[CIR] Add some IITDescriptor types

This patch adds support for the following IITDescriptor types and adds
NYI for the others.

```cpp
IITDescriptor::Half
IITDescriptor::BFloat
IITDescriptor::Vector
```

Author: anirudhsundar

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

@@ -19,6 +19,7 @@
 #include "CIRGenValue.h"
 #include "TargetInfo.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/Type.h"
 #include "clang/CIR/Dialect/IR/CIRAttrs.h"
 #include "clang/CIR/Dialect/IR/CIROpsEnums.h"
 #include "clang/CIR/MissingFeatures.h"
@@ -474,15 +475,61 @@ decodeFixedType(ArrayRef<llvm::Intrinsic::IITDescriptor> &infos,
   switch (descriptor.Kind) {
   case IITDescriptor::Void:
     return VoidType::get(context);
-  case IITDescriptor::Integer:
-    return IntType::get(context, descriptor.Integer_Width, /*signed=*/true);
+  case IITDescriptor::VarArg:
+    llvm_unreachable("NYI: IITDescriptor::VarArg");
+  case IITDescriptor::MMX:
+    llvm_unreachable("NYI: IITDescriptor::MMX");
+  case IITDescriptor::Token:
+    llvm_unreachable("NYI: IITDescriptor::Token");
+  case IITDescriptor::Metadata:
+    llvm_unreachable("NYI: IITDescriptor::Metadata");
+  case IITDescriptor::Half:
+    return FP16Type::get(context);
+  case IITDescriptor::BFloat:
+    return BF16Type::get(context);
   case IITDescriptor::Float:
     return SingleType::get(context);
   case IITDescriptor::Double:
     return DoubleType::get(context);
-  default:
-    llvm_unreachable("NYI");
-  }
+  case IITDescriptor::Quad:
+    llvm_unreachable("NYI: IITDescriptor::Quad");
+  case IITDescriptor::Integer:
+    return IntType::get(context, descriptor.Integer_Width, /*isSigned=*/true);
+  case IITDescriptor::Vector: {
+    mlir::Type elementType = decodeFixedType(infos, context);
+    unsigned numElements = descriptor.Vector_Width.getFixedValue();
+    return cir::VectorType::get(context, elementType, numElements);
+  }
+  case IITDescriptor::Pointer:
+    llvm_unreachable("NYI: IITDescriptor::Pointer");
+  case IITDescriptor::Struct:
+    llvm_unreachable("NYI: IITDescriptor::Struct");
+  case IITDescriptor::Argument:
+    llvm_unreachable("NYI: IITDescriptor::Argument");
+  case IITDescriptor::ExtendArgument:
+    llvm_unreachable("NYI: IITDescriptor::ExtendArgument");
+  case IITDescriptor::TruncArgument:
+    llvm_unreachable("NYI: IITDescriptor::TruncArgument");
+  case IITDescriptor::OneNthEltsVecArgument:
+    llvm_unreachable("NYI: IITDescriptor::OneNthEltsVecArgument");
+  case IITDescriptor::SameVecWidthArgument:
+    llvm_unreachable("NYI: IITDescriptor::SameVecWidthArgument");
+  case IITDescriptor::VecOfAnyPtrsToElt:
+    llvm_unreachable("NYI: IITDescriptor::VecOfAnyPtrsToElt");
+  case IITDescriptor::Subdivide2Argument:
+    llvm_unreachable("NYI: IITDescriptor::Subdivide2Argument");
+  case IITDescriptor::Subdivide4Argument:
+    llvm_unreachable("NYI: IITDescriptor::Subdivide4Argument");
+  case IITDescriptor::VecOfBitcastsToInt:
+    llvm_unreachable("NYI: IITDescriptor::VecOfBitcastsToInt");
+  case IITDescriptor::AMX:
+    llvm_unreachable("NYI: IITDescriptor::AMX");
+  case IITDescriptor::PPCQuad:
+    llvm_unreachable("NYI: IITDescriptor::PPCQuad");
+  case IITDescriptor::AArch64Svcount:
+    llvm_unreachable("NYI: IITDescriptor::AArch64Svcount");
+  }
+  llvm_unreachable("Unknown builtin: Must return from switch");
 }
 
 // llvm::Intrinsics accepts only LLVMContext. We need to reimplement it here.