raw_ostream: If writing a string that is larger than the buffer, write it directly instead of doing many buffer-sized writes.
This caps the number of write(2) calls per string to a maximum of 2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127010 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index 80ea740..b8839e2 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -265,15 +265,19 @@
return write(Ptr, Size);
}
- // Write out the data in buffer-sized blocks until the remainder
- // fits within the buffer.
- do {
- size_t NumBytes = OutBufEnd - OutBufCur;
- copy_to_buffer(Ptr, NumBytes);
- flush_nonempty();
- Ptr += NumBytes;
- Size -= NumBytes;
- } while (OutBufCur+Size > OutBufEnd);
+ // If the buffer is empty at this point we have a string that is larger
+ // than the buffer. It's better to write it unbuffered in this case.
+ if (BUILTIN_EXPECT(OutBufCur == OutBufStart, false)) {
+ write_impl(Ptr, Size);
+ return *this;
+ }
+
+ // We don't have enough space in the buffer to fit the string in. Insert as
+ // much as possible, flush and start over with the remainder.
+ size_t NumBytes = OutBufEnd - OutBufCur;
+ copy_to_buffer(Ptr, NumBytes);
+ flush_nonempty();
+ return write(Ptr + NumBytes, Size - NumBytes);
}
copy_to_buffer(Ptr, Size);