Advanced Performance Extensions expand the entire x86 instruction set with access to more registers and adds various new features that improve general-purpose performance.
Intel® APX doubles the number of general-purpose registers (GPRs) from 16 to 32. This allows the compiler to keep more values in registers; as a result, APX-compiled code contains 10% fewer loads and more than 20% fewer stores than the same code compiled for an Intel® 64 baseline.2 Register accesses are not only faster, but they also consume significantly less dynamic power than complex load and store operations.
Intel® APX adds conditional forms of load, store, and compare/test instructions, and it also adds an option for the compiler to suppress the status flags writes of common instructions. These enhancements expand the applicability of if-conversion to much larger code regions, cutting down on the number of branches that may incur misprediction penalties. All these conditional ISA improvements are implemented via EVEX prefix extensions of existing legacy instructions.
The changes: