David Given made top for PowerPC. Copy the asopt phase (running top)
from linuxppc to osxppc.
Remove CC_ALIGN=-Vr to become compatible with Apple's gcc. Apple uses
left adjustment for bitfields; the first bitfield is on the left side
(the big end), not the right side.
Remove unused variables C_LIB and OLD_C_LIB; the file libc-ansi.a
doesn't exist.
Change MACHOPT_F from -m10 to -m3. This means to use no more than 3
adds and shifts to optimize a multiply by a constant. I pick -m3
because -m4 can use too many instructions. At -m4, the compiler
rewrites
n * 14
as
s = n << 1
(s << 3) + (0 - s)
This means (n * 16 - n * 2), but even at ack -O6, the compiler doesn't
rewrite (a + (0 - b)) as (a - b). The compiler emits 5 instructions:
2 of rlinmw for 2 left shifts, then addi to load 0 in a register, subf
to subtract from that 0, then add. These 5 instructions cost 5 cycles
on the MPC7450, using the cycle counts from mach/powerpc/ncg/table.
At -m3, (n * 14) becomes 2 instructions: addi to load 14 in a register
and mullw to multiply. This also costs 5 cycles (because mullw costs
4 cycles), but uses less space.
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