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/AST/Type.h"
19#include "clang/Basic/LLVM.h"
20#include "llvm/ADT/StringRef.h"
21#include "llvm/ADT/SmallString.h"
22
23namespace llvm {
24  class Constant;
25  class GlobalValue;
26  class Type;
27  class Value;
28}
29
30namespace clang {
31  class ABIInfo;
32  class Decl;
33
34  namespace CodeGen {
35    class CallArgList;
36    class CodeGenModule;
37    class CodeGenFunction;
38    class CGFunctionInfo;
39  }
40
41  /// TargetCodeGenInfo - This class organizes various target-specific
42  /// codegeneration issues, like target-specific attributes, builtins and so
43  /// on.
44  class TargetCodeGenInfo {
45    ABIInfo *Info;
46  public:
47    // WARNING: Acquires the ownership of ABIInfo.
48    TargetCodeGenInfo(ABIInfo *info = 0):Info(info) { }
49    virtual ~TargetCodeGenInfo();
50
51    /// getABIInfo() - Returns ABI info helper for the target.
52    const ABIInfo& getABIInfo() const { return *Info; }
53
54    /// SetTargetAttributes - Provides a convenient hook to handle extra
55    /// target-specific attributes for the given global.
56    virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
57                                     CodeGen::CodeGenModule &M) const { }
58
59    /// Determines the size of struct _Unwind_Exception on this platform,
60    /// in 8-bit units.  The Itanium ABI defines this as:
61    ///   struct _Unwind_Exception {
62    ///     uint64 exception_class;
63    ///     _Unwind_Exception_Cleanup_Fn exception_cleanup;
64    ///     uint64 private_1;
65    ///     uint64 private_2;
66    ///   };
67    virtual unsigned getSizeOfUnwindException() const;
68
69    /// Controls whether __builtin_extend_pointer should sign-extend
70    /// pointers to uint64_t or zero-extend them (the default).  Has
71    /// no effect for targets:
72    ///   - that have 64-bit pointers, or
73    ///   - that cannot address through registers larger than pointers, or
74    ///   - that implicitly ignore/truncate the top bits when addressing
75    ///     through such registers.
76    virtual bool extendPointerWithSExt() const { return false; }
77
78    /// Determines the DWARF register number for the stack pointer, for
79    /// exception-handling purposes.  Implements __builtin_dwarf_sp_column.
80    ///
81    /// Returns -1 if the operation is unsupported by this target.
82    virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
83      return -1;
84    }
85
86    /// Initializes the given DWARF EH register-size table, a char*.
87    /// Implements __builtin_init_dwarf_reg_size_table.
88    ///
89    /// Returns true if the operation is unsupported by this target.
90    virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
91                                         llvm::Value *Address) const {
92      return true;
93    }
94
95    /// Performs the code-generation required to convert a return
96    /// address as stored by the system into the actual address of the
97    /// next instruction that will be executed.
98    ///
99    /// Used by __builtin_extract_return_addr().
100    virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
101                                             llvm::Value *Address) const {
102      return Address;
103    }
104
105    /// Performs the code-generation required to convert the address
106    /// of an instruction into a return address suitable for storage
107    /// by the system in a return slot.
108    ///
109    /// Used by __builtin_frob_return_addr().
110    virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
111                                             llvm::Value *Address) const {
112      return Address;
113    }
114
115    /// Corrects the low-level LLVM type for a given constraint and "usual"
116    /// type.
117    ///
118    /// \returns A pointer to a new LLVM type, possibly the same as the original
119    /// on success; 0 on failure.
120    virtual llvm::Type* adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
121                                            StringRef Constraint,
122                                            llvm::Type* Ty) const {
123      return Ty;
124    }
125
126    /// Retrieve the address of a function to call immediately before
127    /// calling objc_retainAutoreleasedReturnValue.  The
128    /// implementation of objc_autoreleaseReturnValue sniffs the
129    /// instruction stream following its return address to decide
130    /// whether it's a call to objc_retainAutoreleasedReturnValue.
131    /// This can be prohibitively expensive, depending on the
132    /// relocation model, and so on some targets it instead sniffs for
133    /// a particular instruction sequence.  This functions returns
134    /// that instruction sequence in inline assembly, which will be
135    /// empty if none is required.
136    virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
137      return "";
138    }
139
140    /// Return a constant used by UBSan as a signature to identify functions
141    /// possessing type information, or 0 if the platform is unsupported.
142    virtual llvm::Constant *getUBSanFunctionSignature(
143        CodeGen::CodeGenModule &CGM) const {
144      return 0;
145    }
146
147    /// Determine whether a call to an unprototyped functions under
148    /// the given calling convention should use the variadic
149    /// convention or the non-variadic convention.
150    ///
151    /// There's a good reason to make a platform's variadic calling
152    /// convention be different from its non-variadic calling
153    /// convention: the non-variadic arguments can be passed in
154    /// registers (better for performance), and the variadic arguments
155    /// can be passed on the stack (also better for performance).  If
156    /// this is done, however, unprototyped functions *must* use the
157    /// non-variadic convention, because C99 states that a call
158    /// through an unprototyped function type must succeed if the
159    /// function was defined with a non-variadic prototype with
160    /// compatible parameters.  Therefore, splitting the conventions
161    /// makes it impossible to call a variadic function through an
162    /// unprototyped type.  Since function prototypes came out in the
163    /// late 1970s, this is probably an acceptable trade-off.
164    /// Nonetheless, not all platforms are willing to make it, and in
165    /// particularly x86-64 bends over backwards to make the
166    /// conventions compatible.
167    ///
168    /// The default is false.  This is correct whenever:
169    ///   - the conventions are exactly the same, because it does not
170    ///     matter and the resulting IR will be somewhat prettier in
171    ///     certain cases; or
172    ///   - the conventions are substantively different in how they pass
173    ///     arguments, because in this case using the variadic convention
174    ///     will lead to C99 violations.
175    ///
176    /// However, some platforms make the conventions identical except
177    /// for passing additional out-of-band information to a variadic
178    /// function: for example, x86-64 passes the number of SSE
179    /// arguments in %al.  On these platforms, it is desireable to
180    /// call unprototyped functions using the variadic convention so
181    /// that unprototyped calls to varargs functions still succeed.
182    ///
183    /// Relatedly, platforms which pass the fixed arguments to this:
184    ///   A foo(B, C, D);
185    /// differently than they would pass them to this:
186    ///   A foo(B, C, D, ...);
187    /// may need to adjust the debugger-support code in Sema to do the
188    /// right thing when calling a function with no know signature.
189    virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
190                                       const FunctionNoProtoType *fnType) const;
191
192    /// Gets the linker options necessary to link a dependent library on this
193    /// platform.
194    virtual void getDependentLibraryOption(llvm::StringRef Lib,
195                                           llvm::SmallString<24> &Opt) const;
196
197    /// Gets the linker options necessary to detect object file mismatches on
198    /// this platform.
199    virtual void getDetectMismatchOption(llvm::StringRef Name,
200                                         llvm::StringRef Value,
201                                         llvm::SmallString<32> &Opt) const {}
202  };
203}
204
205#endif // CLANG_CODEGEN_TARGETINFO_H
206