TargetJITInfo.h revision bfae83139dcb4fffd50b939e1b1224b0126f04d4 
1//===- Target/TargetJITInfo.h - Target Information for JIT ------*- 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// This file exposes an abstract interface used by the Just-In-Time code
11// generator to perform target-specific activities, such as emitting stubs.  If
12// a TargetMachine supports JIT code generation, it should provide one of these
13// objects through the getJITInfo() method.
14//
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_TARGET_TARGETJITINFO_H
18#define LLVM_TARGET_TARGETJITINFO_H
19
20#include <vector>
21#include <cassert>
22#include "llvm/Support/DataTypes.h"
23
24namespace llvm {
25  class Function;
26  class MachineBasicBlock;
27  class MachineCodeEmitter;
28  class MachineRelocation;
29
30  /// TargetJITInfo - Target specific information required by the Just-In-Time
31  /// code generator.
32  class TargetJITInfo {
33  public:
34    virtual ~TargetJITInfo() {}
35
36    /// replaceMachineCodeForFunction - Make it so that calling the function
37    /// whose machine code is at OLD turns into a call to NEW, perhaps by
38    /// overwriting OLD with a branch to NEW.  This is used for self-modifying
39    /// code.
40    ///
41    virtual void replaceMachineCodeForFunction(void *Old, void *New) = 0;
42
43    /// emitGlobalValueLazyPtr - Use the specified MachineCodeEmitter object to
44    /// emit a lazy pointer which contains the address of the specified GV.
45    virtual void *emitGlobalValueLazyPtr(void *GV, MachineCodeEmitter &MCE) {
46      assert(0 && "This target doesn't implement emitGlobalValueLazyPtr!");
47      return 0;
48    }
49
50    /// emitFunctionStub - Use the specified MachineCodeEmitter object to emit a
51    /// small native function that simply calls the function at the specified
52    /// address.  Return the address of the resultant function.
53    virtual void *emitFunctionStub(void *Fn, MachineCodeEmitter &MCE) {
54      assert(0 && "This target doesn't implement emitFunctionStub!");
55      return 0;
56    }
57
58    /// getPICJumpTableEntry - Returns the value of the jumptable entry for the
59    /// specific basic block.
60    virtual intptr_t getPICJumpTableEntry(intptr_t BB, intptr_t JTBase) {
61      assert(0 && "This target doesn't implement getPICJumpTableEntry!");
62      return 0;
63    }
64
65    /// LazyResolverFn - This typedef is used to represent the function that
66    /// unresolved call points should invoke.  This is a target specific
67    /// function that knows how to walk the stack and find out which stub the
68    /// call is coming from.
69    typedef void (*LazyResolverFn)();
70
71    /// JITCompilerFn - This typedef is used to represent the JIT function that
72    /// lazily compiles the function corresponding to a stub.  The JIT keeps
73    /// track of the mapping between stubs and LLVM Functions, the target
74    /// provides the ability to figure out the address of a stub that is called
75    /// by the LazyResolverFn.
76    typedef void* (*JITCompilerFn)(void *);
77
78    /// getLazyResolverFunction - This method is used to initialize the JIT,
79    /// giving the target the function that should be used to compile a
80    /// function, and giving the JIT the target function used to do the lazy
81    /// resolving.
82    virtual LazyResolverFn getLazyResolverFunction(JITCompilerFn) {
83      assert(0 && "Not implemented for this target!");
84      return 0;
85    }
86
87    /// relocate - Before the JIT can run a block of code that has been emitted,
88    /// it must rewrite the code to contain the actual addresses of any
89    /// referenced global symbols.
90    virtual void relocate(void *Function, MachineRelocation *MR,
91                          unsigned NumRelocs, unsigned char* GOTBase) {
92      assert(NumRelocs == 0 && "This target does not have relocations!");
93    }
94
95    /// needsGOT - Allows a target to specify that it would like the
96    // JIT to manage a GOT for it.
97    bool needsGOT() const { return useGOT; }
98
99  protected:
100    bool useGOT;
101  };
102} // End llvm namespace
103
104#endif
105