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286 Instruction Latencies Appendix C
25112 Rev. 3.06 September 2005
Software Optimization Guide for AMD64 Processors
LEAVE (32 or 64 bit stack size) C9h Double 3
LES reg16/32, mem32/48 C4h mm-xxx-xxx VectorPath ~
LFS reg16/32, mem32/48 0Fh B4h VectorPath ~
LGDT mem16:32 0Fh 01h mm-010-xxx VectorPath 37
LGDT mem16:64 0Fh 01h mm-010-xxx VectorPath ~
LGS reg16/32, mem32/48 0Fh B5h VectorPath ~
LIDT mem16:32 0Fh 01h mm-011-xxx VectorPath 148
LIDT mem16:64 0Fh 01h mm-011-xxx VectorPath ~
LLDT mreg16 0Fh 00h 11-010-xxx VectorPath 34
LLDT mem16 0Fh 00h mm-010-xxx VectorPath 35
LMSW mreg16 0Fh 01h 11-100-xxx VectorPath 11
LMSW mem16 0Fh 01h mm-100-xxx VectorPath 12
LODS/LODSB mem8 ACh VectorPath 5 6
LODS/LODSW mem16 ADh VectorPath 5 6
LODS/LODSD mem32 ADh VectorPath 4 6
LODS/LODSQ mem64 ADh VectorPath ~ 6
LOOP disp8 E2h VectorPath 9/8 7
LOOPE/LOOPZ disp8 E1h VectorPath 9/8 7
LOOPNE/LOOPNZ disp8 E0h VectorPath 9/8 7
LSL reg16/32/64, mreg16/32 0Fh 03h 11-xxx-xxx VectorPath 21
LSL reg16/32/64, mem16/32 0Fh 03h mm-xxx-xxx VectorPath 23
LSS reg16/32/64, mem16:16/32 0Fh B2h mm-xxx-xxx VectorPath ~
LTR mreg16 0Fh 00h 11-011-xxx VectorPath ~
LTR mem16 0Fh 00h mm-011-xxx VectorPath ~
Table 13. Integer Instructions (Continued)
Syntax
Encoding
Decode
type
Latency Note
First
byte
Second
byte
ModRM
byte
Notes:
1. Static timing assumes a predicted branch.
2. Store operation also updates ESP—the new register value is available one clock earlier than the specified
latency.
3. The clock count, regardless of the number of shifts or rotates, as determined by CL or imm8.
4. LEA instructions have a latency of 1 when there are two source operands (as in the case of the base + index
form LEA EAX, [EDX+EDI]). Forms with a scale or more than two source operands will have a latency of 2 (LEA
EAX, [EBX+EBX*8]).
5. These instructions have an effective latency as shown. They map to internal NOPs that can be issued at a rate of
three per cycle but do not occupy execution resources.
6. The latency of repeated string instructions can be found in “Latency of Repeated String Instructions” on
page 167.
7. The first latency value is for 32-bit mode. The second is for 64-bit mode.
8. This opcode is used as a REX prefix in 64-bit mode.