Question about cc flags in buildkernel

[Bernd Walter]

On Mon, Mar 07, 2005 at 09:07:01PM -0600, Kirk Strauser wrote:
> I'm building a kernel on a Cabriolet (EV45/275 MHz), and am a little curious
> about something in the make output.  My make.conf has these:
> 
>    CPUTYPE=ev45
>    CFLAGS= -O3 -pipe -fno-strict-aliasing -mieee
>    COPTFLAGS= -O3 -pipe -fno-strict-aliasing -mieee
> 
> and I'm seeing lines like:
> 
>    cc -c -O2 -pipe -fno-strict-aliasing -mieee -fno-strict-aliasing -mcpu=ev45 -mieee -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -fformat-extensions -std=c99 -nostdinc -I- -I. -I/usr/src/sys -I/usr/src/sys/contrib/dev/acpica -I/usr/src/sys/contrib/altq -I/usr/src/sys/contrib/ipfilter -I/usr/src/sys/contrib/pf -I/usr/src/sys/contrib/dev/ath -I/usr/src/sys/contrib/dev/ath/freebsd -I/usr/src/sys/contrib/ngatm -D_KERNEL -include opt_global.h -finline-limit=15000 --param inline-unit-growth=100 --param large-function-growth=1000 -mno-fp-regs -ffixed-8 -Wa,-mev6 -ffreestanding /usr/src/sys/alpha/alpha/genassym.c
> 
> The part that's confusing me is the "-Wa,-mev6".  What exactly does that
> refer to?  I couldn't find it in the "as" info page, but it looks at first
> glance like it's targetting an architecture that I don't have.  Am I
> misreading that?  If not, why did it select that?  Could this be why my
> EV45/275 seems to run like a Pentium 90?

This teaches the assembler to understand ev6 instructions.
It's done to allow building e.g. ev5 code, but still allow ev6
instructions in platform specific inline assembler for mixed target
kernels.
There is no speed influence by this option.

How did you compare speed?
If it's just from compile time, you shouldn't forget that gcc-3 is much
slower than the older gcc and that compiling for alpha is a much harder
job than compiling for i386.

-- 
B.Walter                   BWCT                http://www.bwct.de
bernd at bwct.de                                  info at bwct.de