assembly - Fourth parameter on ARM SUBtract instruction -


can explain/confirm (particularly sub line) me:

cmp align,#2 cmpne align,#5 cmpne align,#8 subeq xpos,xpos,width,lsr#1

i thinking might equivilant c code:

if ((align==2) || (align==5) || (align==8)) {   xpos -= width >> 1; }

i have found documentation don't understand forth parameter, imm12. says:

the sub instruction subtracts value of operand2 or imm12 value in rn.

your assumption code looks correct me.

but don't understand forth parameter, imm12

the fourth parameter not imm12, rather a shift operation on width (which assume alias 1 of general purpose registers).


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