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1768898680
Adds an LTO option to indicate that whether we are linking with an allocator that supports hot/cold operator new interfaces. If not, at the start of the LTO backends any existing memprof hot/cold attributes are removed from the IR, and we also remove memprof metadata so that post-LTO inlining doesn't add any new attributes. This is done via setting a new flag in the module summary index. It is important to communicate via the index to the LTO backends so that distributed ThinLTO handles this correctly, as they are invoked by separate clang processes and the combined index is how we communicate information from the LTO link. Specifically, for distributed ThinLTO the LTO related processes look like: ``` # Thin link: $ lld --thinlto-index-only obj1.o ... objN.o -llib ... # ThinLTO backends: $ clang -x ir obj1.o -fthinlto-index=obj1.o.thinlto.bc -c -O2 ... $ clang -x ir objN.o -fthinlto-index=objN.o.thinlto.bc -c -O2 ``` It is during the thin link (lld --thinlto-index-only) that we have visibility into linker dependences and want to be able to pass the new option via -Wl,-supports-hot-cold-new. This will be recorded in the summary indexes created for the distributed backend processes (*.thinlto.bc) and queried from there, so that we don't need to know during those individual clang backends what allocation library was linked. Since in-process ThinLTO and regular LTO also use a combined index, for consistency we query the flag out of the index in all LTO backends. Additionally, when the LTO option is disabled, exit early from the MemProfContextDisambiguation handling performed during LTO, as this is unnecessary. Depends on D149117 and D149192. Differential Revision: https://reviews.llvm.org/D149215