[PowerPC][NFC] Update lowering STXVP to STXV in Oct word spilling

Simpliy handling for spilling of acc reg with stx by removing
explicit register arithmetic and clean up code gen for register
mapping used in stxvp spilling.

Author: lei137

llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp

@@ -1238,40 +1238,28 @@ static void emitAccSpillRestoreInfo(MachineBasicBlock &MBB, bool IsPrimed,
 #endif
 }
 
-static void spillRegPairs(MachineBasicBlock &MBB,
-                          MachineBasicBlock::iterator II, DebugLoc DL,
-                          const TargetInstrInfo &TII, Register SrcReg,
-                          unsigned FrameIndex, bool IsLittleEndian,
-                          bool IsKilled, bool TwoPairs) {
-  unsigned Offset = 0;
-  // The register arithmetic in this function does not support virtual
-  // registers.
-  assert(!SrcReg.isVirtual() &&
+void PPCRegisterInfo::spillRegPair(MachineBasicBlock &MBB,
+                                   MachineBasicBlock::iterator II, DebugLoc DL,
+                                   const TargetInstrInfo &TII,
+                                   unsigned FrameIndex, bool IsLittleEndian,
+                                   bool IsKilled, Register Reg,
+                                   int Offset) const {
+
+  // This function does not support virtual registers.
+  assert(!Reg.isVirtual() &&
          "Spilling register pairs does not support virtual registers.");
 
-  if (TwoPairs)
-    Offset = IsLittleEndian ? 48 : 0;
-  else
-    Offset = IsLittleEndian ? 16 : 0;
-  Register Reg = (SrcReg > PPC::VSRp15) ? PPC::V0 + (SrcReg - PPC::VSRp16) * 2
-                                        : PPC::VSL0 + (SrcReg - PPC::VSRp0) * 2;
-  addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXV))
-                        .addReg(Reg, getKillRegState(IsKilled)),
-                    FrameIndex, Offset);
-  Offset += IsLittleEndian ? -16 : 16;
-  addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXV))
-                        .addReg(Reg + 1, getKillRegState(IsKilled)),
-                    FrameIndex, Offset);
-  if (TwoPairs) {
-    Offset += IsLittleEndian ? -16 : 16;
-    addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXV))
-                          .addReg(Reg + 2, getKillRegState(IsKilled)),
-                      FrameIndex, Offset);
-    Offset += IsLittleEndian ? -16 : 16;
-    addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXV))
-                          .addReg(Reg + 3, getKillRegState(IsKilled)),
-                      FrameIndex, Offset);
-  }
+  addFrameReference(
+      BuildMI(MBB, II, DL, TII.get(PPC::STXV))
+          .addReg(TargetRegisterInfo::getSubReg(Reg, PPC::sub_vsx0),
+                  getKillRegState(IsKilled)),
+      FrameIndex, Offset);
+
+  addFrameReference(
+      BuildMI(MBB, II, DL, TII.get(PPC::STXV))
+          .addReg(TargetRegisterInfo::getSubReg(Reg, PPC::sub_vsx1),
+                  getKillRegState(IsKilled)),
+      FrameIndex, IsLittleEndian ? Offset - 16 : Offset + 16);
 }
 
 /// Remove any STXVP[X] instructions and split them out into a pair of
@@ -1290,8 +1278,10 @@ void PPCRegisterInfo::lowerOctWordSpilling(MachineBasicBlock::iterator II,
   Register SrcReg = MI.getOperand(0).getReg();
   bool IsLittleEndian = Subtarget.isLittleEndian();
   bool IsKilled = MI.getOperand(0).isKill();
-  spillRegPairs(MBB, II, DL, TII, SrcReg, FrameIndex, IsLittleEndian, IsKilled,
-                /* TwoPairs */ false);
+
+  spillRegPair(MBB, II, DL, TII, FrameIndex, IsLittleEndian, IsKilled, SrcReg,
+               IsLittleEndian ? 16 : 0);
+
   // Discard the original instruction.
   MBB.erase(II);
 }
@@ -1325,8 +1315,6 @@ void PPCRegisterInfo::lowerACCSpilling(MachineBasicBlock::iterator II,
   bool IsKilled = MI.getOperand(0).isKill();
 
   bool IsPrimed = PPC::ACCRCRegClass.contains(SrcReg);
-  Register Reg =
-      PPC::VSRp0 + (SrcReg - (IsPrimed ? PPC::ACC0 : PPC::UACC0)) * 2;
   bool IsLittleEndian = Subtarget.isLittleEndian();
 
   emitAccSpillRestoreInfo(MBB, IsPrimed, false);
@@ -1337,16 +1325,24 @@ void PPCRegisterInfo::lowerACCSpilling(MachineBasicBlock::iterator II,
   // adjust the offset of the store that is within the 64-byte stack slot.
   if (IsPrimed)
     BuildMI(MBB, II, DL, TII.get(PPC::XXMFACC), SrcReg).addReg(SrcReg);
-  if (DisableAutoPairedVecSt)
-    spillRegPairs(MBB, II, DL, TII, Reg, FrameIndex, IsLittleEndian, IsKilled,
-                  /* TwoPairs */ true);
-  else {
-    addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXVP))
-                          .addReg(Reg, getKillRegState(IsKilled)),
-                      FrameIndex, IsLittleEndian ? 32 : 0);
-    addFrameReference(BuildMI(MBB, II, DL, TII.get(PPC::STXVP))
-                          .addReg(Reg + 1, getKillRegState(IsKilled)),
-                      FrameIndex, IsLittleEndian ? 0 : 32);
+  if (DisableAutoPairedVecSt) {
+    spillRegPair(MBB, II, DL, TII, FrameIndex, IsLittleEndian, IsKilled,
+                 TargetRegisterInfo::getSubReg(SrcReg, PPC::sub_pair0),
+                 IsLittleEndian ? 48 : 0);
+    spillRegPair(MBB, II, DL, TII, FrameIndex, IsLittleEndian, IsKilled,
+                 TargetRegisterInfo::getSubReg(SrcReg, PPC::sub_pair1),
+                 IsLittleEndian ? 16 : 32);
+  } else {
+    addFrameReference(
+        BuildMI(MBB, II, DL, TII.get(PPC::STXVP))
+            .addReg(TargetRegisterInfo::getSubReg(SrcReg, PPC::sub_pair0),
+                    getKillRegState(IsKilled)),
+        FrameIndex, IsLittleEndian ? 32 : 0);
+    addFrameReference(
+        BuildMI(MBB, II, DL, TII.get(PPC::STXVP))
+            .addReg(TargetRegisterInfo::getSubReg(SrcReg, PPC::sub_pair1),
+                    getKillRegState(IsKilled)),
+        FrameIndex, IsLittleEndian ? 0 : 32);
   }
   if (IsPrimed && !IsKilled)
     BuildMI(MBB, II, DL, TII.get(PPC::XXMTACC), SrcReg).addReg(SrcReg);

llvm/lib/Target/PowerPC/PPCRegisterInfo.h

@@ -58,6 +58,11 @@ class PPCRegisterInfo : public PPCGenRegisterInfo {
   DenseMap<unsigned, unsigned> ImmToIdxMap;
   const PPCTargetMachine &TM;
 
+  void spillRegPair(MachineBasicBlock &MBB, MachineBasicBlock::iterator II,
+                    DebugLoc DL, const TargetInstrInfo &TII,
+                    unsigned FrameIndex, bool IsLittleEndian, bool IsKilled,
+                    Register Reg, int Offset) const;
+
 public:
   PPCRegisterInfo(const PPCTargetMachine &TM);