[Subzero][MIPS32] Add argument handling in LowerCall

src/IceTargetLoweringMIPS32.h

Index: src/IceTargetLoweringMIPS32.h
diff --git a/src/IceTargetLoweringMIPS32.h b/src/IceTargetLoweringMIPS32.h
index aca82cd50d71bddb9b0d65d234e84241367a62ea..b0f5202bc4268cf41f377f55ef20f4672acab265 100644
--- a/src/IceTargetLoweringMIPS32.h
+++ b/src/IceTargetLoweringMIPS32.h
@@ -397,6 +397,29 @@ public:
 
   Operand *legalizeUndef(Operand *From, RegNumT RegNum = RegNumT());
 
+  /// Helper class that understands the Calling Convention and register
+  /// assignments.
+  class CallingConv {
+    CallingConv(const CallingConv &) = delete;
+    CallingConv &operator=(const CallingConv &) = delete;
+
+  public:
+    CallingConv();
+    ~CallingConv() = default;
+
+    /// argInGPR returns true if there is a GPR available for the requested
+    /// type, and false otherwise. If it returns true, Reg is set to the
+    /// appropriate register number. Note that, when Ty == IceType_i64, Reg will
+    /// be an I64 register pair.
+    bool argInGPR(Type Ty, RegNumT *Reg);
+
+  private:
+    void discardUnavailableGPRsAndTheirAliases(CfgVector<RegNumT> *Regs);
+    SmallBitVector GPRegsUsed;
+    CfgVector<RegNumT> GPRArgs;
+    CfgVector<RegNumT> I64Args;
+  };
+
 protected:
   explicit TargetMIPS32(Cfg *Func);