default (instead of C89), which has slightly stricter rules on function
redefinition. This patches only makes sure the code compiles in C11, but
otherwise the compiler is exactly the same. You can find more
information about this patch here:
https://gcc.gnu.org/ml/gcc-patches/2009-06/msg01249.html
I understand now. The removal of #ifdef CLZ_HWI and #ifdef CTZ_HWI code
simply removes code which will never be compiled due to conditionals.
Both floor_log2() and exact_log2() used to be inside an "#if GCC_VERSION
< 3004 || !defined (__cplusplus)" block. After the patch it becomes just
a #if GCC_VERSION < 3004 block. In toplev.h, CLZ_HWI and CTZ_HWI are
only #defined if GCC_VERSION >= 3004.
This looks good and the gcc-patches message says it got committed there
also. The patch should definitely be used.
(Resending this to rockbox-dev separately because I forgot to use reply
to all the first time.)
