问题
While reading the Intel 64 and IA-32 Architectures Software Developer’s Manual, the operation section for the LEA instruction (load effective address) uses a calculation called EffectiveAddress(SRC) which is not defined anywhere else.
What is the definition of effective address and what does EffectiveAddress(SRC) do?
回答1:
Section 3.7.5 (Specifying an Offset) of the same document states:
The offset part of a memory address can be specified directly as a static value (called a displacement) or through an address computation made up of one or more of the following components:
- Displacement — An 8-, 16-, or 32-bit value.
- Base — The value in a general-purpose register.
- Index — The value in a general-purpose register.
- Scale factor — A value of 2, 4, or 8 that is multiplied by the index value.
The offset which results from adding these components is called an effective address. Each of these components can have either a positive or negative (2s complement) value, with the exception of the scaling factor.
EffectiveAddress calculates an effective address using:
Base + (Index*Scale) + Displacement
来源：https://stackoverflow.com/questions/36704481/what-is-an-effective-address