; Return in registers RDX:RAX the double word in registers RSI:RDI with
; reversed bit order.

option prologue:none, epilogue:none
.code
bitr128	proc
_bitr128 proc
	MOV	ECX,64	; Initialise the bit counter
	SHL	RSI,1	; Get the most significant (highest) bit in CF
	.repeat
		RCR	RDI,1; Put the highest bit from CF, get the lowest
		RCL	RSI,1; Put the lowest bit from CF, get the highest
	.untilcxz	; Next iteration of the loop
	XCHG	RAX,RDI
	MOV	RDX,RSI	; Return the double word in RDX:RAX
	RET
_bitr128 endp
bitr128	endp
end