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ddibyend (Dibyendu Das)
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User Since
Sep 23 2014, 10:14 AM (221 w, 22 h)

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Jan 5 2018

ddibyend added a comment to D41723: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715, "Branch Target Injection", and is one of the two halves to Spectre...

For AMD processors we may be able to handle indirect jumps via a simpler lfence mechanism. Indirect calls may still require retpoline. If this turns out to be the right solution for AMD processors we may need to put some code in to support this.

Jan 5 2018, 3:14 AM

Dec 7 2017

ddibyend added a comment to D40865: X86 AVX2: Prefer one VPERMV over ShuffleAsRepeatedMaskAndLanePermute.

vpermps/vpermpd/vpermd have high cost in Ryzen. I see that this patch creates cases where a vperm* is introduced where one did not exist earlier. That may cause slowdowns in Ryzen.

Dec 7 2017, 1:29 AM