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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18029 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineRelocation.h

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+//===-- llvm/CodeGen/MachineRelocation.h - Target Relocation ----*- C++ -*-===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file defines the MachineRelocation class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINERELOCATION_H
+#define LLVM_CODEGEN_MACHINERELOCATION_H
+
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+class GlobalValue;
+
+/// MachineRelocation - This represents a target-specific relocation value,
+/// produced by the code emitter.  This relocation is resolved after the has
+/// been emitted, either to an object file or to memory, when the target of the
+/// relocation can be resolved.
+///
+/// A relocation is made up of the following logical portions:
+///   1. An offset in the machine code buffer, the location to modify.
+///   2. A target specific relocation type (a number from 0 to 127).
+///   3. A symbol being referenced, either as a GlobalValue* or as a string.
+///   4. An optional constant value to be added to the reference.
+///
+class MachineRelocation {
+  /// OffsetTypeExternal - The low 24-bits of this value is the offset from the
+  /// start of the code buffer of the relocation to perform.  Bit 24 of this is
+  /// set if Target should use ExtSym instead of GV, and the high 7 bits are to
+  /// hold the relocation type.
+  unsigned OffsetTypeExternal;
+  union {
+    GlobalValue *GV;     // If this is a pointer to an LLVM global
+    const char *ExtSym;  // If this is a pointer to a named symbol
+    void *Result;        // If this has been resolved to a resolved pointer
+  } Target;
+  intptr_t ConstantVal;
+public:
+  MachineRelocation(unsigned Offset, unsigned RelocationType, GlobalValue *GV,
+             intptr_t cst = 0)
+    : OffsetTypeExternal(Offset + (RelocationType << 25)), ConstantVal(cst) {
+    assert((Offset & ~((1 << 24)-1)) == 0 && "Code offset too large!");
+    assert((RelocationType & ~127) == 0 && "Relocation type too large!");
+    Target.GV = GV;
+  }
+
+  MachineRelocation(unsigned Offset, unsigned RelocationType, const char *ES,
+             intptr_t cst = 0)
+    : OffsetTypeExternal(Offset + (1 << 24) + (RelocationType << 25)),
+    ConstantVal(cst) {
+    assert((Offset & ~((1 << 24)-1)) == 0 && "Code offset too large!");
+    assert((RelocationType & ~127) == 0 && "Relocation type too large!");
+    Target.ExtSym = ES;
+  }
+
+  /// getMachineCodeOffset - Return the offset into the code buffer that the
+  /// relocation should be performed.
+  unsigned getMachineCodeOffset() const {
+    return OffsetTypeExternal & ((1 << 24)-1);
+  }
+
+  /// getConstantVal - Get the constant value associated with this relocation.
+  /// This is often an offset from the symbol.
+  ///
+  intptr_t getConstantVal() const {
+    return ConstantVal;
+  }
+
+  /// isGlobalValue - Return true if this relocation is a GlobalValue, as
+  /// opposed to a constant string.
+  bool isGlobalValue() const {
+    return (OffsetTypeExternal & (1 << 24)) == 0;
+  }
+
+  /// isString - Return true if this is a constant string.
+  ///
+  bool isString() const {
+    return !isGlobalValue();
+  }
+
+  /// getGlobalValue - If this is a global value reference, return the
+  /// referenced global.
+  GlobalValue *getGlobalValue() const {
+    assert(isGlobalValue() && "This is not a global value reference!");
+    return Target.GV;
+  }
+
+  /// getString - If this is a string value, return the string reference.
+  ///
+  const char *getString() const {
+    assert(isString() && "This is not a string reference!");
+    return Target.ExtSym;
+  }
+
+  /// getResultPointer - Once this has been resolved to point to an actual
+  /// address, this returns the pointer.
+  void *getResultPointer() const {
+    return Target.Result;
+  }
+
+  /// setResultPointer - Set the result to the specified pointer value.
+  ///
+  void setResultPointer(void *Ptr) {
+    Target.Result = Ptr;
+  }
+};
+
+}
+
+#endif