1//===---- TargetInfo.h - Encapsulate target details -------------*- 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// These classes wrap the information about a call or function
11// definition used to handle ABI compliancy.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef CLANG_CODEGEN_TARGETINFO_H
16#define CLANG_CODEGEN_TARGETINFO_H
17
18#include "clang/Basic/LLVM.h"
19#include "clang/AST/Type.h"
20#include "llvm/ADT/StringRef.h"
21
22namespace llvm {
23  class GlobalValue;
24  class Type;
25  class Value;
26}
27
28namespace clang {
29  class ABIInfo;
30  class Decl;
31
32  namespace CodeGen {
33    class CallArgList;
34    class CodeGenModule;
35    class CodeGenFunction;
36    class CGFunctionInfo;
37  }
38
39  /// TargetCodeGenInfo - This class organizes various target-specific
40  /// codegeneration issues, like target-specific attributes, builtins and so
41  /// on.
42  class TargetCodeGenInfo {
43    ABIInfo *Info;
44  public:
45    // WARNING: Acquires the ownership of ABIInfo.
46    TargetCodeGenInfo(ABIInfo *info = 0):Info(info) { }
47    virtual ~TargetCodeGenInfo();
48
49    /// getABIInfo() - Returns ABI info helper for the target.
50    const ABIInfo& getABIInfo() const { return *Info; }
51
52    /// SetTargetAttributes - Provides a convenient hook to handle extra
53    /// target-specific attributes for the given global.
54    virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
55                                     CodeGen::CodeGenModule &M) const { }
56
57    /// Determines the size of struct _Unwind_Exception on this platform,
58    /// in 8-bit units.  The Itanium ABI defines this as:
59    ///   struct _Unwind_Exception {
60    ///     uint64 exception_class;
61    ///     _Unwind_Exception_Cleanup_Fn exception_cleanup;
62    ///     uint64 private_1;
63    ///     uint64 private_2;
64    ///   };
65    virtual unsigned getSizeOfUnwindException() const;
66
67    /// Controls whether __builtin_extend_pointer should sign-extend
68    /// pointers to uint64_t or zero-extend them (the default).  Has
69    /// no effect for targets:
70    ///   - that have 64-bit pointers, or
71    ///   - that cannot address through registers larger than pointers, or
72    ///   - that implicitly ignore/truncate the top bits when addressing
73    ///     through such registers.
74    virtual bool extendPointerWithSExt() const { return false; }
75
76    /// Determines the DWARF register number for the stack pointer, for
77    /// exception-handling purposes.  Implements __builtin_dwarf_sp_column.
78    ///
79    /// Returns -1 if the operation is unsupported by this target.
80    virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
81      return -1;
82    }
83
84    /// Initializes the given DWARF EH register-size table, a char*.
85    /// Implements __builtin_init_dwarf_reg_size_table.
86    ///
87    /// Returns true if the operation is unsupported by this target.
88    virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
89                                         llvm::Value *Address) const {
90      return true;
91    }
92
93    /// Performs the code-generation required to convert a return
94    /// address as stored by the system into the actual address of the
95    /// next instruction that will be executed.
96    ///
97    /// Used by __builtin_extract_return_addr().
98    virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
99                                             llvm::Value *Address) const {
100      return Address;
101    }
102
103    /// Performs the code-generation required to convert the address
104    /// of an instruction into a return address suitable for storage
105    /// by the system in a return slot.
106    ///
107    /// Used by __builtin_frob_return_addr().
108    virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
109                                             llvm::Value *Address) const {
110      return Address;
111    }
112
113    virtual llvm::Type* adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
114                                            StringRef Constraint,
115                                            llvm::Type* Ty) const {
116      return Ty;
117    }
118
119    /// Retrieve the address of a function to call immediately before
120    /// calling objc_retainAutoreleasedReturnValue.  The
121    /// implementation of objc_autoreleaseReturnValue sniffs the
122    /// instruction stream following its return address to decide
123    /// whether it's a call to objc_retainAutoreleasedReturnValue.
124    /// This can be prohibitively expensive, depending on the
125    /// relocation model, and so on some targets it instead sniffs for
126    /// a particular instruction sequence.  This functions returns
127    /// that instruction sequence in inline assembly, which will be
128    /// empty if none is required.
129    virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
130      return "";
131    }
132
133    /// Determine whether a call to an unprototyped functions under
134    /// the given calling convention should use the variadic
135    /// convention or the non-variadic convention.
136    ///
137    /// There's a good reason to make a platform's variadic calling
138    /// convention be different from its non-variadic calling
139    /// convention: the non-variadic arguments can be passed in
140    /// registers (better for performance), and the variadic arguments
141    /// can be passed on the stack (also better for performance).  If
142    /// this is done, however, unprototyped functions *must* use the
143    /// non-variadic convention, because C99 states that a call
144    /// through an unprototyped function type must succeed if the
145    /// function was defined with a non-variadic prototype with
146    /// compatible parameters.  Therefore, splitting the conventions
147    /// makes it impossible to call a variadic function through an
148    /// unprototyped type.  Since function prototypes came out in the
149    /// late 1970s, this is probably an acceptable trade-off.
150    /// Nonetheless, not all platforms are willing to make it, and in
151    /// particularly x86-64 bends over backwards to make the
152    /// conventions compatible.
153    ///
154    /// The default is false.  This is correct whenever:
155    ///   - the conventions are exactly the same, because it does not
156    ///     matter and the resulting IR will be somewhat prettier in
157    ///     certain cases; or
158    ///   - the conventions are substantively different in how they pass
159    ///     arguments, because in this case using the variadic convention
160    ///     will lead to C99 violations.
161    /// It is not necessarily correct when arguments are passed in the
162    /// same way and some out-of-band information is passed for the
163    /// benefit of variadic callees, as is the case for x86-64.
164    /// In this case the ABI should be consulted.
165    virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
166                                       const FunctionNoProtoType *fnType) const;
167  };
168}
169
170#endif // CLANG_CODEGEN_TARGETINFO_H
171