)]}'
{
  "commit": "3e05ab6322cbf2a96362dcacb5907ba519fe552d",
  "tree": "1f85d2e4b011ff5cde05bddf65c2a002c1ea22f1",
  "parents": [
    "e317f424557cbf76deaa568ab8a5416822453d50"
  ],
  "author": {
    "name": "yonghong-song",
    "email": "yhs@fb.com",
    "time": "Sat Feb 28 12:44:25 2026 -0800"
  },
  "committer": {
    "name": "GitHub",
    "email": "noreply@github.com",
    "time": "Sat Feb 28 12:44:25 2026 -0800"
  },
  "message": "[ThinLTO] Reduce the number of renaming due to promotions (#183793)\n\nCurrently for thin-lto, the imported static global values (functions,\nvariables, etc) will be promoted/renamed from e.g., foo() to\nfoo.llvm.(). Such a renaming caused difficulties in live patching\nsince function name is changed ([1]).\n\nIt is possible that some global value names have to be promoted to avoid\nname collision and linker failure. But in practice, majority of name\npromotions can be avoided.\n\nIn [2], the suggestion is that thin-lto pre-link decides whether\na particular global value needs name promotion or not. If yes, later on\nin thinBackend() the name will be promoted.\n\nI compiled a particular linux kernel version (latest bpf-next tree)\nand found 1216 global values with suffix .llvm.. With this patch,\nthe number of promoted functions is 2, 98% reduction from the\noriginal kernel build.\n\nIf some native objects are not participating with LTO, name promotions\nhave to be done to avoid potential linker issues. So the current\nimplementation cannot be on by default. But in certain cases, e.g., linux kernel\nbuild, people can enable lld flag --lto-whole-program-visibility to reduce the\nnumber of functions like foo.llvm.().\n\nFor ThinLTOCodeGenerator.cpp which is used by llvm-lto tool and a\nfew other rare cases, reducing the number of renaming due to promotion,\nis not implemented as lld flag \u0027-lto-whole-program-visibility\u0027 is not\nsupported in ThinLTOCodeGenerator.cpp for now. In summary, this pull\nrequest only supports llvm-lto2 style workflow.\n\nThe feature is off by default. To enable the future, lld flag\n\u0027-lto-whole-program-visibility\u0027  and llvm flag\n\u0027-always-rename-promoted-locals\u003dfalse\u0027 are needed.\n\nThe link [3] has more context for the pull request discussions.\n\n[1] https://lpc.events/event/19/contributions/2212\n[2] https://discourse.llvm.org/t/rfc-avoid-functions-like-foo-llvm-for-kernel-live-patch/89400\n[3] https://github.com/llvm/llvm-project/pull/178587",
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