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Buffer LLVM's object output stream

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In some profiling on OSX I saw the `write` syscall as quite high up on
the profiling graph, which is definitely not good! It looks like we're
setting the output stream of an object file as directly to a file
descriptor which means that we run the risk of doing lots of little
writes rather than a few large writes.

This commit fixes this issue by adding a buffered stream on the output,
causing the `write` syscall to disappear from the profiles on OSX.
This commit is contained in:
Alex Crichton
2018-08-19 23:44:25 -07:00
parent 3ac79c7184
commit 9d54bf8df2
1 changed files with 2 additions and 1 deletions
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3
src/rustllvm/PassWrapper.cpp
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@@ -556,7 +556,8 @@ LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR,
} }
#if LLVM_VERSION_GE(7, 0) #if LLVM_VERSION_GE(7, 0)
unwrap(Target)->addPassesToEmitFile(*PM, OS, nullptr, FileType, false); buffer_ostream BOS(OS);
unwrap(Target)->addPassesToEmitFile(*PM, BOS, nullptr, FileType, false);
#else #else
unwrap(Target)->addPassesToEmitFile(*PM, OS, FileType, false); unwrap(Target)->addPassesToEmitFile(*PM, OS, FileType, false);
#endif #endif