1 files changed, 78 insertions, 2 deletions
diff --git a/llvm/lib/Support/DJB.cpp b/llvm/lib/Support/DJB.cpp
index c696f1e6a0b..b7bfbbf7bd8 100644
--- a/llvm/lib/Support/DJB.cpp
+++ b/llvm/lib/Support/DJB.cpp
@@ -12,9 +12,85 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/DJB.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/ConvertUTF.h"
+#include "llvm/Support/Unicode.h"
+
+using namespace llvm;
+
+static inline uint32_t djbHashChar(unsigned char C, uint32_t H) {
+  return (H << 5) + H + C;
+}
 
 uint32_t llvm::djbHash(StringRef Buffer, uint32_t H) {
-  for (char C : Buffer.bytes())
-    H = ((H << 5) + H) + C;
+  for (unsigned char C : Buffer.bytes())
+    H = djbHashChar(C, H);
+  return H;
+}
+
+static UTF32 chopOneUTF32(StringRef &Buffer) {
+  UTF32 C;
+  const UTF8 *const Begin8Const =
+      reinterpret_cast<const UTF8 *>(Buffer.begin());
+  const UTF8 *Begin8 = Begin8Const;
+  UTF32 *Begin32 = &C;
+
+  // In lenient mode we will always end up with a "reasonable" value in C for
+  // non-empty input.
+  assert(!Buffer.empty());
+  ConvertUTF8toUTF32(&Begin8, reinterpret_cast<const UTF8 *>(Buffer.end()),
+                     &Begin32, &C + 1, lenientConversion);
+  Buffer = Buffer.drop_front(Begin8 - Begin8Const);
+  return C;
+}
+
+static StringRef toUTF8(UTF32 C, MutableArrayRef<UTF8> Storage) {
+  const UTF32 *Begin32 = &C;
+  UTF8 *Begin8 = Storage.begin();
+
+  // The case-folded output should always be a valid unicode character, so use
+  // strict mode here.
+  ConversionResult CR = ConvertUTF32toUTF8(&Begin32, &C + 1, &Begin8,
+                                           Storage.end(), strictConversion);
+  assert(CR == conversionOK && "Case folding produced invalid char?");
+  (void)CR;
+  return StringRef(reinterpret_cast<char *>(Storage.begin()),
+                   Begin8 - Storage.begin());
+}
+
+static UTF32 foldCharDwarf(UTF32 C) {
+  // DWARF v5 addition to the unicode folding rules.
+  // Fold "Latin Small Letter Dotless I" and "Latin Capital Letter I With Dot
+  // Above" into "i".
+  if (C == 0x130 || C == 0x131)
+    return 'i';
+  return sys::unicode::foldCharSimple(C);
+}
+
+static uint32_t caseFoldingDjbHashCharSlow(StringRef &Buffer, uint32_t H) {
+  UTF32 C = chopOneUTF32(Buffer);
+
+  C = foldCharDwarf(C);
+
+  std::array<UTF8, UNI_MAX_UTF8_BYTES_PER_CODE_POINT> Storage;
+  StringRef Folded = toUTF8(C, Storage);
+  return djbHash(Folded, H);
+}
+
+uint32_t llvm::caseFoldingDjbHash(StringRef Buffer, uint32_t H) {
+  while (!Buffer.empty()) {
+    unsigned char C = Buffer.front();
+    if (LLVM_LIKELY(C <= 0x7f)) {
+      // US-ASCII, encoded as one character in utf-8.
+      // This is by far the most common case, so handle this specially.
+      if (C >= 'A' && C <= 'Z')
+        C = 'a' + (C - 'A'); // fold uppercase into lowercase
+      H = djbHashChar(C, H);
+      Buffer = Buffer.drop_front();
+      continue;
+    }
+    H = caseFoldingDjbHashCharSlow(Buffer, H);
+  }
   return H;
 }