ARM有两类乘法指令:一类指令的操作结果为32位,所以叫32位乘法指令;另一类的操作结果位64位,所以叫64位乘法指令。
为了运算高效,乘法指令要求所有操作数都位于寄存器中,所以ARM乘法指令无需指定寻址方式。
ARM共有如下乘法指令:
助记符 | 说明 | 实现逻辑 |
---|---|---|
MUL | 32位乘法指令 | Rd = Rm * Rs |
MLA | 32位带加数的乘法指令 | Rd = Rm * Rs + Rn |
SMULL | 64位有符号数乘法指令 | RdHi = (Rm * Rs)[63:32]; RdLo = (Rm * Rs)[31:0]; |
SMLAL | 64位带加数的有符号数乘法指令 | RdLo = (Rm * Rs)[31:0] + RdLo; RdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo); |
UMULL | 64位无符号数乘法指令 | RdHi = (Rm * Rs)[63:32]; RdLo = (Rm * Rs)[31:0]; |
UMLAL | 64位带加数的无符号数乘法指令 | RdLo = (Rm * Rs)[31:0] + RdLo; RdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo); |
MUL
MUL{<cond>}{S} <Rd>, <Rm>, <Rs>
if ConditionPassed(cond) then
Rd = (Rm * Rs)[31:0]
if S == 1 then
N Flag = Rd[31]
Z Flag = if Rd == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
MLA
MLA{<cond>}{S} <Rd>, <Rm>, <Rs>, <Rn>
if ConditionPassed(cond) then
Rd = (Rm * Rs + Rn)[31:0]
if S == 1 then
N Flag = Rd[31]
Z Flag = if Rd == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
SMULL
SMULL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>
if ConditionPassed(cond) then
RdHi = (Rm * Rs)[63:32] // 计算结果的高32位
RdLo = (Rm * Rs)[31:0] // 计算结果的低32位
if S == 1 then
N Flag = RdHi[31]
Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
SMLAL
SMLAL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>
if ConditionPassed(cond) then
RdLo = (Rm * Rs)[31:0] + RdLo
RdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo)
if S == 1 then
N Flag = RdHi[31]
Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
UMULL
UMULL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>
if ConditionPassed(cond) then
RdHi = (Rm * Rs)[63:32]
RdLo = (Rm * Rs)[31:0]
if S == 1 then
N Flag = RdHi[31]
Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
UMLAL
UMLAL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>
if ConditionPassed(cond) then
RdLo = (Rm * Rs)[31:0] + RdLo
RdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo)
if S == 1 then
N Flag = RdHi[31]
Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0
C Flag = unaffected
V Flag = unaffected
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