[PowerPC] More refactoring prior to real PPC emitPrologue/Epilogue changes.

(Patch committed on behalf of Mark Minich, whose log entry follows.)

This is a continuation of the refactorings performed in svn rev 188573
(see that rev's comments for more detail).

This is my stage 2 refactoring: I combined the emitPrologue() &
emitEpilogue() PPC32 & PPC64 code into a single flow, simplifying a
lot of the code since in essence the PPC32 & PPC64 code generation
logic is the same, only the instruction forms are different (in most
cases). This simplification is necessary because my functional changes
(yet to come) add significant complexity, and without the
simplification of my stage 2 refactoring, the overall complexity of
both emitPrologue() & emitEpilogue() would have become almost
intractable for most mortal programmers (like me).

This submission was intended to be a pure refactoring (no functional
changes whatsoever). However, in the process of combining the PPC32 &
PPC64 flows, I spotted a difference that I believe is a bug (see svn
rev 186478 line 863, or svn rev 188573 line 888): This line appears to
be restoring the BP with the original FP content, not the original BP
content. When I merged the 32-bit and 64-bit code, I used the
corresponding code from the 64-bit flow, which I believe uses the
correct offset (BPOffset) for this operation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188741 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 194 insertions, 271 deletions

diff --git a/lib/Target/PowerPC/PPCFrameLowering.cpp b/lib/Target/PowerPC/PPCFrameLowering.cpp
index 5161de8537..0ac2ceddcc 100644
--- a/lib/Target/PowerPC/PPCFrameLowering.cpp
+++ b/lib/Target/PowerPC/PPCFrameLowering.cpp
@@ -382,10 +382,36 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
   PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
   bool MustSaveLR = FI->mustSaveLR();
   const SmallVectorImpl<unsigned> &MustSaveCRs = FI->getMustSaveCRs();
-  // Do we have a frame pointer for this function?
+  // Do we have a frame pointer and/or base pointer for this function?
   bool HasFP = hasFP(MF);
   bool HasBP = RegInfo->hasBasePointer(MF);
 
+  unsigned SPReg       = isPPC64 ? PPC::X1  : PPC::R1;
+  unsigned BPReg       = isPPC64 ? PPC::X30 : PPC::R30;
+  unsigned FPReg       = isPPC64 ? PPC::X31 : PPC::R31;
+  unsigned LRReg       = isPPC64 ? PPC::LR8 : PPC::LR;
+  unsigned ScratchReg  = isPPC64 ? PPC::X0  : PPC::R0;
+  unsigned TempReg     = isPPC64 ? PPC::X12 : PPC::R12; // another scratch reg
+  //  ...(R12/X12 is volatile in both Darwin & SVR4, & can't be a function arg.)
+  const MCInstrDesc& MFLRInst = TII.get(isPPC64 ? PPC::MFLR8
+                                                : PPC::MFLR );
+  const MCInstrDesc& StoreInst = TII.get(isPPC64 ? PPC::STD
+                                                 : PPC::STW );
+  const MCInstrDesc& StoreUpdtInst = TII.get(isPPC64 ? PPC::STDU
+                                                     : PPC::STWU );
+  const MCInstrDesc& StoreUpdtIdxInst = TII.get(isPPC64 ? PPC::STDUX
+                                                        : PPC::STWUX);
+  const MCInstrDesc& LoadImmShiftedInst = TII.get(isPPC64 ? PPC::LIS8
+                                                          : PPC::LIS );
+  const MCInstrDesc& OrImmInst = TII.get(isPPC64 ? PPC::ORI8
+                                                 : PPC::ORI );
+  const MCInstrDesc& OrInst = TII.get(isPPC64 ? PPC::OR8
+                                              : PPC::OR );
+  const MCInstrDesc& SubtractCarryingInst = TII.get(isPPC64 ? PPC::SUBFC8
+                                                            : PPC::SUBFC);
+  const MCInstrDesc& SubtractImmCarryingInst = TII.get(isPPC64 ? PPC::SUBFIC8
+                                                               : PPC::SUBFIC);
+
   // Regarding this assert: Even though LR is saved in the caller's frame (i.e.,
   // LROffset is positive), that slot is callee-owned. Because PPC32 SVR4 has no
   // Red Zone, an asynchronous event (a form of "callee") could claim a frame &
@@ -430,173 +456,106 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
   // indexed into with a simple STDU/STWU/STD/STW immediate offset operand.
   bool isLargeFrame = !isInt<16>(NegFrameSize);
 
