Intel 64 and IA-32 Architectures Software Developers Manual Volume 1, Basic Architecture

Vol. 1 7-1
CHAPTER 7
PROGRAMMING WITH
GENERAL-PURPOSE INSTRUCTIONS
General-purpose (GP) instructions are a subset of the IA-32 instructions that repre-
sent the fundamental instruction set for the Intel IA-32 processors. These instruc-
tions were introduced into the IA-32 architecture with the first IA-32 processors (the
Intel 8086 and 8088). Additional instructions were added to the general-purpose
instruction set in subsequent families of IA-32 processors (the Intel 286, Intel386,
Intel486, Pentium, Pentium Pro, and Pentium II processors).
Intel 64 architecture further extends the capability of most general-purpose instruc-
tions so that they are able to handle 64-bit data in 64-bit mode. A small number of
general-purpose instructions (still supported in non-64-bit modes) are not supported
in 64-bit mode.
General-purpose instructions perform basic data movement, memory addressing,
arithmetic and logical, program flow control, input/output, and string operations on a
set of integer, pointer, and BCD data types. This chapter provides an overview of the
general-purpose instructions. See Intel® 64 and IA-32 Architectures Software Devel-
oper’s Manual, Volumes 3A & 3B, for detailed descriptions of individual instructions.
7.1 PROGRAMMING ENVIRONMENT FOR GP
INSTRUCTIONS
The programming environment for the general-purpose instructions consists of the
set of registers and address space. The environment includes the following items:
• General-purpose registers — Eight 32-bit general-purpose registers (see
Section 3.4.1, “General-Purpose Registers”) are used in non-64-bit modes to
address operands in memory. These registers are referenced by the names EAX,
EBX, ECX, EDX, EBP, ESI EDI, and ESP.
• Segment registers — The six 16-bit segment registers contain segment
pointers for use in accessing memory (see Section 3.4.2, “Segment Registers”).
These registers are referenced by the names CS, DS, SS, ES, FS, and GS.
• EFLAGS register — This 32-bit register (see Section 3.4.3, “EFLAGS Register”)
is used to provide status and control for basic arithmetic, compare, and system
operations.
• EIP register — This 32-bit register contains the current instruction pointer (see
Section 3.4.3, “EFLAGS Register”).
General-purpose instructions operate on the following data types. The width of valid
data types is dependent on processor mode (see Chapter 4):
• Bytes, words, doublewords