[llvm] [IR][AsmParser] Revamp how floating-point literals work in LLVM IR. (PR #121838)

[Lei Huang via llvm-commits]

lei137 wrote:

My build on Linux PPC failed with:
```
~/llvm-project/clang/lib/CodeGen/CodeGenFunction.cpp:2089:11: error: enumeration value 'SpellingNotCalculated' not handled in switch [-Werror,-Ws     witch]
 2089 |   switch (HLSLControlFlowAttr) {
           |           ^~~~~~~~~~~~~~~~~~~
1 error generated.
```

https://github.com/llvm/llvm-project/pull/121838