-  if (isPPC64) {
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::MFLR8), PPC::X0);
+  if (MustSaveLR)
+    BuildMI(MBB, MBBI, dl, MFLRInst, ScratchReg);
 
-    if (!MustSaveCRs.empty()) {
-      MachineInstrBuilder MIB =
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::MFCR8), PPC::X12);
-      for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
-        MIB.addReg(MustSaveCRs[i], RegState::ImplicitKill);
-    }
+  assert((isPPC64 || MustSaveCRs.empty()) &&
+         "Prologue CR saving supported only in 64-bit mode");
 
-    if (HasFP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STD))
-        .addReg(PPC::X31)
-        .addImm(FPOffset)
-        .addReg(PPC::X1);
-
-    if (HasBP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STD))
-        .addReg(PPC::X30)
-        .addImm(BPOffset)
-        .addReg(PPC::X1);
-
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STD))
-        .addReg(PPC::X0)
-        .addImm(LROffset)
-        .addReg(PPC::X1);
-
-    if (!MustSaveCRs.empty())
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STW8))
-        .addReg(PPC::X12, getKillRegState(true))
-        .addImm(8)
-        .addReg(PPC::X1);
-  } else { // PPC32...
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::MFLR), PPC::R0);
-
-    if (HasFP)
-      // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STW))
-        .addReg(PPC::R31)
-        .addImm(FPOffset)
-        .addReg(PPC::R1);
-
-    if (HasBP)
-      // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STW))
-        .addReg(PPC::R30)
-        .addImm(BPOffset)
-        .addReg(PPC::R1);
-
-    assert(MustSaveCRs.empty() &&
-           "Prologue CR saving supported only in 64-bit mode");
-
-    if (MustSaveLR)
-      // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STW))
-        .addReg(PPC::R0)
-        .addImm(LROffset)
-        .addReg(PPC::R1);
+  if (!MustSaveCRs.empty()) { // will only occur for PPC64
+    MachineInstrBuilder MIB =
+      BuildMI(MBB, MBBI, dl, TII.get(PPC::MFCR8), TempReg);
+    for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
+      MIB.addReg(MustSaveCRs[i], RegState::ImplicitKill);
   }
 
+  if (HasFP)
+    // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
+    BuildMI(MBB, MBBI, dl, StoreInst)
+      .addReg(FPReg)
+      .addImm(FPOffset)
+      .addReg(SPReg);
+
+  if (HasBP)
+    // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
+    BuildMI(MBB, MBBI, dl, StoreInst)
+      .addReg(BPReg)
+      .addImm(BPOffset)
+      .addReg(SPReg);
+
+  if (MustSaveLR)
+    // FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
+    BuildMI(MBB, MBBI, dl, StoreInst)
+      .addReg(ScratchReg)
+      .addImm(LROffset)
+      .addReg(SPReg);
+
+  if (!MustSaveCRs.empty()) // will only occur for PPC64
+    BuildMI(MBB, MBBI, dl, TII.get(PPC::STW8))
+      .addReg(TempReg, getKillRegState(true))
+      .addImm(8)
+      .addReg(SPReg);
+
   // Skip the rest if this is a leaf function & all spills fit in the Red Zone.
   if (!FrameSize) return;
 
   // Adjust stack pointer: r1 += NegFrameSize.
   // If there is a preferred stack alignment, align R1 now
-  if (!isPPC64) { // PPC32...
-    if (HasBP) {
-      // Save a copy of r1 as the base pointer.
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::OR), PPC::R30)
-        .addReg(PPC::R1)
-        .addReg(PPC::R1);
-    }
 
