[llvm] [KnownFPClass] Refactor NaN sign encoding for KnownFPClass (PR #220606)

[Eric Ross via llvm-commits]

================
@@ -24,41 +24,219 @@ class APInt;
 struct fltSemantics;
 struct KnownBits;
 
+enum FPClassMask : unsigned {
+  kfcNone = 0,
+
+  kfcNegQNan = 0x0001,
+  kfcNegSNan = 0x0002,
+  kfcNegInf = 0x0004,
+  kfcNegNormal = 0x0008,
+  kfcNegSubnormal = 0x0010,
+  kfcNegZero = 0x0020,
+  kfcPosZero = 0x0040,
+  kfcPosSubnormal = 0x0080,
+  kfcPosNormal = 0x0100,
+  kfcPosInf = 0x0200,
+  kfcPosSNan = 0x0400,
+  kfcPosQNan = 0x0800,
+
+  kfcSNan = kfcPosSNan | kfcNegSNan,
+  kfcQNan = kfcPosQNan | kfcNegQNan,
+  kfcPosNan = kfcPosSNan | kfcPosQNan,
+  kfcNegNan = kfcNegSNan | kfcNegQNan,
+  kfcNan = kfcSNan | kfcQNan,
+  kfcInf = kfcPosInf | kfcNegInf,
+  kfcNormal = kfcPosNormal | kfcNegNormal,
+  kfcSubnormal = kfcPosSubnormal | kfcNegSubnormal,
+  kfcZero = kfcPosZero | kfcNegZero,
+  kfcPosFinite = kfcPosNormal | kfcPosSubnormal | kfcPosZero,
+  kfcNegFinite = kfcNegNormal | kfcNegSubnormal | kfcNegZero,
+  kfcFinite = kfcPosFinite | kfcNegFinite,
+  kfcPositive = kfcPosFinite | kfcPosInf,
+  kfcNegative = kfcNegFinite | kfcNegInf,
+  kfcPosSignBit = kfcPositive | kfcPosNan,
+  kfcNegSignBit = kfcNegative | kfcNegNan,
+
+  kfcAllFlags = kfcNan | kfcInf | kfcFinite,
+};
+
+LLVM_DECLARE_ENUM_AS_BITMASK(FPClassMask, /* LargestValue */ kfcPosQNan);
----------------
ZERICO2005 wrote:

`LLVM_MARK_AS_BITMASK_ENUM` does not work for `enum FPClassTest : unsigned {}`:
```c++
In file included from /home/zerico/programming/llvm-project/llvm/include/llvm/Support/BinaryStreamRef.h:13:
/home/zerico/programming/llvm-project/llvm/include/llvm/Support/BinaryStream.h:24:3: error: redefinition of enumerator 'LLVM_BITMASK_LARGEST_ENUMERATOR'
   24 |   LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append)
      |   ^
/home/zerico/programming/llvm-project/llvm/include/llvm/ADT/BitmaskEnum.h:43:3: note: expanded from macro 'LLVM_MARK_AS_BITMASK_ENUM'
   43 |   LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue
      |   ^
/home/zerico/programming/llvm-project/llvm/include/llvm/Support/KnownFPClass.h:62:3: note: previous definition is here
   62 |   LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue=*/kfcPosQNan)
      |   ^
/home/zerico/programming/llvm-project/llvm/include/llvm/ADT/BitmaskEnum.h:43:3: note: expanded from macro 'LLVM_MARK_AS_BITMASK_ENUM'
   43 |   LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue
      |   ^
1 error generated.
[383/579] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/TargetLowering.cpp.o^C
ninja: build stopped: interrupted by user.
```

https://github.com/llvm/llvm-project/pull/220606