Turn on register scavenger for Mips 16

We use an unused Mips 32 register for the emergency slot
instead of using the stack.

llvm-svn: 170665

llvm/lib/Target/Mips/Mips16RegisterInfo.cpp

@@ -43,6 +43,32 @@ Mips16RegisterInfo::Mips16RegisterInfo(const MipsSubtarget &ST,
     const Mips16InstrInfo &I)
   : MipsRegisterInfo(ST), TII(I) {}
 
+bool Mips16RegisterInfo::requiresRegisterScavenging
+  (const MachineFunction &MF) const {
+  return true;
+}
+bool Mips16RegisterInfo::requiresFrameIndexScavenging
+  (const MachineFunction &MF) const {
+  return true;
+}
+
+bool Mips16RegisterInfo::useFPForScavengingIndex
+  (const MachineFunction &MF) const {
+  return false;
+}
+
+bool Mips16RegisterInfo::saveScavengerRegister
+  (MachineBasicBlock &MBB,
+   MachineBasicBlock::iterator I,
+   MachineBasicBlock::iterator &UseMI,
+   const TargetRegisterClass *RC,
+   unsigned Reg) const {
+  DebugLoc DL;
+  TII.copyPhysReg(MBB, I, DL, Mips::T0, Reg, true);
+  TII.copyPhysReg(MBB, UseMI, DL, Reg, Mips::T0, true);
+  return true;
+}
+
 // This function eliminate ADJCALLSTACKDOWN,
 // ADJCALLSTACKUP pseudo instructions
 void Mips16RegisterInfo::

llvm/lib/Target/Mips/Mips16RegisterInfo.h

@@ -27,6 +27,19 @@ public:
   void eliminateCallFramePseudoInstr(MachineFunction &MF,
                                      MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator I) const;
+
+  bool requiresRegisterScavenging(const MachineFunction &MF) const;
+
+  bool requiresFrameIndexScavenging(const MachineFunction &MF) const;
+
+  bool useFPForScavengingIndex(const MachineFunction &MF) const;
+
+  bool saveScavengerRegister(MachineBasicBlock &MBB,
+                                     MachineBasicBlock::iterator I,
+                                     MachineBasicBlock::iterator &UseMI,
+                                     const TargetRegisterClass *RC,
+                                     unsigned Reg) const;
+
 private:
   virtual void eliminateFI(MachineBasicBlock::iterator II, unsigned OpNo,
                            int FrameIndex, uint64_t StackSize,