[llvm] [Xtensa] Implement base CallConvention. (PR #83280)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,264 @@
+//===- XtensaConstantPoolValue.h - Xtensa constantpool value ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Xtensa specific constantpool value class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_XTENSA_XTENSACONSTANTPOOLVALUE_H
+#define LLVM_LIB_TARGET_XTENSA_XTENSACONSTANTPOOLVALUE_H
+
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <cstddef>
+#include <string>
+#include <vector>
+
+namespace llvm {
+
+class BlockAddress;
+class Constant;
+class GlobalValue;
+class LLVMContext;
+class MachineBasicBlock;
+
+namespace XtensaCP {
+enum XtensaCPKind {
+  CPExtSymbol,
+  CPBlockAddress,
+  CPMachineBasicBlock,
+  CPJumpTable
+};
+
+enum XtensaCPModifier {
+  no_modifier, // None
+  TPOFF        // Thread Pointer Offset
+};
+} // namespace XtensaCP
+
+/// XtensaConstantPoolValue - Xtensa specific constantpool value. This is used
+/// to represent PC-relative displacement between the address of the load
+/// instruction and the constant being loaded.
+class XtensaConstantPoolValue : public MachineConstantPoolValue {
+  unsigned LabelId;                    // Label id of the load.
+  XtensaCP::XtensaCPKind Kind;         // Kind of constant.
+  XtensaCP::XtensaCPModifier Modifier; // Symbol name modifier
+                                       //(for example Global Variable name)
+
+protected:
+  XtensaConstantPoolValue(
+      Type *Ty, unsigned id, XtensaCP::XtensaCPKind Kind,
+      XtensaCP::XtensaCPModifier Modifier = XtensaCP::no_modifier);
+
+  XtensaConstantPoolValue(
+      LLVMContext &C, unsigned id, XtensaCP::XtensaCPKind Kind,
+      XtensaCP::XtensaCPModifier Modifier = XtensaCP::no_modifier);
+
+  template <typename Derived>
+  int getExistingMachineCPValueImpl(MachineConstantPool *CP, Align Alignment) {
+    const std::vector<MachineConstantPoolEntry> &Constants = CP->getConstants();
+    for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
+      if (Constants[i].isMachineConstantPoolEntry() &&
+          (Constants[i].getAlign() >= Alignment)) {
+        XtensaConstantPoolValue *CPV =
+            (XtensaConstantPoolValue *)Constants[i].Val.MachineCPVal;
+        if (Derived *APC = dyn_cast<Derived>(CPV))
+          if (cast<Derived>(this)->equals(APC))
+            return i;
+      }
+    }
+
+    return -1;
+  }
+
+public:
+  ~XtensaConstantPoolValue() override;
+
+  XtensaCP::XtensaCPModifier getModifier() const { return Modifier; }
+  bool hasModifier() const { return Modifier != XtensaCP::no_modifier; }
+  StringRef getModifierText() const;
+
+  unsigned getLabelId() const { return LabelId; }
+  void setLabelId(unsigned id) { LabelId = id; }
+
+  bool isExtSymbol() const { return Kind == XtensaCP::CPExtSymbol; }
+  bool isBlockAddress() const { return Kind == XtensaCP::CPBlockAddress; }
+  bool isMachineBasicBlock() const {
+    return Kind == XtensaCP::CPMachineBasicBlock;
+  }
+  bool isJumpTable() const { return Kind == XtensaCP::CPJumpTable; }
+
+  int getExistingMachineCPValue(MachineConstantPool *CP,
+                                Align Alignment) override;
+
+  void addSelectionDAGCSEId(FoldingSetNodeID &ID) override;
+
+  /// hasSameValue - Return true if this Xtensa constpool value can share the
+  /// same constantpool entry as another Xtensa constpool value.
+  virtual bool hasSameValue(XtensaConstantPoolValue *ACPV);
+
+  bool equals(const XtensaConstantPoolValue *A) const {
+    return this->LabelId == A->LabelId && this->Modifier == A->Modifier;
+  }
+
+  void print(raw_ostream &O) const override;
+  void print(raw_ostream *O) const {
+    if (O)
+      print(*O);
+  }
----------------
arsenm wrote:

This shouldn't be necessary? 

https://github.com/llvm/llvm-project/pull/83280