Integer constant multiplication on Alpha

[Falk Hueffner <falk dot hueffner at student dot uni-tuebingen dot de>]

Hi,

I noticed gcc optimizes multiplications with integers quite good,
which is nice, but I have a few questions :)

* Where in the code does this happen? I looked quite hard, but
  couldn't find it.

* Why isn't this disabled on -Os?

* The code seems slightly subobtimal sometimes:

int foo(int x) {
    return 6*x;
}

yields

        s4subq $16,$16,$0
        addq $0,$0,$0
        addl $0,$31,$0
        ret $31,($26),1

with gcc 2.95.4 (Debian prerelease). What does that addl $0,$31,$0 do?
It looks like a sign extension, but the same could be achieved by just
using addl...

Also gcc 3.0 introduces a redundant mov:

        mov $16,$1
        s4subq $1,$1,$2
        addq $2,$2,$1
        addl $1,$31,$0
        ret $31,($26),1

where could I look to check where this comes from?

        Falk