Module rex

Encodes instructions in the standard x86 encoding mode. This is called IA-32E mode in the Intel manuals but corresponds to the addition of the REX-prefix format (hence the name of this module) that allowed encoding instructions in both compatibility mode (32-bit instructions running on a 64-bit OS) and in 64-bit mode (using the full 64-bit address space).

For all of the routines that take both a memory-or-reg operand (sometimes called “E” in the Intel documentation, see the Intel Developer’s manual, vol. 2, section A.2) and a reg-only operand (“G” in Intel-ese), the order is always G first, then E. The term “enc” in the following means “hardware register encoding number”.

Structs

• RexFlags
  A small bit field to record a REX prefix specification:

Enums

• LegacyPrefixes
  We may need to include one or more legacy prefix bytes before the REX prefix. This enum covers only the small set of possibilities that we actually need.
• OpcodeMap
  Allows using the same opcode byte in different “opcode maps” to allow for more instruction encodings. See appendix A in the Intel Software Developer’s Manual, volume 2A, for more details.

Functions

• encode_modrm
  Encode the ModR/M byte.