Page 1 of 1
fcombine-regs
Posted: Sat Jan 06, 2007 4:56 pm
by piranha
What is fcombine-regs? I found this in the linux kernel 0.01 makefile.
thx
Posted: Sat Jan 06, 2007 5:09 pm
by Alboin
Ahem,
Code: Select all
Allow the combine pass to combine an instruction that
copies one register into another. This might or might
not produce better code when used in addition to -O. I
am interested in hearing about the difference this
makes.
This is from an archive of GCC 1.36's manual. It's no longer used. At least that's what my GCC tells me in the form of:
Code: Select all
cc1: error: unrecognized option `-fcombine-regs'
Posted: Sat Jan 06, 2007 5:10 pm
by piranha
For example:
gcc -fcombine-regs t.c -o t.o
i get it to say: unrecognized command line option "-fcombine-regs"
I don't know if this is the reason, but when I compile linux it has hundreds of errors.
Posted: Sat Jan 06, 2007 5:13 pm
by Alboin
No, I don't think the lack of -fcombine-regs should produce any errors, as it is just an optimization. (Yet, I could be wrong...
) However, the hundreds of errors might be coming from various changes that have occurred over 15 years in different tools....Maybe?
Posted: Sat Jan 06, 2007 8:09 pm
by Brynet-Inc
The original linux kernel was compiled under minix.
I remember seeing someone's site that made a patch or alternative release that is buildable on modern systems.
Can't remember where..