[RISCV][GISel] Add calling convention support for half (#94110)

This patch adds initial support to the half type on RISC-V.

Author: dtcxzyw

llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp

@@ -340,7 +340,7 @@ static bool isSupportedArgumentType(Type *T, const RISCVSubtarget &Subtarget,
   // supported yet.
   if (T->isIntegerTy())
     return T->getIntegerBitWidth() <= Subtarget.getXLen() * 2;
-  if (T->isFloatTy() || T->isDoubleTy())
+  if (T->isHalfTy() || T->isFloatTy() || T->isDoubleTy())
     return true;
   if (T->isPointerTy())
     return true;
@@ -361,7 +361,7 @@ static bool isSupportedReturnType(Type *T, const RISCVSubtarget &Subtarget,
   // supported yet.
   if (T->isIntegerTy())
     return T->getIntegerBitWidth() <= Subtarget.getXLen() * 2;
-  if (T->isFloatTy() || T->isDoubleTy())
+  if (T->isHalfTy() || T->isFloatTy() || T->isDoubleTy())
     return true;
   if (T->isPointerTy())
     return true;

llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp

@@ -849,6 +849,8 @@ const TargetRegisterClass *RISCVInstructionSelector::getRegClassForTypeOnBank(
   }
 
   if (RB.getID() == RISCV::FPRBRegBankID) {
+    if (Ty.getSizeInBits() == 16)
+      return &RISCV::FPR16RegClass;
     if (Ty.getSizeInBits() == 32)
       return &RISCV::FPR32RegClass;
     if (Ty.getSizeInBits() == 64)