1 //===---- TargetInfo.h - Encapsulate target details -------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // These classes wrap the information about a call or function
11 // definition used to handle ABI compliancy.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
16 #define LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
19 #include "clang/AST/Type.h"
20 #include "clang/Basic/LLVM.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/ADT/StringRef.h"
38 class CodeGenFunction;
42 /// TargetCodeGenInfo - This class organizes various target-specific
43 /// codegeneration issues, like target-specific attributes, builtins and so
45 class TargetCodeGenInfo {
49 // WARNING: Acquires the ownership of ABIInfo.
50 TargetCodeGenInfo(ABIInfo *info = nullptr) : Info(info) {}
51 virtual ~TargetCodeGenInfo();
53 /// getABIInfo() - Returns ABI info helper for the target.
54 const ABIInfo &getABIInfo() const { return *Info; }
56 /// setTargetAttributes - Provides a convenient hook to handle extra
57 /// target-specific attributes for the given global.
58 virtual void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
59 CodeGen::CodeGenModule &M) const {}
61 /// emitTargetMD - Provides a convenient hook to handle extra
62 /// target-specific metadata for the given global.
63 virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
64 CodeGen::CodeGenModule &M) const {}
66 /// Determines the size of struct _Unwind_Exception on this platform,
67 /// in 8-bit units. The Itanium ABI defines this as:
68 /// struct _Unwind_Exception {
69 /// uint64 exception_class;
70 /// _Unwind_Exception_Cleanup_Fn exception_cleanup;
74 virtual unsigned getSizeOfUnwindException() const;
76 /// Controls whether __builtin_extend_pointer should sign-extend
77 /// pointers to uint64_t or zero-extend them (the default). Has
78 /// no effect for targets:
79 /// - that have 64-bit pointers, or
80 /// - that cannot address through registers larger than pointers, or
81 /// - that implicitly ignore/truncate the top bits when addressing
82 /// through such registers.
83 virtual bool extendPointerWithSExt() const { return false; }
85 /// Determines the DWARF register number for the stack pointer, for
86 /// exception-handling purposes. Implements __builtin_dwarf_sp_column.
88 /// Returns -1 if the operation is unsupported by this target.
89 virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
93 /// Initializes the given DWARF EH register-size table, a char*.
94 /// Implements __builtin_init_dwarf_reg_size_table.
96 /// Returns true if the operation is unsupported by this target.
97 virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
98 llvm::Value *Address) const {
102 /// Performs the code-generation required to convert a return
103 /// address as stored by the system into the actual address of the
104 /// next instruction that will be executed.
106 /// Used by __builtin_extract_return_addr().
107 virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
108 llvm::Value *Address) const {
112 /// Performs the code-generation required to convert the address
113 /// of an instruction into a return address suitable for storage
114 /// by the system in a return slot.
116 /// Used by __builtin_frob_return_addr().
117 virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
118 llvm::Value *Address) const {
122 /// Corrects the low-level LLVM type for a given constraint and "usual"
125 /// \returns A pointer to a new LLVM type, possibly the same as the original
126 /// on success; 0 on failure.
127 virtual llvm::Type *adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
128 StringRef Constraint,
129 llvm::Type *Ty) const {
133 /// Adds constraints and types for result registers.
134 virtual void addReturnRegisterOutputs(
135 CodeGen::CodeGenFunction &CGF, CodeGen::LValue ReturnValue,
136 std::string &Constraints, std::vector<llvm::Type *> &ResultRegTypes,
137 std::vector<llvm::Type *> &ResultTruncRegTypes,
138 std::vector<CodeGen::LValue> &ResultRegDests, std::string &AsmString,
139 unsigned NumOutputs) const {}
141 /// doesReturnSlotInterfereWithArgs - Return true if the target uses an
142 /// argument slot for an 'sret' type.
143 virtual bool doesReturnSlotInterfereWithArgs() const { return true; }
145 /// Retrieve the address of a function to call immediately before
146 /// calling objc_retainAutoreleasedReturnValue. The
147 /// implementation of objc_autoreleaseReturnValue sniffs the
148 /// instruction stream following its return address to decide
149 /// whether it's a call to objc_retainAutoreleasedReturnValue.
150 /// This can be prohibitively expensive, depending on the
151 /// relocation model, and so on some targets it instead sniffs for
152 /// a particular instruction sequence. This functions returns
153 /// that instruction sequence in inline assembly, which will be
154 /// empty if none is required.
155 virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
159 /// Return a constant used by UBSan as a signature to identify functions
160 /// possessing type information, or 0 if the platform is unsupported.
161 virtual llvm::Constant *
162 getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const {
166 /// Determine whether a call to an unprototyped functions under
167 /// the given calling convention should use the variadic
168 /// convention or the non-variadic convention.
170 /// There's a good reason to make a platform's variadic calling
171 /// convention be different from its non-variadic calling
172 /// convention: the non-variadic arguments can be passed in
173 /// registers (better for performance), and the variadic arguments
174 /// can be passed on the stack (also better for performance). If
175 /// this is done, however, unprototyped functions *must* use the
176 /// non-variadic convention, because C99 states that a call
177 /// through an unprototyped function type must succeed if the
178 /// function was defined with a non-variadic prototype with
179 /// compatible parameters. Therefore, splitting the conventions
180 /// makes it impossible to call a variadic function through an
181 /// unprototyped type. Since function prototypes came out in the
182 /// late 1970s, this is probably an acceptable trade-off.
183 /// Nonetheless, not all platforms are willing to make it, and in
184 /// particularly x86-64 bends over backwards to make the
185 /// conventions compatible.
187 /// The default is false. This is correct whenever:
188 /// - the conventions are exactly the same, because it does not
189 /// matter and the resulting IR will be somewhat prettier in
190 /// certain cases; or
191 /// - the conventions are substantively different in how they pass
192 /// arguments, because in this case using the variadic convention
193 /// will lead to C99 violations.
195 /// However, some platforms make the conventions identical except
196 /// for passing additional out-of-band information to a variadic
197 /// function: for example, x86-64 passes the number of SSE
198 /// arguments in %al. On these platforms, it is desirable to
199 /// call unprototyped functions using the variadic convention so
200 /// that unprototyped calls to varargs functions still succeed.
202 /// Relatedly, platforms which pass the fixed arguments to this:
204 /// differently than they would pass them to this:
205 /// A foo(B, C, D, ...);
206 /// may need to adjust the debugger-support code in Sema to do the
207 /// right thing when calling a function with no know signature.
208 virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
209 const FunctionNoProtoType *fnType) const;
211 /// Gets the linker options necessary to link a dependent library on this
213 virtual void getDependentLibraryOption(llvm::StringRef Lib,
214 llvm::SmallString<24> &Opt) const;
216 /// Gets the linker options necessary to detect object file mismatches on
218 virtual void getDetectMismatchOption(llvm::StringRef Name,
219 llvm::StringRef Value,
220 llvm::SmallString<32> &Opt) const {}
224 #endif // LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H