Instruction prefixes

In this section:

• Introduction
• The execution environment
• The CODE/EDOC facility
• Mixing of Intel 32-bit Assembler and Fortran
• Labels
• Referencing Fortran variables
• Literals
• Halfword and byte forms of instructions
• Using the coprocessor
• Instruction prefixes
• Other assembler facilities
• Other machine-level facilities
• Error messages
• 64-bit assembler

The following prefixes are available as pseudo instructions coded on the line above :

REP
REPE
REPNE
FS ;Appends the FS: prefix
GS ;Appends the GS: prefix

For example:

FS ;Source operand from FS
REP
MOVSB

or

MOV FS:0,ESP%

would be coded as

FS
MOV 0,ESP%

Other prefixes are rarely needed, however they are available using the DB pseudo instruction to code an arbitrary byte. For example the CS: prefix could be coded as:

DB Z'0E'