3 ms·
If the PREFETCH_EX flag was never passed, why did the branch predictor speculatively execute xdcbt? That branch would never be taken, so it ought not to be pred
by ridiculous_fish 5y ago
If the PREFETCH_EX flag was never passed, why did the branch predictor speculatively execute xdcbt? That branch would never be taken, so it ought not to be predicted.
Was it a static branch prediction hint? I know PowerPC has that. If so, could it have fixed by just flipping the hint bit?
- userbinator 5y agoFrom the article: Instead simple branch predictors typically squish together a bunch of address bits, maybe some branch history bits as well, and index into an array of two-bit entries. Thus, the branch predict result is affected by other, unrelated branches, leading to sometimes spurious predictions.
- ridiculous_fish 5y agoAhh thanks, shame on me for not reading to the end.
- saagarjha 5y agoShould’ve let the full thing execute before speculating on the results ;)