[RISCV] Share ArgGPRs array between SelectionDAG and GISel. (#74152)

This will allow us to isolate the EABI from D70401 to this new function.

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

@@ -423,10 +423,6 @@ bool RISCVCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
   return true;
 }
 
-static const MCPhysReg ArgGPRs[] = {RISCV::X10, RISCV::X11, RISCV::X12,
-                                    RISCV::X13, RISCV::X14, RISCV::X15,
-                                    RISCV::X16, RISCV::X17};
-
 /// If there are varargs that were passed in a0-a7, the data in those registers
 /// must be copied to the varargs save area on the stack.
 void RISCVCallLowering::saveVarArgRegisters(
@@ -435,7 +431,7 @@ void RISCVCallLowering::saveVarArgRegisters(
   MachineFunction &MF = MIRBuilder.getMF();
   const RISCVSubtarget &Subtarget = MF.getSubtarget<RISCVSubtarget>();
   unsigned XLenInBytes = Subtarget.getXLen() / 8;
-  ArrayRef<MCPhysReg> ArgRegs(ArgGPRs);
+  ArrayRef<MCPhysReg> ArgRegs = RISCV::getArgGPRs();
   unsigned Idx = CCInfo.getFirstUnallocated(ArgRegs);
 
   // Offset of the first variable argument from stack pointer, and size of

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -16844,10 +16844,6 @@ void RISCVTargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
 // register-size fields in the same situations they would be for fixed
 // arguments.
 
-static const MCPhysReg ArgGPRs[] = {
-  RISCV::X10, RISCV::X11, RISCV::X12, RISCV::X13,
-  RISCV::X14, RISCV::X15, RISCV::X16, RISCV::X17
-};
 static const MCPhysReg ArgFPR16s[] = {
   RISCV::F10_H, RISCV::F11_H, RISCV::F12_H, RISCV::F13_H,
   RISCV::F14_H, RISCV::F15_H, RISCV::F16_H, RISCV::F17_H
@@ -16872,13 +16868,22 @@ static const MCPhysReg ArgVRM4s[] = {RISCV::V8M4, RISCV::V12M4, RISCV::V16M4,
                                      RISCV::V20M4};
 static const MCPhysReg ArgVRM8s[] = {RISCV::V8M8, RISCV::V16M8};
 
+ArrayRef<MCPhysReg> RISCV::getArgGPRs() {
+  static const MCPhysReg ArgGPRs[] = {RISCV::X10, RISCV::X11, RISCV::X12,
+                                      RISCV::X13, RISCV::X14, RISCV::X15,
+                                      RISCV::X16, RISCV::X17};
+
+  return ArrayRef(ArgGPRs);
+}
+
 // Pass a 2*XLEN argument that has been split into two XLEN values through
 // registers or the stack as necessary.
 static bool CC_RISCVAssign2XLen(unsigned XLen, CCState &State, CCValAssign VA1,
                                 ISD::ArgFlagsTy ArgFlags1, unsigned ValNo2,
                                 MVT ValVT2, MVT LocVT2,
                                 ISD::ArgFlagsTy ArgFlags2) {
   unsigned XLenInBytes = XLen / 8;
+  ArrayRef<MCPhysReg> ArgGPRs = RISCV::getArgGPRs();
   if (Register Reg = State.AllocateReg(ArgGPRs)) {
     // At least one half can be passed via register.
     State.addLoc(CCValAssign::getReg(VA1.getValNo(), VA1.getValVT(), Reg,
@@ -16999,6 +17004,8 @@ bool RISCV::CC_RISCV(const DataLayout &DL, RISCVABI::ABI ABI, unsigned ValNo,
     LocInfo = CCValAssign::BCvt;
   }
 
+  ArrayRef<MCPhysReg> ArgGPRs = RISCV::getArgGPRs();
+
   // If this is a variadic argument, the RISC-V calling convention requires
   // that it is assigned an 'even' or 'aligned' register if it has 8-byte
   // alignment (RV32) or 16-byte alignment (RV64). An aligned register should
@@ -17684,7 +17691,7 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
     MF.getInfo<RISCVMachineFunctionInfo>()->setIsVectorCall();
 
   if (IsVarArg) {
-    ArrayRef<MCPhysReg> ArgRegs = ArrayRef(ArgGPRs);
+    ArrayRef<MCPhysReg> ArgRegs = RISCV::getArgGPRs();
     unsigned Idx = CCInfo.getFirstUnallocated(ArgRegs);
     const TargetRegisterClass *RC = &RISCV::GPRRegClass;
     MachineFrameInfo &MFI = MF.getFrameInfo();

llvm/lib/Target/RISCV/RISCVISelLowering.h

@@ -986,6 +986,9 @@ bool CC_RISCV_FastCC(const DataLayout &DL, RISCVABI::ABI ABI, unsigned ValNo,
 bool CC_RISCV_GHC(unsigned ValNo, MVT ValVT, MVT LocVT,
                   CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
                   CCState &State);
+
+ArrayRef<MCPhysReg> getArgGPRs();
+
 } // end namespace RISCV
 
 namespace RISCVVIntrinsicsTable {