1 //===----------- JITSymbol.h - JIT symbol abstraction -----------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Abstraction for target process addresses.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_EXECUTIONENGINE_ORC_JITSYMBOL_H
15 #define LLVM_EXECUTIONENGINE_ORC_JITSYMBOL_H
16 
17 #include "llvm/ExecutionEngine/JITSymbolFlags.h"
18 #include "llvm/Support/DataTypes.h"
19 #include <cassert>
20 #include <functional>
21 
22 namespace llvm {
23 namespace orc {
24 
25 /// @brief Represents an address in the target process's address space.
26 typedef uint64_t TargetAddress;
27 
28 /// @brief Represents a symbol in the JIT.
29 class JITSymbol : public JITSymbolBase {
30 public:
31 
32   typedef std::function<TargetAddress()> GetAddressFtor;
33 
34   /// @brief Create a 'null' symbol that represents failure to find a symbol
35   ///        definition.
JITSymbol(std::nullptr_t)36   JITSymbol(std::nullptr_t)
37       : JITSymbolBase(JITSymbolFlags::None), CachedAddr(0) {}
38 
39   /// @brief Create a symbol for a definition with a known address.
JITSymbol(TargetAddress Addr,JITSymbolFlags Flags)40   JITSymbol(TargetAddress Addr, JITSymbolFlags Flags)
41     : JITSymbolBase(Flags), CachedAddr(Addr) {}
42 
43   /// @brief Create a symbol for a definition that doesn't have a known address
44   ///        yet.
45   /// @param GetAddress A functor to materialize a definition (fixing the
46   ///        address) on demand.
47   ///
48   ///   This constructor allows a JIT layer to provide a reference to a symbol
49   /// definition without actually materializing the definition up front. The
50   /// user can materialize the definition at any time by calling the getAddress
51   /// method.
JITSymbol(GetAddressFtor GetAddress,JITSymbolFlags Flags)52   JITSymbol(GetAddressFtor GetAddress, JITSymbolFlags Flags)
53       : JITSymbolBase(Flags), GetAddress(std::move(GetAddress)), CachedAddr(0) {}
54 
55   /// @brief Returns true if the symbol exists, false otherwise.
56   explicit operator bool() const { return CachedAddr || GetAddress; }
57 
58   /// @brief Get the address of the symbol in the target address space. Returns
59   ///        '0' if the symbol does not exist.
getAddress()60   TargetAddress getAddress() {
61     if (GetAddress) {
62       CachedAddr = GetAddress();
63       assert(CachedAddr && "Symbol could not be materialized.");
64       GetAddress = nullptr;
65     }
66     return CachedAddr;
67   }
68 
69 private:
70   GetAddressFtor GetAddress;
71   TargetAddress CachedAddr;
72 };
73 
74 } // End namespace orc.
75 } // End namespace llvm.
76 
77 #endif // LLVM_EXECUTIONENGINE_ORC_JITSYMBOL_H
78