dblaikie added a comment. In D99160#2670460 <https://reviews.llvm.org/D99160#2670460>, @djtodoro wrote:
> In D99160#2669576 <https://reviews.llvm.org/D99160#2669576>, @dblaikie wrote: > >> In D99160#2668977 <https://reviews.llvm.org/D99160#2668977>, @djtodoro wrote: >> >>> I think that the Debug Entry Values feature should not be enabled by >>> default for non optimized code, so the >>> `TargetOptions::ShouldEmitDebugEntryValues()` should be patched with >>> checking of optimization level (it should be > 0). >> >> That's currently intended to be already handled by the frontend, right? >> (clang only sets `EnableDebugEntryValues` (which >> `ShouldEmitDebugEntryValues` checks (hmm, it checks under 'or', not 'and', >> so I'm not sure where the "only above -O0" is implemented, but it is >> implemented somewhere?) if optimizations are enabled, yeah?) >> >> Oh, is entry_values actually not conditionalized? It's only the call_site >> support that's currently conditionalized on "above -O0"? > > Looks like there is no explicit check of optimization level (above "-O0"), > neither on frontend nor backend for entry-values generation. I think it is > the situation since there should not be any optimization (at least that I am > aware of, in the case of C/C++) that would cause the entry-values > generation... > >> Hmm - If that's the case, and we currently have some cases where >> entry_values are emitted at -O0, I'm not sure /not/ emitting those is the >> right call either. If we believe/have data to show that there are so few >> useful uses of entry_value at -O0 that it's not worth the DWARF size growth >> to put call_sites in at -O0, then I think it might still be worth leaving >> the entry_values in (unless they take up a bunch of extra space) for the >> cases of mixed optimization compilation (-O0 some code you're debugging, but >> building the rest with optimizations). > > Yeah... That is valuable example... I am thinking in that direction as well, > and I am closer to the enabling it for -O0 case if that is useful (and there > is no dramatic cost in terms of DWARF size). Does anyone have this example (where DW_OP_entry_value is used at -O0)? It'd be great to look at it & see if it's a case of unnecessarily losing the location, or legitimately losing it and using entry_value for best-effort recovery (& then a question of whether the loss is appropriate at -O0, or if we want to pessimize -O0 further to avoid the loss). I'd worry about turning on call_sites at -O0 - there'd be a lot more calls (especially for C++ code with lots of implicit operations), but numbers will be needed in any case, so not worth much speculation. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D99160/new/ https://reviews.llvm.org/D99160 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