-    if (HasBP && MaxAlign > 1) {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::RLWINM), PPC::R0)
-        .addReg(PPC::R1)
+  if (HasBP) {
+    // Save a copy of r1 as the base pointer.
+    BuildMI(MBB, MBBI, dl, OrInst, BPReg)
+      .addReg(SPReg)
+      .addReg(SPReg);
+  }
+
+  if (HasBP && MaxAlign > 1) {
+    if (isPPC64)
+      BuildMI(MBB, MBBI, dl, TII.get(PPC::RLDICL), ScratchReg)
+        .addReg(SPReg)
+        .addImm(0)
+        .addImm(64 - Log2_32(MaxAlign));
+    else // PPC32...
+      BuildMI(MBB, MBBI, dl, TII.get(PPC::RLWINM), ScratchReg)
+        .addReg(SPReg)
         .addImm(0)
         .addImm(32 - Log2_32(MaxAlign))
         .addImm(31);
-      if (!isLargeFrame) {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::SUBFIC), PPC::R0)
-          .addReg(PPC::R0, RegState::Kill)
-          .addImm(NegFrameSize);
-      } else {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS), PPC::R12)
-          .addImm(NegFrameSize >> 16);
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI), PPC::R12)
-          .addReg(PPC::R12, RegState::Kill)
-          .addImm(NegFrameSize & 0xFFFF);
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::SUBFC), PPC::R0)
-          .addReg(PPC::R0, RegState::Kill)
-          .addReg(PPC::R12, RegState::Kill);
-      }
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STWUX), PPC::R1)
-        .addReg(PPC::R1, RegState::Kill)
-        .addReg(PPC::R1)
-        .addReg(PPC::R0);
-
-    } else if (!isLargeFrame) {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STWU), PPC::R1)
-        .addReg(PPC::R1)
-        .addImm(NegFrameSize)
-        .addReg(PPC::R1);
-
+    if (!isLargeFrame) {
+      BuildMI(MBB, MBBI, dl, SubtractImmCarryingInst, ScratchReg)
+        .addReg(ScratchReg, RegState::Kill)
+        .addImm(NegFrameSize);
     } else {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS), PPC::R0)
+      BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, TempReg)
         .addImm(NegFrameSize >> 16);
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI), PPC::R0)
-        .addReg(PPC::R0, RegState::Kill)
+      BuildMI(MBB, MBBI, dl, OrImmInst, TempReg)
+        .addReg(TempReg, RegState::Kill)
         .addImm(NegFrameSize & 0xFFFF);
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STWUX), PPC::R1)
-        .addReg(PPC::R1, RegState::Kill)
-        .addReg(PPC::R1)
-        .addReg(PPC::R0);
+      BuildMI(MBB, MBBI, dl, SubtractCarryingInst, ScratchReg)
+        .addReg(ScratchReg, RegState::Kill)
+        .addReg(TempReg, RegState::Kill);
     }
-  } else { // PPC64...
-    if (HasBP) {
-      // Save a copy of r1 as the base pointer.
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::OR8), PPC::X30)
-        .addReg(PPC::X1)
-        .addReg(PPC::X1);
-    }
-
-    if (HasBP && MaxAlign > 1) {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::RLDICL), PPC::X0)
-        .addReg(PPC::X1)
-        .addImm(0)
-        .addImm(64 - Log2_32(MaxAlign));
-      if (!isLargeFrame) {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::SUBFIC8), PPC::X0)
-          .addReg(PPC::X0, RegState::Kill)
-          .addImm(NegFrameSize);
-      } else {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS8), PPC::X12)
-          .addImm(NegFrameSize >> 16);
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI8), PPC::X12)
-          .addReg(PPC::X12, RegState::Kill)
-          .addImm(NegFrameSize & 0xFFFF);
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::SUBFC8), PPC::X0)
-          .addReg(PPC::X0, RegState::Kill)
-          .addReg(PPC::X12, RegState::Kill);
-      }
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STDUX), PPC::X1)
-        .addReg(PPC::X1, RegState::Kill)
-        .addReg(PPC::X1)
-        .addReg(PPC::X0);
+    BuildMI(MBB, MBBI, dl, StoreUpdtIdxInst, SPReg)
+      .addReg(SPReg, RegState::Kill)
+      .addReg(SPReg)
+      .addReg(ScratchReg);
 
-    } else if (!isLargeFrame) {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STDU), PPC::X1)
-        .addReg(PPC::X1)
-        .addImm(NegFrameSize)
-        .addReg(PPC::X1);
+  } else if (!isLargeFrame) {
+    BuildMI(MBB, MBBI, dl, StoreUpdtInst, SPReg)
+      .addReg(SPReg)
+      .addImm(NegFrameSize)
+      .addReg(SPReg);
 
-    } else {
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS8), PPC::X0)
-        .addImm(NegFrameSize >> 16);
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI8), PPC::X0)
-        .addReg(PPC::X0, RegState::Kill)
-        .addImm(NegFrameSize & 0xFFFF);
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::STDUX), PPC::X1)
-        .addReg(PPC::X1, RegState::Kill)
-        .addReg(PPC::X1)
-        .addReg(PPC::X0);
-    }
+  } else {
+    BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
+      .addImm(NegFrameSize >> 16);
+    BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
+      .addReg(ScratchReg, RegState::Kill)
+      .addImm(NegFrameSize & 0xFFFF);
+    BuildMI(MBB, MBBI, dl, StoreUpdtIdxInst, SPReg)
+      .addReg(SPReg, RegState::Kill)
+      .addReg(SPReg)
+      .addReg(ScratchReg);
   }
 
