Properly save and restore RA and Mips16 callee save registers S0,S1

Patch by Reed Kotler.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164349 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/Mips16FrameLowering.cpp

@@ -66,7 +66,42 @@ spillCalleeSavedRegisters(MachineBasicBlock &MBB,
                           MachineBasicBlock::iterator MI,
                           const std::vector<CalleeSavedInfo> &CSI,
                           const TargetRegisterInfo *TRI) const {
-  // FIXME: implement.
+  MachineFunction *MF = MBB.getParent();
+  MachineBasicBlock *EntryBlock = MF->begin();
+  const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
+
+  //
+  // Registers RA, S0,S1 are the callee saved registers and they
+  // will be saved with the "save" instruction
+  // during emitPrologue
+  //
+  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
+    // Add the callee-saved register as live-in. Do not add if the register is
+    // RA and return address is taken, because it has already been added in
+    // method MipsTargetLowering::LowerRETURNADDR.
+    // It's killed at the spill, unless the register is RA and return address
+    // is taken.
+    unsigned Reg = CSI[i].getReg();
+    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
+      && MF->getFrameInfo()->isReturnAddressTaken();
+    if (!IsRAAndRetAddrIsTaken)
+      EntryBlock->addLiveIn(Reg);
+  }
+
+  return true;
+}
+
+bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                          MachineBasicBlock::iterator MI,
+                                       const std::vector<CalleeSavedInfo> &CSI,
+                                       const TargetRegisterInfo *TRI) const {
+  //
+  // Registers RA,S0,S1 are the callee saved registers and they will be restored
+  // with the restore instruction during emitEpilogue.
+  // We need to override this virtual function, otherwise llvm will try and
+  // restore the registers on it's on from the stack.
+  //
+
   return true;
 }
 
@@ -79,6 +114,9 @@ Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
 void Mips16FrameLowering::
 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                      RegScavenger *RS) const {
+  MF.getRegInfo().setPhysRegUsed(Mips::RA);
+  MF.getRegInfo().setPhysRegUsed(Mips::S0);
+  MF.getRegInfo().setPhysRegUsed(Mips::S1);
 }
 
 const MipsFrameLowering *

lib/Target/Mips/Mips16FrameLowering.h

@@ -32,6 +32,11 @@ public:
                                  const std::vector<CalleeSavedInfo> &CSI,
                                  const TargetRegisterInfo *TRI) const;
 
+  bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                   MachineBasicBlock::iterator MI,
+                                   const std::vector<CalleeSavedInfo> &CSI,
+                                   const TargetRegisterInfo *TRI) const;
+
   bool hasReservedCallFrame(const MachineFunction &MF) const;
 
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,

lib/Target/Mips/Mips16InstrInfo.td

@@ -254,10 +254,12 @@ def OrRxRxRy16: FRxRxRy16_ins<0b01101, "or", IIAlu>, ArithLogic16Defs<1>;
 // for direct object emitter, encoding needs to be adjusted for the
 // frame size
 //
-let ra=1, s=0,s0=0,s1=0 in
+let ra=1, s=0,s0=1,s1=1 in
 def RestoreRaF16:
   FI8_SVRS16<0b1, (outs), (ins uimm16:$frame_size),
-             "restore \t$$ra, $frame_size", [], IILoad >;
+             "restore \t$$ra,  $$s0, $$s1, $frame_size", [], IILoad > {
+  let isCodeGenOnly = 1;
+}
 
 //
 // Format: SAVE {ra,}{s0/s1/s0-1,}{framesize} (All arguments are optional)
@@ -266,11 +268,12 @@ def RestoreRaF16:
 // To set up a stack frame on entry to a subroutine,
 // saving return address and static registers, and adjusting stack
 //
-let ra=1, s=1,s0=0,s1=0 in
+let ra=1, s=1,s0=1,s1=1 in
 def SaveRaF16:
   FI8_SVRS16<0b1, (outs), (ins uimm16:$frame_size),
-             "save \t$$ra, $frame_size", [], IILoad >;
+             "save \t$$ra, $$s0, $$s1, $frame_size", [], IILoad > {
-
+  let isCodeGenOnly = 1;
+}
 //
 // Format: SB ry, offset(rx) MIPS16e
 // Purpose: Store Byte (Extended)