AMD AMD5K86 - Performance; Code Optimization; General Superscalar Techniques

18524BjO-Marl996
AMD~
AMD5~6 Processor Technical Reference Manual
4
Performance
This chapter provides information to assist fast execution and
details on dispatch and execution timing for x86 instructions.
Throughout the chapter, the terms clock and cycle refer to pro-
cessor clock cycles, not bus clock (eLK) cycles.
4.1 Code Optimization
The code optimization suggestions in this section cover both
general super scalar optimization (that is, techniques common
to both the AMD5
K
86 and Pentium processors) and techniques
specific to the AMD5
K
86 processor. In general, all optimization
techniques used for the Pentium processor apply to any wide-
issue x86 processor, but wider-issue designs like the AMD5
K
86
processor have fewer restrictions.
4.1.1 General Superscalar Techniques
Code Optimization
• Short Forms-Use shorter forms of instructions to increase
the effective number of instructions that can be examined
for decoding at anyone time. Use 8-bit displacements and
jump offsets where possible.
• Simple Instructions-Use simple instructions with hard-
wired decode because they often perform more efficiently.
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