大名鼎鼎的keil51,竟然實(shí)現(xiàn)不了雙字節(jié)乘以雙字節(jié)的簡(jiǎn)單乘法運(yùn)算.
我們都知道兩個(gè)無(wú)符號(hào)雙字節(jié)相乘,結(jié)果是一個(gè)無(wú)符號(hào)的四字節(jié),但是keil51就認(rèn)為是相乘的結(jié)果是一個(gè)雙字節(jié),豈有不錯(cuò)之理?

   286:         along= SetLengthA * FreqValueA;
C:0x1000    78C2     MOV      R0,#FreqValueA(0xC2)
C:0x1002    E6       MOV      A,@R0
C:0x1003    FC       MOV      R4,A
C:0x1004    08       INC      R0
C:0x1005    E6       MOV      A,@R0
C:0x1006    FD       MOV      R5,A
C:0x1007    78C7     MOV      R0,#SetLengthA(0xC7)
C:0x1009    E6       MOV      A,@R0
C:0x100A    FE       MOV      R6,A
C:0x100B    08       INC      R0
C:0x100C    E6       MOV      A,@R0
C:0x100D    FF       MOV      R7,A
C:0x100E    12072D   LCALL    C?IMUL(C:072D)
C:0x1011    E4       CLR      A
C:0x1012    8F37     MOV      0x37,R7
C:0x1014    8E36     MOV      0x36,R6
C:0x1016    F535     MOV      0x35,A
C:0x1018    F534     MOV      0x34,A
這其中的那個(gè)乘法子程序,我分析過(guò)了,就是:int=int*int
哪怕我用一個(gè)long型變量來(lái)接收結(jié)果,編譯器也是調(diào)用這個(gè)子程序,這顯然是錯(cuò)誤的