indexing - x86 64 AT&T , moving part of register into another register -

i'd move 1 byte register rdx register rbx, this:

mov %rdx , (%rbx,%r15,1) 

where rdx contains 0x33 ,r15 index , rbx contains 0 @ start.

i have tried using method in many ways , ending sigsegv error. in end going create rbx register contain array of next rdx values

you can shift bytes in 1 @ time, this:

; calculate first dl ... mov  %dl,%bl ; calculate next dl ... shlq $8,%rbx mov  %dl,%bl ; calculate next dl ... shlq $8,%rbx mov  %dl,%bl 

etc. assumes want first byte in msb, , last byte in lsb. revesre order bit more complicated, not much.