[clang] [llvm] [LoongArch] [CodeGen] Add options for Clang to generate LoongArch-specific frecipe & frsqrte instructions (PR #109917)

[via cfe-commits]

================
@@ -141,6 +141,22 @@ enum NodeType : unsigned {
   VALL_NONZERO,
   VANY_NONZERO,
 
+  // Floating point approximate reciprocal operation
+  FRECIPE_S,
----------------
tangaac wrote:

We can't.
Each target-dependent ISD corresponds to a specific instruction in the backend.
Other instructions such as IOCSRRD,  IOCSRWR  have 4 different types of ISD: 
```c++
  IOCSRRD_B,
  IOCSRRD_W,
  IOCSRRD_H,
  IOCSRRD_D,
  IOCSRWR_B,
  IOCSRWR_H,
  IOCSRWR_W,
  IOCSRWR_D,
```


https://github.com/llvm/llvm-project/pull/109917