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tehjh's profile
Jann Horn
Jann Horn
Jann Horn
@tehjh

Tweets

Jann Horn

@tehjh

works at Google Project Zero. personal account.

Joined August 2011

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    1. Chandler Carruth‏ @chandlerc1024 May 14
      • Report Tweet
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      Chandler Carruth Retweeted Chandler Carruth

      I would like to thank all my Twitter followers for ensuring in this thread that, indeed, I *did* in fact die on this hill, repeatedly and pointlessly.https://twitter.com/chandlerc1024/status/1261006073789480960 …

      Chandler Carruth added,

      Chandler Carruth @chandlerc1024
      "performant" isn't a word and even if it were has no meaning. Everyone needs to stop using it. Performance *at what*? What level is being targeted? If it's just an improvement, say that.... Anyways, I think this qualifies as a petty and silly hill, but I'm totally on it. https://twitter.com/ChuckWendig/status/1260011617644802051 …
      7 replies 2 retweets 79 likes
    2. Jon Masters  🏴‍☠️‏ @jonmasters May 14
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      Replying to @chandlerc1024

      Mental note made to use that word next chance I get to hang our with ya 😉

      1 reply 0 retweets 1 like
    3. Matt Miller‏ @epakskape May 14
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      Replying to @jonmasters @chandlerc1024

      Uh oh... Looks like I used this word in an upcoming presentation that I already recorded 😬pic.twitter.com/j09BQxPwBi

      1 reply 0 retweets 1 like
    4. Chandler Carruth‏ @chandlerc1024 May 15
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      Replying to @epakskape @jonmasters

      I will find some way to reap retribution on you both.... Ok, now time to design a compiler that introduces *more* speculative execution vulnerabilities into code, and somehow hoodwink MS into using it.....

      1 reply 0 retweets 3 likes
    5. Jann Horn‏ @tehjh May 15
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      Replying to @chandlerc1024 @epakskape @jonmasters

      I'm sure you can come up with a compiler pass that makes indirect branches more performant by adding a branch and direct call for the most likely callee. (And sneak in some new spectre-v1 type confusions that way.)

      1 reply 0 retweets 4 likes
      Jann Horn‏ @tehjh May 15
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      Replying to @tehjh @chandlerc1024 and

      if you place the branch the right way around, you can probably even make the type confusion happen on BTB miss, so no messy training will be necessary

      1:42 AM - 15 May 2020
      • 3 Likes
      • Daniel Gruss Matt Denton Chandler Carruth
      1 reply 0 retweets 3 likes
        1. Jann Horn‏ @tehjh May 15
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          Replying to @tehjh @chandlerc1024 and

          Measure performance in a microbenchmark carefully crafted such that the branch predictor state is gone on every call and the function pointer is evicted from at least L1D.

          0 replies 0 retweets 4 likes
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