James wrote:
Hello,
Current CFLAGS="-O2 -march=i686 -pipe"
I want to add "-fomit-frame-pointer" to my
CFLAGS on an existing system that has been running
for months.
Is this safe or do I have to rebuild everything with
somelike "emerge -e" ?
Should it be avoided completely?
James
Hi,
I am not too good in English but I alway understood that:
|-fomit-frame-pointer|
Don't keep the frame pointer in a register for functions that don't
need one. This avoids the instructions to save, set up and restore
frame pointers; it also makes an extra register available in many
functions. *It also makes debugging impossible on some machines.*
On some machines, such as the VAX, this flag has no effect, because
the standard calling sequence automatically handles the frame
pointer and nothing is saved by pretending it doesn't exist. The
machine-description macro |FRAME_POINTER_REQUIRED| controls whether
a target machine supports this flag. See Register Usage
<http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gccint/Registers.html#Registers>.
Enabled at levels -O, -O2, -O3, -Os.
means, that fomit-frame-pointer is already active when -o ... is choose.
see
http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Optimize-Options.html#Optimize-Options
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