文章目錄

• MUL
• MLA
• SMULL
• SMLAL
• UMULL
• UMLAL

ARM有兩類乘法指令：一類指令的操作結果為32位，所以叫32位乘法指令；另一類的操作結果位64位，所以叫64位乘法指令。

為了運算高效，乘法指令要求所有操作數都位于寄存器中，所以ARM乘法指令無需指定尋址方式。

ARM共有如下乘法指令：

助記符說明實現邏輯

MUL	32位乘法指令	Rd = Rm * Rs
MLA	32位帶加數的乘法指令	Rd = Rm * Rs + Rn
SMULL	64位有符號數乘法指令	RdHi = (Rm * Rs)[63:32]; RdLo = (Rm * Rs)[31:0];
SMLAL	64位帶加數的有符號數乘法指令	RdLo = (Rm * Rs)[31:0] + RdLo; RdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo);
UMULL	64位無符號數乘法指令	RdHi = (Rm * Rs)[63:32]; RdLo = (Rm * Rs)[31:0];
UMLAL	64位帶加數的無符號數乘法指令	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) thenRd = (Rm * Rs)[31:0]if S == 1 thenN Flag = Rd[31]Z Flag = if Rd == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

MLA

MLA{<cond>}{S} <Rd>, <Rm>, <Rs>, <Rn>if ConditionPassed(cond) thenRd = (Rm * Rs + Rn)[31:0]if S == 1 thenN Flag = Rd[31]Z Flag = if Rd == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

SMULL

SMULL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>if ConditionPassed(cond) thenRdHi = (Rm * Rs)[63:32] // 計算結果的高32位RdLo = (Rm * Rs)[31:0] // 計算結果的低32位if S == 1 thenN Flag = RdHi[31]Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

SMLAL

SMLAL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>if ConditionPassed(cond) thenRdLo = (Rm * Rs)[31:0] + RdLoRdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo)if S == 1 thenN Flag = RdHi[31]Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

UMULL

UMULL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>if ConditionPassed(cond) thenRdHi = (Rm * Rs)[63:32]RdLo = (Rm * Rs)[31:0]if S == 1 thenN Flag = RdHi[31]Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

UMLAL

UMLAL{<cond>}{S} <RdLo>, <RdHi>, <Rm>, <Rs>, <Rn>if ConditionPassed(cond) thenRdLo = (Rm * Rs)[31:0] + RdLoRdHi = (Rm * Rs)[63:32] + RdHi + CarryFrom((Rm * Rs)[31:0] + RdLo)if S == 1 thenN Flag = RdHi[31]Z Flag = if RdHi == 0 and RdLo == 0 then 1 else 0C Flag = unaffectedV Flag = unaffected

總結

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