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