[Subzero][MIPS] Implement conditional branches and integer comparisons

src/IceTargetLoweringMIPS32.h

Index: src/IceTargetLoweringMIPS32.h
diff --git a/src/IceTargetLoweringMIPS32.h b/src/IceTargetLoweringMIPS32.h
index ea062e7d7d799f4c4495383adbb84e5f951f9d4e..54e07fab902b519ac160f0ecada2dedd8451c85f 100644
--- a/src/IceTargetLoweringMIPS32.h
+++ b/src/IceTargetLoweringMIPS32.h
@@ -220,10 +220,22 @@ public:
     Context.insert<InstMIPS32Sub>(Dest, Src0, Src1);
   }
 
-  void _sltu(Variable *Dest, Variable *Src0, Variable *Src1) {
-    Context.insert<InstMIPS32Sltu>(Dest, Src0, Src1);
+  void _slt(Variable *Dest, Variable *Src0, Variable *Src1) {
+     Context.insert<InstMIPS32Slt>(Dest, Src0, Src1);
+   }
+
+  void _slti(Variable *Dest, Variable *Src, uint32_t Imm) {
+    Context.insert<InstMIPS32Slti>(Dest, Src, Imm);
   }
 
+  void _sltiu(Variable *Dest, Variable *Src, uint32_t Imm) {
+    Context.insert<InstMIPS32Sltiu>(Dest, Src, Imm);
+  }
+
+  void _sltu(Variable *Dest, Variable *Src0, Variable *Src1) {
+     Context.insert<InstMIPS32Sltu>(Dest, Src0, Src1);
+   }
+
   void _subu(Variable *Dest, Variable *Src0, Variable *Src1) {
     Context.insert<InstMIPS32Subu>(Dest, Src0, Src1);
   }
@@ -232,6 +244,10 @@ public:
     Context.insert<InstMIPS32Xor>(Dest, Src0, Src1);
   }
 
+  void _xori(Variable *Dest, Variable *Src, uint32_t Imm) {
+     Context.insert<InstMIPS32Xori>(Dest, Src, Imm);
+   }
+
   void lowerArguments() override;
 
   /// Operand legalization helpers.  To deal with address mode constraints,
@@ -257,6 +273,10 @@ public:
 
   Variable *makeReg(Type Ty, RegNumT RegNum = RegNumT());
 
+  Variable *getZero() {
+    return getPhysicalRegister(RegMIPS32::Reg_ZERO, IceType_i32);
+  }
+
   Variable *I32Reg(RegNumT RegNum = RegNumT()) {
     return makeReg(IceType_i32, RegNum);
   }
@@ -293,6 +313,7 @@ protected:
   void lowerExtractElement(const InstExtractElement *Instr) override;
   void lowerFcmp(const InstFcmp *Instr) override;
   void lowerIcmp(const InstIcmp *Instr) override;
+  void lower64Icmp(const InstIcmp *Instr);
   void lowerIntrinsicCall(const InstIntrinsicCall *Instr) override;
   void lowerInsertElement(const InstInsertElement *Instr) override;
   void lowerLoad(const InstLoad *Instr) override;