kimgr added a comment. In https://reviews.llvm.org/D43578#1067974, @rsmith wrote:
> In https://reviews.llvm.org/D43578#1067891, @kimgr wrote: > > > I disagreed up until the last paragraph :) > > > Can you say which things you disagree with? There seem to be two important > facts here: > > 1. LLVM's timing infrastructure cannot correctly report timings when one > function containing a timing region calls another. That will happen all the > time with this patch applied. > 2. Clang's architecture means that if you time the amount of time spent in, > say, the "ParseTemplate" function, you have not computed the amount of time > spent parsing templates, because the parser calls into Sema, which might > perform tasks that are only somewhat related to parsing the template (such as > performing other instantiations), and likewise Sema calls into other layers > (such as AST file deserialization and code generation). > > The first might have been fixed in LLVM at this point, but I can't see any > evidence of that in LLVM's Timer implementation. And the second seems even > more fundamental. But if there's some way around that, which would allow us > to produce (correct!) numbers for times spent parsing / whatever else, > without, for instance, adding a correctness requirement that we annotate > every Parser -> Sema entry point with a timer, then that's definitely > something we should discuss. Ah, I see. I read your original message as dismissive as in users don't need to know where time is spent. I tried to make the case that users do care where time is spent, because it can give a hint as to what part of their physical/logical design they can work on to get better compile times. But I think you were really saying that LLVM and Clang as designed can't provide anything perfect, only slightly misleading information? Sorry for the misunderstanding. - Kim https://reviews.llvm.org/D43578 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
