aaron.ballman added reviewers: rjmccall, efriedma. aaron.ballman added subscribers: efriedma, rjmccall. aaron.ballman added a comment.
In D150221#4338500 <https://reviews.llvm.org/D150221#4338500>, @qianzhen wrote: > This is useful in keeping the static variables in a patchable function > (https://clang.llvm.org/docs/AttributeReference.html#patchable-function-entry), > so that they can be directly addressed by a hot patch when the optimization > to merge them is enabled > (https://llvm.org/docs/doxygen/GlobalMerge_8cpp_source.html). I would expect that the user could write `__attribute__((used))` themselves in that case rather than use the heavy hammer of keeping all statics in the TU, right? In D150221#4332280 <https://reviews.llvm.org/D150221#4332280>, @hubert.reinterpretcast wrote: > In D150221#4332142 <https://reviews.llvm.org/D150221#4332142>, @erichkeane > wrote: > >>> This is intended to prevent "excessive transformation" to enable migration >>> of existing applications (using a non-Clang compiler) where users further >>> manipulate the object or assembly after compilation. >> >> I don't get what you mean by this? I don't currently see motivation for >> this? > > The intent is to apply the `__attribute__((__used__))` semantic to static > variables (since the front-end is likely to discard them). Additional reasons > for using `__attribute__((__used__))` applies: The compiler cannot optimize > with the assumption that it sees all direct accesses to the variable. The part I'm having a hard time understanding is why this should be a TU-level option when the user can write `__attribute__((used))` on any static that matters to them that is being dropped? This feels like a heavy hammer. Adding @rjmccall and @efriedma as codegen code owners. ================ Comment at: clang/lib/CodeGen/CodeGenModule.cpp:2201-2210 + if ((CodeGenOpts.KeepStaticConsts || CodeGenOpts.KeepStaticVariables) && D && + isa<VarDecl>(D)) { const auto *VD = cast<VarDecl>(D); - if (VD->getType().isConstQualified() && - VD->getStorageDuration() == SD_Static) - addUsedOrCompilerUsedGlobal(GV); + if (VD->getStorageDuration() == SD_Static) { + if (CodeGenOpts.KeepStaticVariables) + addUsedOrCompilerUsedGlobal(GV); + else if (CodeGenOpts.KeepStaticConsts && VD->getType().isConstQualified()) ---------------- Reformatted with whatever clang-format does for that, as I doubt I have the formatting correct. ================ Comment at: clang/lib/CodeGen/CodeGenModule.cpp:3096 + return true; + else if (CodeGenOpts.KeepStaticConsts && VD->getType().isConstQualified()) + return true; ---------------- cebowleratibm wrote: > Fold to a single return. Yup, similar suggestion here as above. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D150221/new/ https://reviews.llvm.org/D150221 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
