1 files changed, 9 insertions, 8 deletions

diff --git a/contrib/llvm-project/llvm/lib/Support/StringExtras.cpp b/contrib/llvm-project/llvm/lib/Support/StringExtras.cpp
index 5683d7005584..6ae26267337b 100644
--- a/contrib/llvm-project/llvm/lib/Support/StringExtras.cpp
+++ b/contrib/llvm-project/llvm/lib/Support/StringExtras.cpp
@@ -98,15 +98,16 @@ std::string llvm::convertToSnakeFromCamelCase(StringRef input) {
 
   std::string snakeCase;
   snakeCase.reserve(input.size());
-  for (char c : input) {
-    if (!std::isupper(c)) {
-      snakeCase.push_back(c);
-      continue;
-    }
-
-    if (!snakeCase.empty() && snakeCase.back() != '_')
+  auto check = [&input](size_t j, function_ref<bool(int)> predicate) {
+    return j < input.size() && predicate(input[j]);
+  };
+  for (size_t i = 0; i < input.size(); ++i) {
+    snakeCase.push_back(tolower(input[i]));
+    // Handles "runs" of capitals, such as in OPName -> op_name.
+    if (check(i, isupper) && check(i + 1, isupper) && check(i + 2, islower))
+      snakeCase.push_back('_');
+    if ((check(i, islower) || check(i, isdigit)) && check(i + 1, isupper))
       snakeCase.push_back('_');
-    snakeCase.push_back(llvm::toLower(c));
   }
   return snakeCase;
 }