[vlc-devel] LTO Support for VLC source code!

[xxcv]

On 25/09/2010 2:41 PM, Rémi Denis-Courmont wrote:
>     Hello,
>
> On Friday 24 September 2010, xxcv wrote:
>> Hello All!!
>>
>> Yesterday I succeeded in compilation VLC 1.1 Branch with new GCC 4.5
>> feature LTO -flto.
>> I was overwhelmed !!!
>
> That's great... but what's lto anyway?
>
>
http://en.wikipedia.org/wiki/Interprocedural_optimization
http://en.wikipedia.org/wiki/Link-time_optimization
http://gcc.gnu.org/wiki/LinkTimeOptimization
http://gcc.gnu.org/gcc-4.5/changes.html (A new link-time optimizer has 
been added (-flto).)

Also I was trying to put some support in configure like this, which, I 
saw how ffast-math was done.
It needed to be put into the env variable ldflags as well.

diff --git a/configure.ac b/configure.ac
index 9ff9b4c..a5ed53a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1046,6 +1046,15 @@ if test "${ac_cv_c_o0}" != "no"; then
      CFLAGS_NOOPTIM="${CFLAGS_NOOPTIM} -O0"
  fi

+dnl Check for -flto
+AC_CACHE_CHECK([if \$CC accepts -flto],
+    [ac_cv_c_lto],
+    [CFLAGS="${CFLAGS_save} -flto"
+     AC_TRY_COMPILE([],,ac_cv_c_lto=yes, ac_cv_c_lto=no)])
+if test "${ac_cv_c_lto}" != "no"; then
+    CFLAGS_OPTIM_SPEED="${CFLAGS_OPTIM_SPEED} -flto"
+fi
+
  dnl Check for -ffast-math
  AC_CACHE_CHECK([if \$CC accepts -ffast-math],
      [ac_cv_c_fast_math],


Regards,

-- 
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