tejohnson added a comment. In https://reviews.llvm.org/D42995#1000155, @vitalybuka wrote:
> In https://reviews.llvm.org/D42995#1000025, @tejohnson wrote: > > > > Empty ThinLTOIndexFile signals that we don't need this module during > > > linking. > > > > Not the only case actually. We now also pass an empty index file when we > > want to compile the bitcode down to object without applying any LTO > > optimization (there are a few cases where we decide we want to turn off LTO > > optimizations for some links), and this is currently relying on being able > > to pass /dev/null for the index file that would be broken by this change. > > > I'd expect this should be done by indexing and content is already in the > merged object file. > Not sure how to reproduce this. I've build some large targets and I never > seen this. This is done in bazel, not in gold. See below. > > >> >> >>> So we should not run ThinLTO backend even if it contains the >>> ThinLTO module. Backend may fail because of lack of necessary >>> information which should be provided by ThinLTOIndex. >> >> This shouldn't happen - are you seeing cases where we fail? After >> loadModule() is called, EmitBackendOutput() is called which passes >> /*IgnoreEmptyThinLTOIndexFile*/true to getModuleSummaryIndexForFile, which >> would cause it to return nullptr if the index file is empty. Back in >> EmitBackendOutput(), if the combined index is null we will skip ThinLTO >> compilation and fall back to normal compilation. > > I don't see for regular compilation, but I see for for CFI. Backend will not > be able to process llvm.type.test without TypeIdMap from index and it will > crash in "Instruction Select" @pcc and I already discussed this a little bit in the context of bazel. I will point you to that discussion separately. https://reviews.llvm.org/D42995 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