   // Add the "machine moves" for the instructions we generated above, but in
@@ -612,22 +571,19 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
         MCCFIInstruction::createDefCfaOffset(FrameLabel, NegFrameSize));
 
     if (HasFP) {
-      unsigned Reg = isPPC64 ? PPC::X31 : PPC::R31;
-      Reg = MRI->getDwarfRegNum(Reg, true);
+      unsigned Reg = MRI->getDwarfRegNum(FPReg, true);
       MMI.addFrameInst(
           MCCFIInstruction::createOffset(FrameLabel, Reg, FPOffset));
     }
 
     if (HasBP) {
-      unsigned Reg = isPPC64 ? PPC::X30 : PPC::R30;
-      Reg = MRI->getDwarfRegNum(Reg, true);
+      unsigned Reg = MRI->getDwarfRegNum(BPReg, true);
       MMI.addFrameInst(
           MCCFIInstruction::createOffset(FrameLabel, Reg, BPOffset));
     }
 
     if (MustSaveLR) {
-      unsigned Reg = isPPC64 ? PPC::LR8 : PPC::LR;
-      Reg = MRI->getDwarfRegNum(Reg, true);
+      unsigned Reg = MRI->getDwarfRegNum(LRReg, true);
       MMI.addFrameInst(
           MCCFIInstruction::createOffset(FrameLabel, Reg, LROffset));
     }
@@ -637,15 +593,9 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
 
   // If there is a frame pointer, copy R1 into R31
   if (HasFP) {
-    if (!isPPC64) { // PPC32...
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::OR), PPC::R31)
-        .addReg(PPC::R1)
-        .addReg(PPC::R1);
-    } else { // PPC64...
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::OR8), PPC::X31)
-        .addReg(PPC::X1)
-        .addReg(PPC::X1);
-    }
+    BuildMI(MBB, MBBI, dl, OrInst, FPReg)
+      .addReg(SPReg)
+      .addReg(SPReg);
 
     if (needsFrameMoves) {
       ReadyLabel = MMI.getContext().CreateTempSymbol();
@@ -653,8 +603,7 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
       // Mark effective beginning of when frame pointer is ready.
       BuildMI(MBB, MBBI, dl, TII.get(PPC::PROLOG_LABEL)).addSym(ReadyLabel);
 
-      unsigned Reg = isPPC64 ? PPC::X31 : PPC::R31;
-      Reg = MRI->getDwarfRegNum(Reg, true);
+      unsigned Reg = MRI->getDwarfRegNum(FPReg, true);
       MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister(ReadyLabel, Reg));
     }
   }
@@ -731,10 +680,28 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
   PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
   bool MustSaveLR = FI->mustSaveLR();
   const SmallVectorImpl<unsigned> &MustSaveCRs = FI->getMustSaveCRs();
-  // Do we have a frame pointer for this function?
+  // Do we have a frame pointer and/or base pointer for this function?
   bool HasFP = hasFP(MF);
   bool HasBP = RegInfo->hasBasePointer(MF);
 
+  unsigned SPReg      = isPPC64 ? PPC::X1  : PPC::R1;
+  unsigned BPReg      = isPPC64 ? PPC::X30 : PPC::R30;
+  unsigned FPReg      = isPPC64 ? PPC::X31 : PPC::R31;
+  unsigned ScratchReg  = isPPC64 ? PPC::X0  : PPC::R0;
+  unsigned TempReg     = isPPC64 ? PPC::X12 : PPC::R12; // another scratch reg
+  const MCInstrDesc& MTLRInst = TII.get( isPPC64 ? PPC::MTLR8
+                                                 : PPC::MTLR );
+  const MCInstrDesc& LoadInst = TII.get( isPPC64 ? PPC::LD
+                                                 : PPC::LWZ );
+  const MCInstrDesc& LoadImmShiftedInst = TII.get( isPPC64 ? PPC::LIS8
+                                                           : PPC::LIS );
+  const MCInstrDesc& OrImmInst = TII.get( isPPC64 ? PPC::ORI8
+                                                  : PPC::ORI );
+  const MCInstrDesc& AddImmInst = TII.get( isPPC64 ? PPC::ADDI8
+                                                   : PPC::ADDI );
+  const MCInstrDesc& AddInst = TII.get( isPPC64 ? PPC::ADD8
+                                                : PPC::ADD4 );
+
   int LROffset = PPCFrameLowering::getReturnSaveOffset(isPPC64, isDarwinABI);
 
