From 9d54bf8df2677dd5f985838c5686efaa24a73b6c Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Sun, 19 Aug 2018 23:44:25 -0700 Subject: [PATCH] Buffer LLVM's object output stream 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. --- src/rustllvm/PassWrapper.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/rustllvm/PassWrapper.cpp b/src/rustllvm/PassWrapper.cpp index d9fbd494ab3..46825efeee2 100644 --- a/src/rustllvm/PassWrapper.cpp +++ b/src/rustllvm/PassWrapper.cpp @@ -556,7 +556,8 @@ LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR, } #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 unwrap(Target)->addPassesToEmitFile(*PM, OS, FileType, false); #endif