Factor out resolveFrameOffsetReference.

[eugenis]

Summary

Split AArch64FrameLowering::resolveFrameIndexReference in two parts

• Finding frame offset for the index.
• Finding base register and offset to that register.

The second part will be used to implement a virtual frame pointer in
armv8.5 MTE stack instrumentation lowering.

[ostannard]

LGTM

llvm/trunk/lib/Target/AArch64/AArch64FrameLowering.h

public:
 
   bool canUseAsPrologue(const MachineBasicBlock &MBB) const override;
 
   int getFrameIndexReference(const MachineFunction &MF, int FI,
                              unsigned &FrameReg) const override;
   int resolveFrameIndexReference(const MachineFunction &MF, int FI,
                                  unsigned &FrameReg, bool PreferFP,
                                  bool ForSimm) const;
+  int resolveFrameOffsetReference(const MachineFunction &MF, int ObjectOffset,
+                                  bool isFixed, unsigned &FrameReg,
+                                  bool PreferFP, bool ForSimm) const;
   bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
                                  MachineBasicBlock::iterator MI,
                                  const std::vector<CalleeSavedInfo> &CSI,
                                  const TargetRegisterInfo *TRI) const override;
 
   bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MI,
                                   std::vector<CalleeSavedInfo> &CSI,

llvm/trunk/lib/Target/AArch64/AArch64FrameLowering.cpp

return resolveFrameIndexReference(
       /*ForSimm=*/false);
 }
 
 int AArch64FrameLowering::getNonLocalFrameIndexReference(
   const MachineFunction &MF, int FI) const {
   return getSEHFrameIndexOffset(MF, FI);
 }
 
-static int getFPOffset(const MachineFunction &MF, int FI) {
-  const auto &MFI = MF.getFrameInfo();
+static int getFPOffset(const MachineFunction &MF, int ObjectOffset) {
   const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
   const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
   unsigned FixedObject = IsWin64 ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
-  return MFI.getObjectOffset(FI) + FixedObject + 16;
+  return ObjectOffset + FixedObject + 16;
 }
 
-static int getStackOffset(const MachineFunction &MF, int FI) {
+static int getStackOffset(const MachineFunction &MF, int ObjectOffset) {
   const auto &MFI = MF.getFrameInfo();
-  return MFI.getObjectOffset(FI) + MFI.getStackSize();
+  return ObjectOffset + MFI.getStackSize();
 }
 
 int AArch64FrameLowering::getSEHFrameIndexOffset(const MachineFunction &MF,
                                                  int FI) const {
   const auto *RegInfo = static_cast<const AArch64RegisterInfo *>(
       MF.getSubtarget().getRegisterInfo());
-  return RegInfo->getLocalAddressRegister(MF) == AArch64::FP ?
-         getFPOffset(MF, FI) : getStackOffset(MF, FI);
+  int ObjectOffset = MF.getFrameInfo().getObjectOffset(FI);
+  return RegInfo->getLocalAddressRegister(MF) == AArch64::FP
+             ? getFPOffset(MF, ObjectOffset)
+             : getStackOffset(MF, ObjectOffset);
 }
 
 int AArch64FrameLowering::resolveFrameIndexReference(const MachineFunction &MF,
                                                      int FI, unsigned &FrameReg,
                                                      bool PreferFP,
                                                      bool ForSimm) const {
   const auto &MFI = MF.getFrameInfo();
+  int ObjectOffset = MFI.getObjectOffset(FI);
+  bool isFixed = MFI.isFixedObjectIndex(FI);
+  return resolveFrameOffsetReference(MF, ObjectOffset, isFixed, FrameReg,
+                                     PreferFP, ForSimm);
+}
+
+int AArch64FrameLowering::resolveFrameOffsetReference(
+    const MachineFunction &MF, int ObjectOffset, bool isFixed,
+    unsigned &FrameReg, bool PreferFP, bool ForSimm) const {
+  const auto &MFI = MF.getFrameInfo();
   const auto *RegInfo = static_cast<const AArch64RegisterInfo *>(
       MF.getSubtarget().getRegisterInfo());
   const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
   const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
-  int FPOffset = getFPOffset(MF, FI);
-  int Offset = getStackOffset(MF, FI);
-  bool isFixed = MFI.isFixedObjectIndex(FI);
-  bool isCSR = !isFixed && MFI.getObjectOffset(FI) >=
-                               -((int)AFI->getCalleeSavedStackSize());
+
+  int FPOffset = getFPOffset(MF, ObjectOffset);
+  int Offset = getStackOffset(MF, ObjectOffset);
+  bool isCSR =
+      !isFixed && ObjectOffset >= -((int)AFI->getCalleeSavedStackSize());
 
   // Use frame pointer to reference fixed objects. Use it for locals if
   // there are VLAs or a dynamically realigned SP (and thus the SP isn't
   // reliable as a base). Make sure useFPForScavengingIndex() does the
   // right thing for the emergency spill slot.
   bool UseFP = false;
   if (AFI->hasStackFrame()) {
     // Note: Keeping the following as multiple 'if' statements rather than