Справочник Пользователя для AMD 250
Chapter 9
Optimizing with SIMD Instructions
209
Software Optimization Guide for AMD64 Processors
25112
Rev. 3.06
September 2005
9.9
Storing Floating-Point Data in MMX™ Registers
Optimization
Avoid storing floating-point data in MMX registers unless using 3DNow! instructions.
Application
This optimization applies to:
•
32-bit software
•
64-bit software
Rationale
Using MOVDQ2Q or MOVQ2DQ to shuffle integer data between MMX and XMM registers is useful
to relieve register pressure; however, doing so with floating-point data can impact performance. The
impact is greater if the floating-point data is denormalized.
to relieve register pressure; however, doing so with floating-point data can impact performance. The
impact is greater if the floating-point data is denormalized.