Difference in output of llvm-args=--help-list-hidden when llvm.linked-shared is set to true or false #115564
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`-Cllvm-args` usability improvement fixes: rust-lang#26338 fixes: rust-lang#115564 Two problems were found during playing with `-Cllvm-args` 1. When `llvm.link-shared` is set to `false` in `config.toml`, output of `rustc -C llvm-args='--help-list-hidden'` doesn't contain `--emit-dwarf-unwind` and `--emulated-tls`. When it is set to `true`, `rustc -C llvm-args='--help-list-hidden'` emits `--emit-dwarf-unwind`, but `--emulated-tls` is still missing. 2. Setting `-Cllvm-args=--emit-dwarf-unwind=always` doesn't take any effect, but `-Cllvm-args=-machine-outliner-reruns=3` does work. ### 1 Adding `RegisterCodeGenFlags` to register codegen flags fixed the first problem. `rustc -C llvm-args='--help-list-hidden'` emits full codegen flags including `--emit-dwarf-unwind` and `--emulated-tls`. ### 2 Constructing `TargetOptions` from `InitTargetOptionsFromCodeGenFlags` in `LLVMRustCreateTargetMachine` fixed the second problem. The `LLVMRustSetLLVMOptions` calls `ParseCommandLineOptions` which parses given `llvm-args`. For options like `machine-outliner-reruns`, it just works, since the codegen logic directly consumes the parsing result: [machine-outliner-reruns register](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/lib/CodeGen/MachineOutliner.cpp#L114) [machine-outliner-reruns consumption](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/lib/CodeGen/MachineOutliner.cpp#L1138) But for flags defined in `TargetOptions` and `MCTargetOptions` to take effect, constructing them with `InitTargetOptionsFromCodeGenFlags` is essential, or the parsing result is just not consumed. Similar patterns can be observed in [lli](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/tools/llc/llc.cpp#L494), [llc](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/tools/lli/lli.cpp#L517), etc.
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Rollup merge of rust-lang#115638 - ldm0:ldm/llvm-args-fix, r=nikic `-Cllvm-args` usability improvement fixes: rust-lang#26338 fixes: rust-lang#115564 Two problems were found during playing with `-Cllvm-args` 1. When `llvm.link-shared` is set to `false` in `config.toml`, output of `rustc -C llvm-args='--help-list-hidden'` doesn't contain `--emit-dwarf-unwind` and `--emulated-tls`. When it is set to `true`, `rustc -C llvm-args='--help-list-hidden'` emits `--emit-dwarf-unwind`, but `--emulated-tls` is still missing. 2. Setting `-Cllvm-args=--emit-dwarf-unwind=always` doesn't take any effect, but `-Cllvm-args=-machine-outliner-reruns=3` does work. ### 1 Adding `RegisterCodeGenFlags` to register codegen flags fixed the first problem. `rustc -C llvm-args='--help-list-hidden'` emits full codegen flags including `--emit-dwarf-unwind` and `--emulated-tls`. ### 2 Constructing `TargetOptions` from `InitTargetOptionsFromCodeGenFlags` in `LLVMRustCreateTargetMachine` fixed the second problem. The `LLVMRustSetLLVMOptions` calls `ParseCommandLineOptions` which parses given `llvm-args`. For options like `machine-outliner-reruns`, it just works, since the codegen logic directly consumes the parsing result: [machine-outliner-reruns register](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/lib/CodeGen/MachineOutliner.cpp#L114) [machine-outliner-reruns consumption](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/lib/CodeGen/MachineOutliner.cpp#L1138) But for flags defined in `TargetOptions` and `MCTargetOptions` to take effect, constructing them with `InitTargetOptionsFromCodeGenFlags` is essential, or the parsing result is just not consumed. Similar patterns can be observed in [lli](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/tools/llc/llc.cpp#L494), [llc](https://github.com/rust-lang/llvm-project/blob/0537f6354cffe546cbf47f6dc9c7f82e49e86cfb/llvm/tools/lli/lli.cpp#L517), etc.
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I noticed a difference in the output of the
llvm-args=--help-list-hiddenflag when thellvm.link-sharedconfiguration option is set to true or false in config.toml.Steps to reproduce on Mac:
llvm.link-shared=trueandllvm.download-ci-llvm=falsein theconfig.toml../x.py build./build/<triple>/stage1/bin/rustc -Cllvm-args=--help-list-hidden | rg emit-dwarf-uwindwill print the llvm optionExpected behavior:
The output of
llvm-args=--help-list-hiddenshould be consistent regardless of the value ofllvm.link-shared. So Theemit-dwarf-unwindoption should be present in the output regardless of thellvm.link-sharedsetting.Actual behavior:
When
llvm.link-sharedis set to false, theemit-dwarf-unwindoption is missing from the output ofllvm-args=--help-list-hidden. And llvm was statically linked within rustc on non-Linux platform, while statically linked on Linux; this difference can be seen on Linux and Mac.Rust Version: latest nightly
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