Set PrepareForThinLTO flag when using ThinLTO #50684
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The LLVM PassManager has a PrepareForThinLTO flag, which is intended when compilation occurs in conjunction with linking by ThinLTO. The flag has two effects: * The NameAnonGlobal pass is run after all other passes, which ensures that all globals have a name. * In optimized builds, a number of late passes (mainly related to vectorization and unrolling) are disabled, on the rationale that these a) will increase codesize of the intermediate artifacts and b) will be run by ThinLTO again anyway. This patch enables the use of PrepareForThinLTO if Thin or ThinLocal linking is used. The background for this change is the CI failure in rust-lang#49479, which we assume to be caused by the NameAnonGlobal pass not being run. As this changes which passes LLVM runs, this might have performance (or other) impact, so we want to land this separately.
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@bors r+ |
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📌 Commit a70ef4c has been approved by |
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Would it be possible to also get a perf run for this? |
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Once it lands we'll get perf from that, we can run perf separately too, though. @bors try |
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Set PrepareForThinLTO flag when using ThinLTO The LLVM PassManager has a PrepareForThinLTO flag, which is intended for use when compilation occurs in conjunction with linking by ThinLTO. The flag has two effects: * The NameAnonGlobal pass is run after all other passes, which ensures that all globals have a name. * In optimized builds, a number of late passes (mainly related to vectorization and unrolling) are disabled, on the rationale that these a) will increase codesize of the intermediate artifacts and b) will be run by ThinLTO again anyway. This patch enables the use of PrepareForThinLTO if Thin or ThinLocal linking is used. The background for this change is the CI failure in #49479, which we assume to be caused by the NameAnonGlobal pass not being run. As this changes which passes LLVM runs, this might have performance (or other) impact, so we want to land this separately.
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☀️ Test successful - status-travis |
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May 12, 2018
Set PrepareForThinLTO flag when using ThinLTO The LLVM PassManager has a PrepareForThinLTO flag, which is intended for use when compilation occurs in conjunction with linking by ThinLTO. The flag has two effects: * The NameAnonGlobal pass is run after all other passes, which ensures that all globals have a name. * In optimized builds, a number of late passes (mainly related to vectorization and unrolling) are disabled, on the rationale that these a) will increase codesize of the intermediate artifacts and b) will be run by ThinLTO again anyway. This patch enables the use of PrepareForThinLTO if Thin or ThinLocal linking is used. The background for this change is the CI failure in #49479, which we assume to be caused by the NameAnonGlobal pass not being run. As this changes which passes LLVM runs, this might have performance (or other) impact, so we want to land this separately.
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☀️ Test successful - status-appveyor, status-travis |
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Looks like small improvements to non-incremental optimized builds across most crates. Hopefully no corresponding runtime regressions... |
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Those improvements are nothing to sneeze at, pretty sure the Gecko people will be happy about this. |
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The LLVM PassManager has a PrepareForThinLTO flag, which is intended for use when compilation occurs in conjunction with linking by ThinLTO. The flag has two effects:
This patch enables the use of PrepareForThinLTO if Thin or ThinLocal linking is used.
The background for this change is the CI failure in #49479, which we assume to be caused by the NameAnonGlobal pass not being run. As this changes which passes LLVM runs, this might have performance (or other) impact, so we want to land this separately.