   int FPOffset = 0;
@@ -790,106 +757,69 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
   if (FrameSize) {
     // In the prologue, the loaded (or persistent) stack pointer value is offset
     // by the STDU/STDUX/STWU/STWUX instruction.  Add this offset back now.
-    if (!isPPC64) {
-      // If this function contained a fastcc call and GuaranteedTailCallOpt is
-      // enabled (=> hasFastCall()==true) the fastcc call might contain a tail
-      // call which invalidates the stack pointer value in SP(0). So we use the
-      // value of R31 in this case.
-      if (FI->hasFastCall()) {
-        assert(HasFP && "Expecting a valid frame pointer.");
-        if (!isLargeFrame) {
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDI), PPC::R1)
-            .addReg(PPC::R31).addImm(FrameSize);
-        } else {
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS), PPC::R0)
-            .addImm(FrameSize >> 16);
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI), PPC::R0)
-            .addReg(PPC::R0, RegState::Kill)
-            .addImm(FrameSize & 0xFFFF);
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ADD4))
-            .addReg(PPC::R1)
-            .addReg(PPC::R31)
-            .addReg(PPC::R0);
-        }
-      } else if (!isLargeFrame && !HasBP &&
-                 !MFI->hasVarSizedObjects()) {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDI), PPC::R1)
-          .addReg(PPC::R1).addImm(FrameSize);
-      } else {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ),PPC::R1)
-          .addImm(0).addReg(PPC::R1);
-      }
-    } else { // PPC64...
-      if (FI->hasFastCall()) {
-        if (!isLargeFrame) {
-          assert(HasFP && "Expecting a valid frame pointer.");
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDI8), PPC::X1)
-            .addReg(PPC::X31).addImm(FrameSize);
-        } else {
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::LIS8), PPC::X0)
-            .addImm(FrameSize >> 16);
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ORI8), PPC::X0)
-            .addReg(PPC::X0, RegState::Kill)
-            .addImm(FrameSize & 0xFFFF);
-          BuildMI(MBB, MBBI, dl, TII.get(PPC::ADD8))
-            .addReg(PPC::X1)
-            .addReg(PPC::X31)
-            .addReg(PPC::X0);
-        }
-      } else if (!isLargeFrame && !HasBP &&
-            !MFI->hasVarSizedObjects()) {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDI8), PPC::X1)
-           .addReg(PPC::X1).addImm(FrameSize);
+
+    // If this function contained a fastcc call and GuaranteedTailCallOpt is
+    // enabled (=> hasFastCall()==true) the fastcc call might contain a tail
+    // call which invalidates the stack pointer value in SP(0). So we use the
+    // value of R31 in this case.
+    if (FI->hasFastCall()) {
+      assert(HasFP && "Expecting a valid frame pointer.");
+      if (!isLargeFrame) {
+        BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
+          .addReg(FPReg).addImm(FrameSize);
       } else {
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::LD), PPC::X1)
-           .addImm(0).addReg(PPC::X1);
+        BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
+          .addImm(FrameSize >> 16);
+        BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
+          .addReg(ScratchReg, RegState::Kill)
+          .addImm(FrameSize & 0xFFFF);
+        BuildMI(MBB, MBBI, dl, AddInst)
+          .addReg(SPReg)
+          .addReg(FPReg)
+          .addReg(ScratchReg);
       }
+    } else if (!isLargeFrame && !HasBP && !MFI->hasVarSizedObjects()) {
+      BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
+        .addReg(SPReg)
+        .addImm(FrameSize);
+    } else {
+      BuildMI(MBB, MBBI, dl, LoadInst, SPReg)
+        .addImm(0)
+        .addReg(SPReg);
     }
-  }
-
-  if (isPPC64) {
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LD), PPC::X0)
-        .addImm(LROffset).addReg(PPC::X1);
 
-    if (!MustSaveCRs.empty())
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ8), PPC::X12)
-        .addImm(8).addReg(PPC::X1);
-
-    if (HasFP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LD), PPC::X31)
-        .addImm(FPOffset).addReg(PPC::X1);
+  }
 
