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;
41 /// TargetCodeGenInfo - This class organizes various target-specific
42 /// codegeneration issues, like target-specific attributes, builtins and so
44 class TargetCodeGenInfo {
48 // WARNING: Acquires the ownership of ABIInfo.
49 TargetCodeGenInfo(ABIInfo *info = nullptr) : Info(info) {}
50 virtual ~TargetCodeGenInfo();
52 /// getABIInfo() - Returns ABI info helper for the target.
53 const ABIInfo &getABIInfo() const { return *Info; }
55 /// setTargetAttributes - Provides a convenient hook to handle extra
56 /// target-specific attributes for the given global.
57 virtual void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
58 CodeGen::CodeGenModule &M) const {}
60 /// emitTargetMD - Provides a convenient hook to handle extra
61 /// target-specific metadata for the given global.
62 virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
63 CodeGen::CodeGenModule &M) const {}
65 /// Determines the size of struct _Unwind_Exception on this platform,
66 /// in 8-bit units. The Itanium ABI defines this as:
67 /// struct _Unwind_Exception {
68 /// uint64 exception_class;
69 /// _Unwind_Exception_Cleanup_Fn exception_cleanup;
73 virtual unsigned getSizeOfUnwindException() const;
75 /// Controls whether __builtin_extend_pointer should sign-extend
76 /// pointers to uint64_t or zero-extend them (the default). Has
77 /// no effect for targets:
78 /// - that have 64-bit pointers, or
79 /// - that cannot address through registers larger than pointers, or
80 /// - that implicitly ignore/truncate the top bits when addressing
81 /// through such registers.
82 virtual bool extendPointerWithSExt() const { return false; }
84 /// Determines the DWARF register number for the stack pointer, for
85 /// exception-handling purposes. Implements __builtin_dwarf_sp_column.
87 /// Returns -1 if the operation is unsupported by this target.
88 virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
92 /// Initializes the given DWARF EH register-size table, a char*.
93 /// Implements __builtin_init_dwarf_reg_size_table.
95 /// Returns true if the operation is unsupported by this target.
96 virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
97 llvm::Value *Address) const {
101 /// Performs the code-generation required to convert a return
102 /// address as stored by the system into the actual address of the
103 /// next instruction that will be executed.
105 /// Used by __builtin_extract_return_addr().
106 virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
107 llvm::Value *Address) const {
111 /// Performs the code-generation required to convert the address
112 /// of an instruction into a return address suitable for storage
113 /// by the system in a return slot.
115 /// Used by __builtin_frob_return_addr().
116 virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
117 llvm::Value *Address) const {
121 /// Corrects the low-level LLVM type for a given constraint and "usual"
124 /// \returns A pointer to a new LLVM type, possibly the same as the original
125 /// on success; 0 on failure.
126 virtual llvm::Type *adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
127 StringRef Constraint,
128 llvm::Type *Ty) const {
132 /// Adds constraints and types for result registers.
133 virtual void addReturnRegisterOutputs(
134 CodeGen::CodeGenFunction &CGF, CodeGen::LValue ReturnValue,
135 std::string &Constraints, std::vector<llvm::Type *> &ResultRegTypes,
136 std::vector<llvm::Type *> &ResultTruncRegTypes,
137 std::vector<CodeGen::LValue> &ResultRegDests, std::string &AsmString,
138 unsigned NumOutputs) const {}
140 /// doesReturnSlotInterfereWithArgs - Return true if the target uses an
141 /// argument slot for an 'sret' type.
142 virtual bool doesReturnSlotInterfereWithArgs() const { return true; }
144 /// Retrieve the address of a function to call immediately before
145 /// calling objc_retainAutoreleasedReturnValue. The
146 /// implementation of objc_autoreleaseReturnValue sniffs the
147 /// instruction stream following its return address to decide
148 /// whether it's a call to objc_retainAutoreleasedReturnValue.
149 /// This can be prohibitively expensive, depending on the
150 /// relocation model, and so on some targets it instead sniffs for
151 /// a particular instruction sequence. This functions returns
152 /// that instruction sequence in inline assembly, which will be
153 /// empty if none is required.
154 virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
158 /// Return a constant used by UBSan as a signature to identify functions
159 /// possessing type information, or 0 if the platform is unsupported.
160 virtual llvm::Constant *
161 getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const {
165 /// Determine whether a call to an unprototyped functions under
166 /// the given calling convention should use the variadic
167 /// convention or the non-variadic convention.
169 /// There's a good reason to make a platform's variadic calling
170 /// convention be different from its non-variadic calling
171 /// convention: the non-variadic arguments can be passed in
172 /// registers (better for performance), and the variadic arguments
173 /// can be passed on the stack (also better for performance). If
174 /// this is done, however, unprototyped functions *must* use the
175 /// non-variadic convention, because C99 states that a call
176 /// through an unprototyped function type must succeed if the
177 /// function was defined with a non-variadic prototype with
178 /// compatible parameters. Therefore, splitting the conventions
179 /// makes it impossible to call a variadic function through an
180 /// unprototyped type. Since function prototypes came out in the
181 /// late 1970s, this is probably an acceptable trade-off.
182 /// Nonetheless, not all platforms are willing to make it, and in
183 /// particularly x86-64 bends over backwards to make the
184 /// conventions compatible.
186 /// The default is false. This is correct whenever:
187 /// - the conventions are exactly the same, because it does not
188 /// matter and the resulting IR will be somewhat prettier in
189 /// certain cases; or
190 /// - the conventions are substantively different in how they pass
191 /// arguments, because in this case using the variadic convention
192 /// will lead to C99 violations.
194 /// However, some platforms make the conventions identical except
195 /// for passing additional out-of-band information to a variadic
196 /// function: for example, x86-64 passes the number of SSE
197 /// arguments in %al. On these platforms, it is desirable to
198 /// call unprototyped functions using the variadic convention so
199 /// that unprototyped calls to varargs functions still succeed.
201 /// Relatedly, platforms which pass the fixed arguments to this:
203 /// differently than they would pass them to this:
204 /// A foo(B, C, D, ...);
205 /// may need to adjust the debugger-support code in Sema to do the
206 /// right thing when calling a function with no know signature.
207 virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
208 const FunctionNoProtoType *fnType) const;
210 /// Gets the linker options necessary to link a dependent library on this
212 virtual void getDependentLibraryOption(llvm::StringRef Lib,
213 llvm::SmallString<24> &Opt) const;
215 /// Gets the linker options necessary to detect object file mismatches on
217 virtual void getDetectMismatchOption(llvm::StringRef Name,
218 llvm::StringRef Value,
219 llvm::SmallString<32> &Opt) const {}
221 /// Get LLVM calling convention for OpenCL kernel.
222 virtual unsigned getOpenCLKernelCallingConv() const;
224 /// Get target specific null pointer.
225 /// \param T is the LLVM type of the null pointer.
226 /// \param QT is the clang QualType of the null pointer.
227 /// \return ConstantPointerNull with the given type \p T.
228 /// Each target can override it to return its own desired constant value.
229 virtual llvm::Constant *getNullPointer(const CodeGen::CodeGenModule &CGM,
230 llvm::PointerType *T, QualType QT) const;
232 /// Perform address space cast of an expression of pointer type.
233 /// \param V is the LLVM value to be casted to another address space.
234 /// \param SrcTy is the QualType of \p V.
235 /// \param DestTy is the destination QualType.
236 virtual llvm::Value *performAddrSpaceCast(CodeGen::CodeGenFunction &CGF,
237 llvm::Value *V, QualType SrcTy, QualType DestTy) const;
241 } // namespace CodeGen
244 #endif // LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H