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3-6 Vol. 2A
INSTRUCTION SET REFERENCE, A-M
• Sreg — A segment register. The segment register bit assignments are ES = 0,
CS = 1, SS = 2, DS = 3, FS = 4, and GS = 5.
• m32fp, m64fp, m80fp — A single-precision, double-precision, and double
extended-precision (respectively) floating-point operand in memory. These
symbols designate floating-point values that are used as operands for x87 FPU
floating-point instructions.
• m16int, m32int, m64int — A word, doubleword, and quadword integer
(respectively) operand in memory. These symbols designate integers that are
used as operands for x87 FPU integer instructions.
• ST or ST(0) — The top element of the FPU register stack.
• ST(i) — The i
th
element from the top of the FPU register stack (i ← 0 through 7).
• mm — An MMX register. The 64-bit MMX registers are: MM0 through MM7.
• mm/m32 — The low order 32 bits of an MMX register or a 32-bit memory
operand. The 64-bit MMX registers are: MM0 through MM7. The contents of
memory are found at the address provided by the effective address computation.
• mm/m64 — An MMX register or a 64-bit memory operand. The 64-bit MMX
registers are: MM0 through MM7. The contents of memory are found at the
address provided by the effective address computation.
• xmm — An XMM register. The 128-bit XMM registers are: XMM0 through XMM7;
XMM8 through XMM15 are available using REX.R in 64-bit mode.
• xmm/m32— An XMM register or a 32-bit memory operand. The 128-bit XMM
registers are XMM0 through XMM7; XMM8 through XMM15 are available using
REX.R in 64-bit mode. The contents of memory are found at the address provided
by the effective address computation.
• xmm/m64 — An XMM register or a 64-bit memory operand. The 128-bit SIMD
floating-point registers are XMM0 through XMM7; XMM8 through XMM15 are
available using REX.R in 64-bit mode. The contents of memory are found at the
address provided by the effective address computation.
• xmm/m128 — An XMM register or a 128-bit memory operand. The 128-bit XMM
registers are XMM0 through XMM7; XMM8 through XMM15 are available using
REX.R in 64-bit mode. The contents of memory are found at the address provided
by the effective address computation.
3.1.1.3 64-bit Mode Column in the Instruction Summary Table
The “64-bit Mode” column indicates whether the opcode sequence is supported in
64-bit mode. The column uses the following notation:
• Valid — Supported.
• Invalid — Not supported.
• N.E. — Indicates an instruction syntax is not encodable in 64-bit mode (it may
represent part of a sequence of valid instructions in other modes).