[AArch64][DebugInfo]Add Target hooks for InstrRef on AArch64

According to llvm/docs/InstrRefDebugInfo.md, to support proper
instruction referecing on any platform, the target specific
`TargetInstrInfo::isLoadFromStackSlotPostFE` and
`TargetInstrInfo::isStoreToStackSlotPostFE` functions are needed to be
implemented for the Instruction Reference-based LiveDebugValues pass to
identify spill and restore instructions.

This patch is attempting to reland
llvm#162327

Author: rastogishubham

llvm/lib/Target/AArch64/AArch64InstrInfo.cpp

@@ -2440,11 +2440,10 @@ bool AArch64InstrInfo::isFPRCopy(const MachineInstr &MI) {
   return false;
 }
 
-Register AArch64InstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
-                                               int &FrameIndex) const {
-  switch (MI.getOpcode()) {
+static bool isFrameLoadOpcode(int Opcode) {
+  switch (Opcode) {
   default:
-    break;
+    return false;
   case AArch64::LDRWui:
   case AArch64::LDRXui:
   case AArch64::LDRBui:
@@ -2453,22 +2452,27 @@ Register AArch64InstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
   case AArch64::LDRDui:
   case AArch64::LDRQui:
   case AArch64::LDR_PXI:
-    if (MI.getOperand(0).getSubReg() == 0 && MI.getOperand(1).isFI() &&
-        MI.getOperand(2).isImm() && MI.getOperand(2).getImm() == 0) {
-      FrameIndex = MI.getOperand(1).getIndex();
-      return MI.getOperand(0).getReg();
-    }
-    break;
+    return true;
   }
+}
+
+Register AArch64InstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
+                                               int &FrameIndex) const {
+  if (!isFrameLoadOpcode(MI.getOpcode()))
+    return Register();
 
-  return 0;
+  if (MI.getOperand(0).getSubReg() == 0 && MI.getOperand(1).isFI() &&
+      MI.getOperand(2).isImm() && MI.getOperand(2).getImm() == 0) {
+    FrameIndex = MI.getOperand(1).getIndex();
+    return MI.getOperand(0).getReg();
+  }
+  return Register();
 }
 
-Register AArch64InstrInfo::isStoreToStackSlot(const MachineInstr &MI,
-                                              int &FrameIndex) const {
-  switch (MI.getOpcode()) {
+static bool isFrameStoreOpcode(int Opcode) {
+  switch (Opcode) {
   default:
-    break;
+    return false;
   case AArch64::STRWui:
   case AArch64::STRXui:
   case AArch64::STRBui:
@@ -2477,14 +2481,57 @@ Register AArch64InstrInfo::isStoreToStackSlot(const MachineInstr &MI,
   case AArch64::STRDui:
   case AArch64::STRQui:
   case AArch64::STR_PXI:
-    if (MI.getOperand(0).getSubReg() == 0 && MI.getOperand(1).isFI() &&
-        MI.getOperand(2).isImm() && MI.getOperand(2).getImm() == 0) {
-      FrameIndex = MI.getOperand(1).getIndex();
-      return MI.getOperand(0).getReg();
-    }
-    break;
+    return true;
   }
-  return 0;
+}
+
+Register AArch64InstrInfo::isStoreToStackSlot(const MachineInstr &MI,
+                                              int &FrameIndex) const {
+  if (!isFrameStoreOpcode(MI.getOpcode()))
+    return Register();
+
+  if (MI.getOperand(0).getSubReg() == 0 && MI.getOperand(1).isFI() &&
+      MI.getOperand(2).isImm() && MI.getOperand(2).getImm() == 0) {
+    FrameIndex = MI.getOperand(1).getIndex();
+    return MI.getOperand(0).getReg();
+  }
+  return Register();
+}
+
+Register AArch64InstrInfo::isStoreToStackSlotPostFE(const MachineInstr &MI,
+                                                    int &FrameIndex) const {
+  if (!isFrameStoreOpcode(MI.getOpcode()))
+    return Register();
+
+  if (Register Reg = isStoreToStackSlot(MI, FrameIndex))
+    return Reg;
+
+  SmallVector<const MachineMemOperand *, 1> Accesses;
+  if (hasStoreToStackSlot(MI, Accesses)) {
+    FrameIndex =
+        cast<FixedStackPseudoSourceValue>(Accesses.front()->getPseudoValue())
+            ->getFrameIndex();
+    return MI.getOperand(0).getReg();
+  }
+  return Register();
+}
+
+Register AArch64InstrInfo::isLoadFromStackSlotPostFE(const MachineInstr &MI,
+                                                     int &FrameIndex) const {
+  if (!isFrameLoadOpcode(MI.getOpcode()))
+    return Register();
+
+  if (Register Reg = isLoadFromStackSlot(MI, FrameIndex))
+    return Reg;
+
+  SmallVector<const MachineMemOperand *, 1> Accesses;
+  if (hasLoadFromStackSlot(MI, Accesses)) {
+    FrameIndex =
+        cast<FixedStackPseudoSourceValue>(Accesses.front()->getPseudoValue())
+            ->getFrameIndex();
+    return MI.getOperand(0).getReg();
+  }
+  return Register();
 }
 
 /// Check all MachineMemOperands for a hint to suppress pairing.

llvm/lib/Target/AArch64/AArch64InstrInfo.h

@@ -205,6 +205,15 @@ class AArch64InstrInfo final : public AArch64GenInstrInfo {
   Register isStoreToStackSlot(const MachineInstr &MI,
                               int &FrameIndex) const override;
 
+  /// Check for post-frame ptr elimination stack locations as well.  This uses a
+  /// heuristic so it isn't reliable for correctness.
+  Register isStoreToStackSlotPostFE(const MachineInstr &MI,
+                                    int &FrameIndex) const override;
+  /// Check for post-frame ptr elimination stack locations as well.  This uses a
+  /// heuristic so it isn't reliable for correctness.
+  Register isLoadFromStackSlotPostFE(const MachineInstr &MI,
+                                     int &FrameIndex) const override;
+
   /// Does this instruction set its full destination register to zero?
   static bool isGPRZero(const MachineInstr &MI);