32-bit integer multiplication.txt

来自「里面是比较经典的汇编例子程序」· 文本 代码 · 共 27 行

32-Bit Integer Multiplication
;
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; This routine multiplies two 32-bit signed integers
; resulting; in a 64-bit product. The operands are fetched
; from data memory and the result is written back to data
; memory.
; Data Storage:
; X1,X0 32-bit operand
; Y1,Y0 32-bit operand
; W3,W2,W1,W0 64-bit product
; Entry Conditions:
; SXM = 1, OVM = 0
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STM #X0,AR2 		;AR2 = X0 addr
STM #Y0,AR3 		;AR3 = Y0 addr
LD *AR2,T 		;T = X0
MPYU *AR3+,A 		;A = X0*Y0
STL A,@W0 		;save W0
LD A,–16,A 		;A = A >> 16
MACSU *AR2+,*AR3–,A 	;A = X0*Y0>>16 + X0*Y1
MACSU *AR3+,*AR2,A 	;A = X0*Y0>>16 + X0*Y1 + X1*Y0
STL A,@W1 		;save W1
LD A,–16,A 		;A = A >> 16
MAC *AR2,*AR3,A 	;A = (X0*Y1 + X1*Y0)>>16 + X1*Y1
STL A,@W2 		;save W2
STH A,@W3 		;save W3