What is CMP x86?
The CMP instruction compares two operands. This instruction basically subtracts one operand from the other for comparing whether the operands are equal or not.
What does CMP instruction do?
The CMP instruction subtracts the value of Operand2 from the value in Rn . This is the same as a SUBS instruction, except that the result is discarded. The CMN instruction adds the value of Operand2 to the value in Rn . This is the same as an ADDS instruction, except that the result is discarded.
What does CMP mean in assembly?
Operands
Compare Two Operands (cmp) (IA-32 Assembly Language Reference Manual)
Where does CMP Store result?
The difference is not stored anywhere. However, the flags register is updated and can be used in a conditional jump, like jump-if-equal ( JE ), most often as the next instruction after the cmp .
What is the EAX register?
eax. eax is a 32-bit general-purpose register with two common uses: to store the return value of a function and as a special register for certain calculations. It is technically a volatile register, since the value isn’t preserved. Instead, its value is set to the return value of a function before a function returns.
What is Lea Assembly?
lea — Load effective address. The lea instruction places the address specified by its first operand into the register specified by its second operand. Note, the contents of the memory location are not loaded, only the effective address is computed and placed into the register.
What does Inc do in assembly?
The INC instruction is used for incrementing an operand by one. It works on a single operand that can be either in a register or in memory.
Which flags are affected by CMP instruction?
CMP and TEST instructions affect flags only and do not store a result (these instruction are used to make decisions during program execution). These instructions affect these flags only: CF, ZF, SF, OF, PF, AF. ADD – add second operand to first.
What is RSB in arm?
The RSB instruction subtracts the value in Rn from the value of Operand2 . This is useful because of the wide range of options for Operand2 . In certain circumstances, the assembler can substitute one instruction for another.
Which flag are affected by CMP instruction?
CMP and TEST instructions affect flags only and do not store a result (these instruction are used to make decisions during program execution). These instructions affect these flags only: CF, ZF, SF, OF, PF, AF.
What is the CL register?
EBX,BX,BH,BL : Called the Base register It is used as a base pointer for memory access Gets some interrupt return values ECX,CX,CH,CL : Called the Counter register It is used as a loop counter and for shifts Gets some interrupt values EDX,DX,DH,DL : Called the Data register It is used for I/O port access, arithmetic.
What is Ja Assembly?
JA is used for jumping if the last “flag changing” instruction was on unsigned numbers. but on the other hand, JG is used for jumping if the last “flag changing” instruction was on signed numbers.
What is the CMP instruction used for?
The cmp instruction is used to perform comparison. It’s identical to the sub instruction except it does not affect operands.
What are the different types of x86 instructions?
Machine instructions generally fall into three categories: data movement, arithmetic/logic, and control-flow. In this section, we will look at important examples of x86 instructions from each category. This section should not be considered an exhaustive list of x86 instructions, but rather a useful subset.
What is the best assembly language for writing x86 machine code?
There are several different assembly languages for generating x86 machine code. The one we will use in CS216 is the Microsoft Macro Assembler (MASM) assembler. MASM uses the standard Intel syntax for writing x86 assembly code.
How many general purpose registers are there in a modern x86 processor?
Guide to Using Assembly in Visual Studio — a tutorial on building and debugging assembly code in Visual Studio Modern (i.e 386 and beyond) x86 processors have eight 32-bit general purpose registers, as depicted in Figure 1. The register names are mostly historical.