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Hardware Lock Elision on Haswell
- userbinator 13y agoInteresting to see that they're reusing what used to be the REP/REPNZ prefices for this purpose, rather than assigning a completely new (and likely 0F+) opcode. I suppose it's because the existing instruction decoder already recognises it as a prefix (they would just be ignored pre-Haswell.)
- mjb 13y agoExactly. As I understand it, HLE programs that use XACQUIRE and XRELEASE should run fine on older hardware. I suspect Intel's play here is to get the technology into mainstream compilers and libraries quickly, to make their Haswell and newer processors look good on benchmarks without special compiler flags.
- baq 13y agoyou make it sound like being able to ship one binary that's backwards compatible with previous processors was a bad thing.
- mjb 13y agoNot a bad thing, just a compromise. It does restrict the feature set of HLE a little bit, and make some of its semantics a little awkward. Backward compatibility is obviously a good and useful thing. I think Intel did the right thing for their business and their customers, but probably not the right thing for the long-term prettiness of the assembly.