[PATCH] D70874: [X86] Add initialization of MXCSR in llvm-exegesis

[Pengfei Wang via Phabricator via llvm-commits]

pengfei added a comment.

> We make sure that every register that is used by an instruction in the snippet is initialized. This is to avoid having fluctuations in measurements due to performance depending on values in registers. I think it's great if SSE/AVX instructions start explicitly state their deps on MXCSR, because the behaviour does indeed depend on the value of these flags.

Thanks for the explanation. Please note that currently we only state the rounding modes and the IEEE masks bits of MXCSR. This means instructions like VRSQRT14PS, which only have dependence on FTZ and DAZ, wouldn't be modeled.


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  https://reviews.llvm.org/D70874/new/

https://reviews.llvm.org/D70874