Author: Tony Werten
Date: 01:38:33 11/27/02
Nice processor :))) Quoth the Pentium 4 Optimization Manual-- Use of the inc and dec Instructions The inc and dec instructions modify only a subset of the bits in the flag register. This creates a dependence on all previous writes of the flag register. This is especially problematic when these instructions are on the critical path because they are used to change an address for a load on which many other instructions depend. Assembly/Compiler Coding Rule 41. (M impact, H generality) inc and dec instructions should be replaced with an add or sub instruction, because add and sub overwrite all flags. The optimization of implementing Coding Rule 41 benefits Pentium 4 and future IA-32 processors based on the Intel NetBurst micro-architecture, although it does not help Pentium II processors, and it adds an additional byte per instruction.
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