[clang] [llvm] [Clang][LoongArch] Support target attribute for function (PR #140700)

[via cfe-commits]

================
@@ -388,6 +388,51 @@ bool LoongArchTargetInfo::handleTargetFeatures(
   return true;
 }
 
+ParsedTargetAttr
+LoongArchTargetInfo::parseTargetAttr(StringRef Features) const {
+  ParsedTargetAttr Ret;
+  if (Features == "default")
+    return Ret;
+  SmallVector<StringRef, 1> AttrFeatures;
+  Features.split(AttrFeatures, ",");
+
+  for (auto &Feature : AttrFeatures) {
+    Feature = Feature.trim();
+
+    if (Feature.starts_with("arch=")) {
----------------
tangaac wrote:

I believe that the previous approach was essentially off-the-cuff, done whichever way was most convenient.

If someone were to implement the same functionality for other architectures as well, they would find three pieces of code with very poor style.

To leave behind code that is more ergonomic for future developers, at the very least, the logic for handling features should be separated and handled individually.

```c++
auto handleArch = [&](StringRef Feature) { ... }
auto handleTune = [&](StringRef Feature) { ... }

if(feature.startwith("arch=") handleArch(feature)
else (feature.startwith("tune=") handleTune(feature)
else if ( ... ) ...
else {

}

```



https://github.com/llvm/llvm-project/pull/140700