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 <cassert>
21#include "llvm/Support/ErrorHandling.h"
22#include "llvm/Support/DataTypes.h"
23
24namespace llvm {
25  class Function;
26  class GlobalValue;
27  class JITCodeEmitter;
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    /// emitGlobalValueIndirectSym - Use the specified JITCodeEmitter object
44    /// to emit an indirect symbol which contains the address of the specified
45    /// ptr.
46    virtual void *emitGlobalValueIndirectSym(const GlobalValue* GV, void *ptr,
47                                             JITCodeEmitter &JCE) {
48      assert(0 && "This target doesn't implement emitGlobalValueIndirectSym!");
49      return 0;
50    }
51
52    /// Records the required size and alignment for a call stub in bytes.
53    struct StubLayout {
54      size_t Size;
55      size_t Alignment;
56    };
57    /// Returns the maximum size and alignment for a call stub on this target.
58    virtual StubLayout getStubLayout() {
59      llvm_unreachable("This target doesn't implement getStubLayout!");
60      StubLayout Result = {0, 0};
61      return Result;
62    }
63
64    /// emitFunctionStub - Use the specified JITCodeEmitter object to emit a
65    /// small native function that simply calls the function at the specified
66    /// address.  The JITCodeEmitter must already have storage allocated for the
67    /// stub.  Return the address of the resultant function, which may have been
68    /// aligned from the address the JCE was set up to emit at.
69    virtual void *emitFunctionStub(const Function* F, void *Target,
70                                   JITCodeEmitter &JCE) {
71      assert(0 && "This target doesn't implement emitFunctionStub!");
72      return 0;
73    }
74
75    /// getPICJumpTableEntry - Returns the value of the jumptable entry for the
76    /// specific basic block.
77    virtual uintptr_t getPICJumpTableEntry(uintptr_t BB, uintptr_t JTBase) {
78      assert(0 && "This target doesn't implement getPICJumpTableEntry!");
79      return 0;
80    }
81
82    /// LazyResolverFn - This typedef is used to represent the function that
83    /// unresolved call points should invoke.  This is a target specific
84    /// function that knows how to walk the stack and find out which stub the
85    /// call is coming from.
86    typedef void (*LazyResolverFn)();
87
88    /// JITCompilerFn - This typedef is used to represent the JIT function that
89    /// lazily compiles the function corresponding to a stub.  The JIT keeps
90    /// track of the mapping between stubs and LLVM Functions, the target
91    /// provides the ability to figure out the address of a stub that is called
92    /// by the LazyResolverFn.
93    typedef void* (*JITCompilerFn)(void *);
94
95    /// getLazyResolverFunction - This method is used to initialize the JIT,
96    /// giving the target the function that should be used to compile a
97    /// function, and giving the JIT the target function used to do the lazy
98    /// resolving.
99    virtual LazyResolverFn getLazyResolverFunction(JITCompilerFn) {
100      assert(0 && "Not implemented for this target!");
101      return 0;
102    }
103
104    /// relocate - Before the JIT can run a block of code that has been emitted,
105    /// it must rewrite the code to contain the actual addresses of any
106    /// referenced global symbols.
107    virtual void relocate(void *Function, MachineRelocation *MR,
108                          unsigned NumRelocs, unsigned char* GOTBase) {
109      assert(NumRelocs == 0 && "This target does not have relocations!");
110    }
111
112
113    /// allocateThreadLocalMemory - Each target has its own way of
114    /// handling thread local variables. This method returns a value only
115    /// meaningful to the target.
116    virtual char* allocateThreadLocalMemory(size_t size) {
117      assert(0 && "This target does not implement thread local storage!");
118      return 0;
119    }
120
121    /// needsGOT - Allows a target to specify that it would like the
122    /// JIT to manage a GOT for it.
123    bool needsGOT() const { return useGOT; }
124
125    /// hasCustomConstantPool - Allows a target to specify that constant
126    /// pool address resolution is handled by the target.
127    virtual bool hasCustomConstantPool() const { return false; }
128
129    /// hasCustomJumpTables - Allows a target to specify that jumptables
130    /// are emitted by the target.
131    virtual bool hasCustomJumpTables() const { return false; }
132
133    /// allocateSeparateGVMemory - If true, globals should be placed in
134    /// separately allocated heap memory rather than in the same
135    /// code memory allocated by JITCodeEmitter.
136    virtual bool allocateSeparateGVMemory() const { return false; }
137  protected:
138    bool useGOT;
139  };
140} // End llvm namespace
141
142#endif
143