Basic Math Functions

• The carry and overflow flags are set relative to the data size used in the addition
• adc source, destination
• movl data+4, %ebx
• printf("%qd")

pushl 高位
pushl 低位

有符号数的加减是否影响 CF?

• NEG

NEG命令无论你是否为正负数，都会按照取反+1或用0减去这个数的二进制的办法去计算

• The carry flag was set when the result was less than zero

• SBB instruction utilizes the carry and overflow flags in multibyte subtractions to implement the borrow feature across data boundaries

• increment (INC) and decrement (DEC) an unsigned integer

• mul source

two unsigned integers
AL, AX, or EAX
DX:AX
EDX:EAX

• using indexed memory access

IMUL instruction can be used by both signed and unsigned integers, 
although you must be careful that the result does not use the most significant bit of the destination. For larger values, 
the IMUL instruction is only valid for signed integers

• imul source
• imul source, destination

source can be a 16- or 32-bit register or value in memory, and destination must be a 16- or 32-bit general-purpose register

• imul multiplier, source, destination

where multiplier is an immediate value, source is a 16- or 32-bit register or value in memory, and destination must be a general-purpose register

• div

dividend in AX, DX:AX, EDX:EAX
低位存储商

• idiv

only one format for the IDIV instruction
For signed integer division, the sign of the remainder is always the sign of the dividend

SAL (shift arithmetic left)
SHL (shift logical left)

sal destination
sal %cl, destination
sal shifter, destination

• destination operand can be an 8-, 16-, or 32-bit register or value in memory
• Any bits that are shifted out of the data size are first placed in the carry
  flag, and then dropped in the next shift

• SHR
• SAR

first moved to the carry flag, and then
shifted out

• ROL

• ROR

• RCL

• RCR

• AAA

• AAS

• AAM

• AAD

only AAD 用在 DIV 之前
都使用默认的 AL register

• Packed BCD arithmetic

• DAA: Adjusts the result of the ADD or ADC instructions
• DAS: Adjusts the result of the SUB or SBB instructions