rnk added a comment. In https://reviews.llvm.org/D47672#1122013, @ethanhs wrote:
> In https://reviews.llvm.org/D47672#1121181, @rnk wrote: > > > > > > > > > They are a hint to the processor that this is a short critical section, and > > it is likely that the entire critical section can be entered, run, and > > committed to memory before another thread needs to use the memory used by > > the critical section. Your implementation doesn't add these prefixes, but > > the code will execute correctly. This functionality relies on TSX, which it > > looks like Intel added some time in 2014, so it's probably widely available. > > > > Personally, I don't want to implement these intrinsics this way. We've > > already implemented intrinsics "our way" instead of doing whatever Visual C > > does, and it just leads to developer confusion when they discover that the > > compiler didn't emit the instruction they want. For example, the rotate > > intrinsics often don't work (https://llvm.org/pr37387) and the > > bittestandset (bts) intrinsics are just broken (http://llvm.org/pr33188). > > I see. AIUI, the HLE versions just add optional hints, so there should not be > any functional differences beyond using the hints or not (theses are > optimization hints, yes?). Perhaps I misunderstood the documentation. Yes, as far as I can tell. >> are there any plans for representing HLE hints on atomic instructions in >> LLVM IR? > > This would be quite nice to have, the main reason I implemented these > functions this way is I don't have the bandwidth at the moment to correctly > implement HLE in LLVM/Clang, nor some of the requisite knowledge I'm sure. I > also am keen to have Python build with clang-cl on Windows :) But I > definitely can understand wanting to do things correctly from the start. Yeah, I was kind of hoping an HLE expert would appear and suggest a straightforward implementation path. > I am going to the LLVM Bay Area monthly social Thursday so if someone wants > to discuss this there I'd be more than happy to. I should also be able to make it this week, hope to see you there! Repository: rC Clang https://reviews.llvm.org/D47672 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