-    if (HasBP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LD), PPC::X30)
-        .addImm(BPOffset).addReg(PPC::X1);
+  if (MustSaveLR)
+    BuildMI(MBB, MBBI, dl, LoadInst, ScratchReg)
+      .addImm(LROffset)
+      .addReg(SPReg);
 
-    if (!MustSaveCRs.empty())
-      for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
-        BuildMI(MBB, MBBI, dl, TII.get(PPC::MTOCRF8), MustSaveCRs[i])
-          .addReg(PPC::X12, getKillRegState(i == e-1));
+  assert((isPPC64 || MustSaveCRs.empty()) &&
+         "Epilogue CR restoring supported only in 64-bit mode");
 
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::MTLR8)).addReg(PPC::X0);
-  } else { // PPC32...
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ), PPC::R0)
-          .addImm(LROffset).addReg(PPC::R1);
+  if (!MustSaveCRs.empty()) // will only occur for PPC64
+    BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ8), TempReg)
+      .addImm(8)
+      .addReg(SPReg);
 
-    assert(MustSaveCRs.empty() &&
-           "Epilogue CR restoring supported only in 64-bit mode");
+  if (HasFP)
+    BuildMI(MBB, MBBI, dl, LoadInst, FPReg)
+      .addImm(FPOffset)
+      .addReg(SPReg);
 
-    if (HasFP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ), PPC::R31)
-          .addImm(FPOffset).addReg(PPC::R1);
+  if (HasBP)
+    BuildMI(MBB, MBBI, dl, LoadInst, BPReg)
+      .addImm(BPOffset)
+      .addReg(SPReg);
 
-    if (HasBP)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ), PPC::R30)
-          .addImm(FPOffset).addReg(PPC::R1);
+  if (!MustSaveCRs.empty()) // will only occur for PPC64
+    for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
+      BuildMI(MBB, MBBI, dl, TII.get(PPC::MTOCRF8), MustSaveCRs[i])
+        .addReg(TempReg, getKillRegState(i == e-1));
 
-    if (MustSaveLR)
-      BuildMI(MBB, MBBI, dl, TII.get(PPC::MTLR)).addReg(PPC::R0);
-  }
+  if (MustSaveLR)
+    BuildMI(MBB, MBBI, dl, MTLRInst).addReg(ScratchReg);
 
   // Callee pop calling convention. Pop parameter/linkage area. Used for tail
   // call optimization
@@ -897,27 +827,20 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
       MF.getFunction()->getCallingConv() == CallingConv::Fast) {
      PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
      unsigned CallerAllocatedAmt = FI->getMinReservedArea();
-     unsigned StackReg = isPPC64 ? PPC::X1 : PPC::R1;
-     unsigned FPReg = isPPC64 ? PPC::X31 : PPC::R31;
-     unsigned TmpReg = isPPC64 ? PPC::X0 : PPC::R0;
-     unsigned ADDIInstr = isPPC64 ? PPC::ADDI8 : PPC::ADDI;
-     unsigned ADDInstr = isPPC64 ? PPC::ADD8 : PPC::ADD4;
-     unsigned LISInstr = isPPC64 ? PPC::LIS8 : PPC::LIS;
-     unsigned ORIInstr = isPPC64 ? PPC::ORI8 : PPC::ORI;
 
      if (CallerAllocatedAmt && isInt<16>(CallerAllocatedAmt)) {
-       BuildMI(MBB, MBBI, dl, TII.get(ADDIInstr), StackReg)
-         .addReg(StackReg).addImm(CallerAllocatedAmt);
+       BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
+         .addReg(SPReg).addImm(CallerAllocatedAmt);
      } else {
-       BuildMI(MBB, MBBI, dl, TII.get(LISInstr), TmpReg)
+       BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
           .addImm(CallerAllocatedAmt >> 16);
-       BuildMI(MBB, MBBI, dl, TII.get(ORIInstr), TmpReg)
-          .addReg(TmpReg, RegState::Kill)
+       BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
+          .addReg(ScratchReg, RegState::Kill)
           .addImm(CallerAllocatedAmt & 0xFFFF);
-       BuildMI(MBB, MBBI, dl, TII.get(ADDInstr))
-          .addReg(StackReg)
+       BuildMI(MBB, MBBI, dl, AddInst)
+          .addReg(SPReg)
           .addReg(FPReg)
-          .addReg(TmpReg);
+          .addReg(ScratchReg);
      }
   } else if (RetOpcode == PPC::TCRETURNdi) {
     MBBI = MBB.getLastNonDebugInstr();