Commit 9f6b13e5 authored by Johannes Doerfert's avatar Johannes Doerfert
Browse files

[Support] Fix behavior of StringRef::count with overlapping occurrences, add tests 

Summary:
Fix the behavior of StringRef::count(StringRef) to not count overlapping occurrences, as is stated in the documentation.
Fixes bug https://bugs.llvm.org/show_bug.cgi?id=44072

I added Krzysztof Parzyszek to review this change because a use of this function in HexagonInstrInfo::getInlineAsmLength might depend on the overlapping-behavior. I don't have enough domain knowledge to tell if this change could break anything there.

All other uses of this method in LLVM (besides the unit tests) only use single-character search strings. In those cases, search occurrences can not overlap anyway.

Patch by Benno (@Bensge)

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D70585
parent a36ddf0a

llvm/lib/Support/StringRef.cpp

+7 −2
Original line number Diff line number Diff line
@@ -374,9 +374,14 @@ size_t StringRef::count(StringRef Str) const { 
  size_t N = Str.size();

  if (N > Length)

    return 0;

  for (size_t i = 0, e = Length - N + 1; i != e; ++i)

    if (substr(i, N).equals(Str))

  for (size_t i = 0, e = Length - N + 1; i < e;) {

    if (substr(i, N).equals(Str)) {

      ++Count;

      i += N;

    }

    else

      ++i;

  }

  return Count;

}

llvm/unittests/ADT/StringRefTest.cpp

+7 −0
Original line number Diff line number Diff line
@@ -509,6 +509,13 @@ TEST(StringRefTest, Count) { 
  EXPECT_EQ(1U, Str.count("hello"));

  EXPECT_EQ(1U, Str.count("ello"));

  EXPECT_EQ(0U, Str.count("zz"));



  StringRef OverlappingAbba("abbabba");

  EXPECT_EQ(1U, OverlappingAbba.count("abba"));

  StringRef NonOverlappingAbba("abbaabba");

  EXPECT_EQ(2U, NonOverlappingAbba.count("abba"));

  StringRef ComplexAbba("abbabbaxyzabbaxyz");

  EXPECT_EQ(2U, ComplexAbba.count("abba"));

}



TEST(StringRefTest, EditDistance) {