Hi Tim,
> 86 0030 4AAE 0008 tst.l 8(%fp)
> 87 0034 56C0 sne %d0
> 88 0036 4E5E unlk %fp
> 89 .cfi_offset 14, -8
> 90 0038 7100 mvs.b %d0,%d0
> 91 003a 4480 neg.l %d0
> 92 003c 4E75 rts
I don't know 68000/Coldfire so I'm enjoying this. :-)
tst.l 8(%fp) ; compare x to 0.
sne %d0 ; if x != 0: d0 = 0xff.
unlk %fp ; prepare for return.
mvs.b %d0,%d0 ; sign-extend the byte in d0 to be 32-bit.
neg.l %d0 ; d0 = 0 - d0. 0 stays 0, -1 becomes 1.
rts ; return.
> At first glance not sure why the mvs.b is necessary.
I agree. It could be (* marks change)
tst.l 8(%fp) ; compare x to 0.
sne %d0 ; if x != 0: d0 = 0xff.
unlk %fp ; prepare for return.
* neg.b %d0 ; d0 = 0 - d0. 0 stays 0, -1 becomes 1.
rts ; return.
if the neg.l became a neg.b. I guess it's because it knows it's
returning a 32-bit int and doesn't see it can stick with 8-bit.
Cheers,
Ralph.
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