[Subzero][MIPS32] Adds prolog instructions for MIPS32

src/IceTargetLoweringMIPS32.h

Index: src/IceTargetLoweringMIPS32.h
diff --git a/src/IceTargetLoweringMIPS32.h b/src/IceTargetLoweringMIPS32.h
index 3366dcea677cec844f82fdebbc75e05d8250ee9f..e45a07fc6ca0351a853c5189e740499f3a365a5d 100644
--- a/src/IceTargetLoweringMIPS32.h
+++ b/src/IceTargetLoweringMIPS32.h
@@ -447,6 +447,11 @@ public:
   static Type stackSlotType();
   Variable *copyToReg(Operand *Src, RegNumT RegNum = RegNumT());
 
+  // Iterates over the CFG and determines the maximum outgoing stack arguments
+  // bytes. This information is later used during addProlog() to pre-allocate
+  // the outargs area
+  void findMaxStackOutArgsSize();
+
   void addProlog(CfgNode *Node) override;
   void addEpilog(CfgNode *Node) override;
 
@@ -457,6 +462,9 @@ public:
   Operand *loOperand(Operand *Operand);
   Operand *hiOperand(Operand *Operand);
 
+  void finishArgumentLowering(Variable *Arg, Variable *FramePtr,
+                              size_t BasicFrameOffset, size_t *InArgsSizeBytes);
+
   Operand *legalizeUndef(Operand *From, RegNumT RegNum = RegNumT());
 
 protected:
@@ -506,13 +514,18 @@ protected:
 
   bool UsesFramePointer = false;
   bool NeedsStackAlignment = false;
+  bool MaybeLeafFunc = true;
+  bool PrologEmitsFixedAllocas = false;
+  uint32_t MaxOutArgsSizeBytes = 0;
   static SmallBitVector TypeToRegisterSet[RCMIPS32_NUM];
   static SmallBitVector TypeToRegisterSetUnfiltered[RCMIPS32_NUM];
   static SmallBitVector RegisterAliases[RegMIPS32::Reg_NUM];
   SmallBitVector RegsUsed;
   VarList PhysicalRegisters[IceType_NUM];
+  VarList PreservedGPRs;
   static constexpr uint32_t CHAR_BITS = 8;
   static constexpr uint32_t INT32_BITS = 32;
+  size_t SpillAreaSizeBytes = 0;
 
 private:
   ENABLE_MAKE_UNIQUE;