[ADT] Add a single-character version of the small vector split routine
on StringRef. Finding and splitting on a single character is
substantially faster than doing it on even a single character StringRef
-- we immediately get to a *very* tuned memchr call this way.
Even nicer, we get to this even in a debug build, shaving 18% off the
runtime of TripleTest.Normalization, helping PR23676 some more.
llvm-svn: 247244
diff --git a/llvm/lib/Support/StringRef.cpp b/llvm/lib/Support/StringRef.cpp
index ddece08..f2e587c 100644
--- a/llvm/lib/Support/StringRef.cpp
+++ b/llvm/lib/Support/StringRef.cpp
@@ -294,6 +294,26 @@
A.push_back(rest);
}
+void StringRef::split(SmallVectorImpl<StringRef> &A, char Separator,
+ int MaxSplit, bool KeepEmpty) const {
+ StringRef rest = *this;
+
+ // rest.data() is used to distinguish cases like "a," that splits into
+ // "a" + "" and "a" that splits into "a" + 0.
+ for (int splits = 0;
+ rest.data() != nullptr && (MaxSplit < 0 || splits < MaxSplit);
+ ++splits) {
+ std::pair<StringRef, StringRef> p = rest.split(Separator);
+
+ if (KeepEmpty || p.first.size() != 0)
+ A.push_back(p.first);
+ rest = p.second;
+ }
+ // If we have a tail left, add it.
+ if (rest.data() != nullptr && (rest.size() != 0 || KeepEmpty))
+ A.push_back(rest);
+}
+
//===----------------------------------------------------------------------===//
// Helpful Algorithms
//===----------------------------------------------------------------------===//