[PATCH] D133660: [Support] Add fast path for StringRef::find with needle of length 2.

[Tatsuyuki Ishi via Phabricator via llvm-commits]

ishitatsuyuki updated this revision to Diff 461077.
ishitatsuyuki added a comment.

Use a simplified implementation for clarity.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133660/new/

https://reviews.llvm.org/D133660

Files:
  llvm/lib/Support/StringRef.cpp


Index: llvm/lib/Support/StringRef.cpp
===================================================================
--- llvm/lib/Support/StringRef.cpp
+++ llvm/lib/Support/StringRef.cpp
@@ -148,6 +148,18 @@
 
   const char *Stop = Start + (Size - N + 1);
 
+  if (N == 2) {
+    // Provide a fast path for newline finding (CRLF case) in InclusionRewriter.
+    // Not the most optimized strategy, but getting memcmp inlined should be
+    // good enough.
+    do {
+      if (std::memcmp(Start, Needle, 2) == 0)
+        return Start - Data;
+      ++Start;
+    } while (Start < Stop);
+    return npos;
+  }
+
   // For short haystacks or unsupported needles fall back to the naive algorithm
   if (Size < 16 || N > 255) {
     do {


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