lebedev.ri added a comment. In D57915#1389722 <https://reviews.llvm.org/D57915#1389722>, @TomTan wrote:
> In D57915#1389560 <https://reviews.llvm.org/D57915#1389560>, @lebedev.ri > wrote: > > > In D57915#1389549 <https://reviews.llvm.org/D57915#1389549>, @TomTan wrote: > > > > > Added the tests back. Clang IR should not lower these to bswap calls > > > because they are global library functions. It might be slower to make the > > > call to library function than bswap, but this is the same for other > > > architectures supported by Windows. And just redefine global library > > > function triggers link error in some scenarios. > > > > > > I think there is some deeper reasoning is being omitted here. > > //Why// does the fact that those are "global library functions" bans clang > > from lowering them into IR? > > (and thus, "prevents" LLVM form doing optimizations) > > > The current issue could be caused by the implementation of comdat selection > in LLD as below which provides more strict conflict check than MSVC link does. > > These `_bytewap_*` in `intrin.h` were not intended as optimization, instead, > it is expected to be consistent with declarations in `stdlib.h`. For > optimization, it makes sense to enable it for all architectures supported by > Windows, and make sure it works with LLD. > > https://github.com/llvm-mirror/lld/blob/b6584c3fab115aa46dad27681af7eb3d4e5d2b35/COFF/InputFiles.cpp#L494 These functions are also listed in https://github.com/llvm-mirror/clang/blob/c18e7e9007970a3105617f03bc9d1de89fa1a3e1/include/clang/Basic/Builtins.def#L773-L775 Are you sure they shouldn't be simply dropped from `lib/Headers/intrin.h`? I notice they were just added in D56685 <https://reviews.llvm.org/D56685>, but that review has no commit message, so the problem it addressed is not documented.. So as-is this all looks a bit like hand-waving //to me//. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D57915/new/ https://reviews.llvm.org/D57915 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
