[FormattedStream] Add ASCII fast path #117892
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Printing IR spends a large amount of time updating the column count via generic UTF-8 APIs. Speed it up by adding a fast path for the common printable ASCII case. This makes `-print-on-crash -print-module-scope` about two times faster.
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@llvm/pr-subscribers-llvm-support Author: Nikita Popov (nikic) ChangesPrinting IR spends a large amount of time updating the column count via generic UTF-8 APIs. Speed it up by adding a fast path for the common printable ASCII case. This makes Full diff: https://github.com/llvm/llvm-project/pull/117892.diff 1 Files Affected:
diff --git a/llvm/lib/Support/FormattedStream.cpp b/llvm/lib/Support/FormattedStream.cpp
index c50530e76efc0a..4192893b38a763 100644
--- a/llvm/lib/Support/FormattedStream.cpp
+++ b/llvm/lib/Support/FormattedStream.cpp
@@ -75,6 +75,13 @@ void formatted_raw_ostream::UpdatePosition(const char *Ptr, size_t Size) {
// Now scan the rest of the buffer.
unsigned NumBytes;
for (const char *End = Ptr + Size; Ptr < End; Ptr += NumBytes) {
+ // Fast path for printable ASCII characters without special handling.
+ if (*Ptr >= 0x20 && *Ptr <= 0x7e) {
+ NumBytes = 1;
+ ++Column;
+ continue;
+ }
+
NumBytes = getNumBytesForUTF8(*Ptr);
// The buffer might end part way through a UTF-8 code unit sequence for a
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Printing IR spends a large amount of time updating the column count via generic UTF-8 APIs. Speed it up by adding a fast path for the common printable ASCII case.
This makes
-print-on-crash -print-module-scopeabout two times faster.