[llvm] [llvm][Support] fix convertToSnakeFromCamelCase (PR #68375)

[via llvm-commits]

llvmbot wrote:


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@llvm/pr-subscribers-llvm-adt

<details>
<summary>Changes</summary>

Currently runs of caps aren't handled correctly so e.g. something like `Intel_OCL_BI` is snake cased to `intel_o_c_l_b_i` (previously discussed on this [phabricator patch](https://reviews.llvm.org/rG92233062c17590d3157bdc6db430fcdfc54312fe)). The easiest way to fix was to use regexes instead of the existing loop. Full disclosure the regexes were pulled from [inflection](https://github.com/jpvanhal/inflection/blob/88eefaacf7d0caaa701af7c8ab2d0ab3f17086f1/inflection/__init__.py#L416-L418) but it should be pretty clear they're correct.


---
Full diff: https://github.com/llvm/llvm-project/pull/68375.diff


2 Files Affected:

- (modified) llvm/lib/Support/StringExtras.cpp (+7-11) 
- (modified) llvm/unittests/ADT/StringExtrasTest.cpp (+5) 


``````````diff
diff --git a/llvm/lib/Support/StringExtras.cpp b/llvm/lib/Support/StringExtras.cpp
index 5683d7005584eb2..fd5a34fb3d6e82c 100644
--- a/llvm/lib/Support/StringExtras.cpp
+++ b/llvm/lib/Support/StringExtras.cpp
@@ -12,6 +12,7 @@
 
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Regex.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cctype>
 
@@ -96,18 +97,13 @@ std::string llvm::convertToSnakeFromCamelCase(StringRef input) {
   if (input.empty())
     return "";
 
-  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() != '_')
-      snakeCase.push_back('_');
-    snakeCase.push_back(llvm::toLower(c));
+  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);
   }
+  std::transform(snakeCase.begin(), snakeCase.end(), snakeCase.begin(),
+                 [](unsigned char c) { return std::tolower(c); });
   return snakeCase;
 }
 
diff --git a/llvm/unittests/ADT/StringExtrasTest.cpp b/llvm/unittests/ADT/StringExtrasTest.cpp
index 3f69c91b270a355..fab562f1ed0d594 100644
--- a/llvm/unittests/ADT/StringExtrasTest.cpp
+++ b/llvm/unittests/ADT/StringExtrasTest.cpp
@@ -184,6 +184,11 @@ TEST(StringExtrasTest, ConvertToSnakeFromCamelCase) {
 
   testConvertToSnakeCase("OpName", "op_name");
   testConvertToSnakeCase("opName", "op_name");
+  testConvertToSnakeCase("OPName", "op_name");
+  testConvertToSnakeCase("opNAME", "op_name");
+  testConvertToSnakeCase("opNAMe", "op_na_me");
+  testConvertToSnakeCase("opnameE", "opname_e");
+  testConvertToSnakeCase("OPNameOPName", "op_name_op_name");
   testConvertToSnakeCase("_OpName", "_op_name");
   testConvertToSnakeCase("Op_Name", "op_name");
   testConvertToSnakeCase("", "");

``````````

</details>


https://github.com/llvm/llvm-project/pull/68375