TargetJITInfo.h revision 55b5053b8e22cf165d1f0ce3aa9a04707e368a15 
1//===- Target/TargetJITInfo.h - Target Information for JIT ------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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 <cassert>
21#include <vector>
22
23namespace llvm {
24  class Function;
25  class FunctionPassManager;
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    /// addPassesToJITCompile - Add passes to the specified pass manager to
37    /// implement a fast code generator for this target.
38    ///
39    virtual void addPassesToJITCompile(FunctionPassManager &PM) = 0;
40
41    /// replaceMachineCodeForFunction - Make it so that calling the function
42    /// whose machine code is at OLD turns into a call to NEW, perhaps by
43    /// overwriting OLD with a branch to NEW.  This is used for self-modifying
44    /// code.
45    ///
46    virtual void replaceMachineCodeForFunction(void *Old, void *New) = 0;
47
48    /// emitFunctionStub - Use the specified MachineCodeEmitter object to emit a
49    /// small native function that simply calls the function at the specified
50    /// address.  Return the address of the resultant function.
51    virtual void *emitFunctionStub(void *Fn, MachineCodeEmitter &MCE) {
52      assert(0 && "This target doesn't implement emitFunctionStub!");
53      return 0;
54    }
55
56    /// LazyResolverFn - This typedef is used to represent the function that
57    /// unresolved call points should invoke.  This is a target specific
58    /// function that knows how to walk the stack and find out which stub the
59    /// call is coming from.
60    typedef void (*LazyResolverFn)();
61
62    /// JITCompilerFn - This typedef is used to represent the JIT function that
63    /// lazily compiles the function corresponding to a stub.  The JIT keeps
64    /// track of the mapping between stubs and LLVM Functions, the target
65    /// provides the ability to figure out the address of a stub that is called
66    /// by the LazyResolverFn.
67    typedef void* (*JITCompilerFn)(void *);
68
69    /// getLazyResolverFunction - This method is used to initialize the JIT,
70    /// giving the target the function that should be used to compile a
71    /// function, and giving the JIT the target function used to do the lazy
72    /// resolving.
73    virtual LazyResolverFn getLazyResolverFunction(JITCompilerFn) {
74      assert(0 && "Not implemented for this target!");
75      return 0;
76    }
77
78    /// relocate - Before the JIT can run a block of code that has been emitted,
79    /// it must rewrite the code to contain the actual addresses of any
80    /// referenced global symbols.
81    virtual void relocate(void *Function, MachineRelocation *MR,
82                          unsigned NumRelocs, unsigned char* GOTBase) {
83      assert(NumRelocs == 0 && "This target does not have relocations!");
84    }
85
86    /// resolveBBRefs - Resolve branches to BasicBlocks for the JIT emitted
87    /// function.
88    virtual void resolveBBRefs(MachineCodeEmitter &MCE) {}
89
90    /// addBBRef - Add a BasicBlock reference to be resolved after the function
91    /// is emitted.
92    void addBBRef(MachineBasicBlock *BB, intptr_t PC) {
93      BBRefs.push_back(std::make_pair(BB, PC));
94    }
95
96    /// needsGOT - Allows a target to specify that it would like the
97    // JIT to manage a GOT for it.
98    bool needsGOT() const { return useGOT; }
99
100  protected:
101    bool useGOT;
102
103    // Tracks which instruction references which BasicBlock
104    std::vector<std::pair<MachineBasicBlock*, intptr_t> > BBRefs;
105
106  };
107} // End llvm namespace
108
109#endif
110