[llvm] [llvm] Improve implementation of StringRef::find_last_of and cie (PR #71865)

[via llvm-commits]

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@@ -268,17 +268,70 @@ StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
   return npos;
 }
 
+// See https://graphics.stanford.edu/~seander/bithacks.html#ValueInWord
+static inline uint64_t haszero(uint64_t v) {
+  return ~((((v & 0x7F7F7F7F7F7F7F7FULL) + 0x7F7F7F7F7F7F7F7FULL) | v) |
+           0x7F7F7F7F7F7F7F7FULL);
+}
+static inline uint64_t hasvalue(uint64_t x, char n) {
+  return haszero((x) ^ (~0ULL / 255 * (n)));
+}
+
+/// This is a hot spot for some clangd operations, enough to be eligible to
+/// a pseudo - vectorized implementation.
+static StringRef::size_type
+vectorized_find_last_of_specialized(const char *Data, size_t Sz, char C0,
+                                    char C1) {
+  while (Sz >= 8) {
+    Sz -= 8;
+    uint64_t Buffer = 0;
+    std::memcpy((void *)&Buffer, (void *)(Data + Sz), sizeof(Buffer));
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Ralender wrote:

Isn't there some already existing utility to do unaligned loads more explicitly ?

https://github.com/llvm/llvm-project/pull/71865