PR2985 / <rdar://problem/6584986>

When compiling in Thumb mode, only the low (R0-R7) registers are available
for most instructions. Breaking the low registers into a new register class
handles this. Uses of R12, SP, etc, are handled explicitly where needed
with copies inserted to move results into low registers where the rest of
the code generator can deal with them.

llvm-svn: 68545

1 files changed, 36 insertions, 9 deletions

diff --git a/llvm/lib/Target/ARM/ARMRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMRegisterInfo.cpp
index b220b3bb2b8..2fae432633b 100644
--- a/llvm/lib/Target/ARM/ARMRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMRegisterInfo.cpp
@@ -211,6 +211,22 @@ bool ARMRegisterInfo::isLowRegister(unsigned Reg) const {
   }
 }
 
+const TargetRegisterClass*
+ARMRegisterInfo::getPhysicalRegisterRegClass(unsigned Reg, MVT VT) const {
+  if (STI.isThumb()) {
+    if (isLowRegister(Reg))
+      return ARM::tGPRRegisterClass;
+    switch (Reg) {
+    default:
+      break;
+    case ARM::R8:  case ARM::R9:  case ARM::R10:  case ARM::R11:
+    case ARM::R12: case ARM::SP:  case ARM::LR:   case ARM::PC:
+      return ARM::GPRRegisterClass;
+    }
+  }
+  return TargetRegisterInfo::getPhysicalRegisterRegClass(Reg, VT);
+}
+
 const unsigned*
 ARMRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
   static const unsigned CalleeSavedRegs[] = {
@@ -244,7 +260,16 @@ ARMRegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
     &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass,
     0
   };
-  return CalleeSavedRegClasses;
+  static const TargetRegisterClass * const ThumbCalleeSavedRegClasses[] = {
+    &ARM::GPRRegClass, &ARM::GPRRegClass, &ARM::GPRRegClass,
+    &ARM::GPRRegClass, &ARM::GPRRegClass, &ARM::tGPRRegClass,
+    &ARM::tGPRRegClass,&ARM::tGPRRegClass,&ARM::tGPRRegClass,
+
+    &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass,
+    &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass, &ARM::DPRRegClass,
+    0
+  };
+  return STI.isThumb() ? ThumbCalleeSavedRegClasses : CalleeSavedRegClasses;
 }
 
 BitVector ARMRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
@@ -400,7 +425,7 @@ void emitThumbRegPlusImmInReg(MachineBasicBlock &MBB,
     if (DestReg == ARM::SP) {
       assert(BaseReg == ARM::SP && "Unexpected!");
       LdReg = ARM::R3;
-      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R12)
+      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVlor2hir), ARM::R12)
         .addReg(ARM::R3, false, false, true);
     }
 
@@ -423,7 +448,7 @@ void emitThumbRegPlusImmInReg(MachineBasicBlock &MBB,
     else
       MIB.addReg(LdReg).addReg(BaseReg, false, false, true);
     if (DestReg == ARM::SP)
-      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R3)
+      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVhir2lor), ARM::R3)
         .addReg(ARM::R12, false, false, true);
 }
 
@@ -616,6 +641,7 @@ static
 unsigned findScratchRegister(RegScavenger *RS, const TargetRegisterClass *RC,
                              ARMFunctionInfo *AFI) {
   unsigned Reg = RS ? RS->FindUnusedReg(RC, true) : (unsigned) ARM::R12;
+  assert (!AFI->isThumbFunction());
   if (Reg == 0)
     // Try a already spilled CS register.
     Reg = RS->FindUnusedReg(RC, AFI->getSpilledCSRegisters());
@@ -717,7 +743,7 @@ void ARMRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
 
     if (Offset == 0) {
       // Turn it into a move.
-      MI.setDesc(TII.get(ARM::tMOVr));
+      MI.setDesc(TII.get(ARM::tMOVhir2lor));
       MI.getOperand(i).ChangeToRegister(FrameReg, false);
       MI.RemoveOperand(i+1);
       return;
@@ -891,12 +917,12 @@ void ARMRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
       unsigned TmpReg = ARM::R3;
       bool UseRR = false;
       if (ValReg == ARM::R3) {
-        BuildMI(MBB, II, dl, TII.get(ARM::tMOVr), ARM::R12)
+        BuildMI(MBB, II, dl, TII.get(ARM::tMOVlor2hir), ARM::R12)
           .addReg(ARM::R2, false, false, true);
         TmpReg = ARM::R2;
       }
       if (TmpReg == ARM::R3 && AFI->isR3LiveIn())
-        BuildMI(MBB, II, dl, TII.get(ARM::tMOVr), ARM::R12)
+        BuildMI(MBB, II, dl, TII.get(ARM::tMOVlor2hir), ARM::R12)
           .addReg(ARM::R3, false, false, true);
       if (Opcode == ARM::tSpill) {
         if (FrameReg == ARM::SP)
@@ -919,10 +945,10 @@ void ARMRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
 
       MachineBasicBlock::iterator NII = next(II);
       if (ValReg == ARM::R3)
-        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVr), ARM::R2)
+        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVhir2lor), ARM::R2)
           .addReg(ARM::R12, false, false, true);
       if (TmpReg == ARM::R3 && AFI->isR3LiveIn())
-        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVr), ARM::R3)
+        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVhir2lor), ARM::R3)
           .addReg(ARM::R12, false, false, true);
     } else
       assert(false && "Unexpected opcode!");
@@ -1401,7 +1427,8 @@ void ARMRegisterInfo::emitEpilogue(MachineFunction &MF,
           emitThumbRegPlusImmediate(MBB, MBBI, ARM::SP, FramePtr, -NumBytes,
                                     TII, *this, dl);
         else
-          BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP).addReg(FramePtr);
+          BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVlor2hir), ARM::SP)
+            .addReg(FramePtr);
       } else {
         if (MBBI->getOpcode() == ARM::tBX_RET &&
             &MBB.front() != MBBI &&