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[flang-rt] Simplify INDEX with len-1 SUBSTRING. #137889

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Merged
merged 3 commits into from
Apr 30, 2025
Merged

[flang-rt] Simplify INDEX with len-1 SUBSTRING. #137889

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31e7881
[flang-rt] Simplify INDEX with len-1 SUBSTRING.
vzakhari Apr 29, 2025
95d6ee6
Use memchr.
vzakhari Apr 29, 2025
6e79166
Saved a line :)
vzakhari Apr 30, 2025
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11 changes: 11 additions & 0 deletions flang-rt/lib/runtime/character.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,17 @@ inline RT_API_ATTRS std::size_t Index(const CHAR *x, std::size_t xLen,
}
return 0;
}
if (wantLen == 1) {
// Trivial case for single character lookup.
// We can use simple forward search.
CHAR ch = want[0];
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@klausler klausler Apr 29, 2025

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This could just become a call to std::memchr() for KIND==1.

For other kinds, please add braced initialization to the two declarations here.

for (std::size_t at = 0; at < xLen; ++at) {
if (x[at] == ch) {
return at + 1;
}
}
return 0;
}
// Non-trivial forward substring search: use a simplified form of
// Boyer-Moore substring searching.
for (std::size_t at{1}; at + wantLen - 1 <= xLen;) {
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1 change: 1 addition & 0 deletions flang-rt/unittests/Runtime/CharacterTest.cpp
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Expand Up @@ -354,6 +354,7 @@ TYPED_TEST(SearchTests, IndexTests) {
{"", "a", true, 0},
{"aa", "a", false, 1},
{"aa", "a", true, 2},
{"aAA", "A", false, 2},
{"Fortran that I ran", "that I ran", false, 9},
{"Fortran that I ran", "that I ran", true, 9},
{"Fortran that you ran", "that I ran", false, 0},
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