hoist regexes

Author: makslevental

llvm/lib/Support/StringExtras.cpp

@@ -97,10 +97,13 @@ std::string llvm::convertToSnakeFromCamelCase(StringRef input) {
   if (input.empty())
     return "";
 
+  llvm::Regex trailingCap = llvm::Regex("([A-Z]+)([A-Z][a-z])");
+  llvm::Regex leadingCap = llvm::Regex("([a-z0-9])([A-Z])");
+
   std::string snakeCase = input.str();
   for (int i = 0; i < 10; ++i) {
-    snakeCase = llvm::Regex("([A-Z]+)([A-Z][a-z])").sub("\\1_\\2", snakeCase);
-    snakeCase = llvm::Regex("([a-z0-9])([A-Z])").sub("\\1_\\2", snakeCase);
+    snakeCase = trailingCap.sub("\\1_\\2", snakeCase);
+    snakeCase = leadingCap.sub("\\1_\\2", snakeCase);
   }
   std::transform(snakeCase.begin(), snakeCase.end(), snakeCase.begin(),
                  [](unsigned char c) { return std::tolower(c); });

llvm/unittests/ADT/StringExtrasTest.cpp

@@ -185,6 +185,7 @@ TEST(StringExtrasTest, ConvertToSnakeFromCamelCase) {
   testConvertToSnakeCase("OpName", "op_name");
   testConvertToSnakeCase("opName", "op_name");
   testConvertToSnakeCase("OPName", "op_name");
+  testConvertToSnakeCase("Intel_OCL_BI", "intel_ocl_bi");
   testConvertToSnakeCase("opNAME", "op_name");
   testConvertToSnakeCase("opNAMe", "op_na_me");
   testConvertToSnakeCase("opnameE", "opname_e");