User's Manual

22007E/0—November 1999 AMD Athlon™ Processor x86 Code Optimization
Select DirectPath Over VectorPath Instructions 219
Appendix G
DirectPath versus
VectorPath Instructions
Select DirectPath Over VectorPath Instructions
Use DirectPath instructions rather than VectorPath
instructions. DirectPath instructions are optimized for decode
and execute efficiently by minimizing the number of operations
per x86 instruction, which includes ‘register←register op
memory’ as well as ‘register←register op register’ forms of
instructions.
DirectPath Instructions
The following tables contain DirectPath instructions, which
should be used in the AMD Athlon processor wherever possible:
■ Table 25, “DirectPath Integer Instructions,” on page 220
■ Table 26, “DirectPath MMX™ Instructions,” on page 227
and Table 27, “DirectPath MMX™ Extensions,” on page 228
■ Table 28, “DirectPath Floating-Point Instructions,” on
page 229
■ All 3DNow! instructions, including the 3DNow! Extensions,
are DirectPath and are listed in Table 23, “3DNow!™
Instructions,” on page 217 and Table 24, “3DNow!™ Exten-
sions,” on page 218.