At Fri, 1 Apr 2005 21:56:03 -0500, Daniel Jacobowitz wrote: > > > it will not disable SSE. > > > > SSE is masked off by default, I asked for how to enable it. > > Build a glibc which considers it a relevant capability for library > selection. It's just a matter of setting the bit in HWCAP_IMPORTANT.
Note that another way is to use LD_HWCAP_MASK. LD_HWCAP_MASK overwrites the default HWCAP_IMPORTANT mask in rtld.c. However it just changes HWCAP value - so we need to make ld.so to search library path using some library search path modifying environment variable (ex: LD_LIBRARY_PATH). I think the simple shell script wrapper controlling HWCAP_MASK can achieve the original request by Bastian. The script also controls to set LD_ASSUME_KERNEL automatically from the current running kernel version. If an application (ex: UML and Xen) is sensitive to the glibc's tls and so on, it should be wrapped by a script, and the script calls (or includes) our wrapper script that controls HWCAP_MASK. BTW, I think various hwcap like "sse" should not be encouraged to use by users and developers. Sometimes speed-crazy developers want to play with optimized libraries only changing gcc optimized options. However in most case they don't provide any performance gain value. I also think it's the same situation with the glibc optimized libraries (alpha, sparcv9/v9b) (note that i686 optimized library has the exact merit). If gcc will have good support of automatic optimization using SSE that sometimes gets much performance gain (ex: intel compiler -ip option), it's nice to consider such generic searching path mechanism for "sse". However, that possibly degrades the precision of the computed result. So we should be care to enable SSE everytime as well. Regards, -- gotom -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
