1 //===---- TargetInfo.h - Encapsulate target details -------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // These classes wrap the information about a call or function
10 // definition used to handle ABI compliancy.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
15 #define LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
16 
17 #include "CodeGenModule.h"
18 #include "CGValue.h"
19 #include "clang/AST/Type.h"
20 #include "clang/Basic/LLVM.h"
21 #include "clang/Basic/SyncScope.h"
22 #include "llvm/ADT/SmallString.h"
23 #include "llvm/ADT/StringRef.h"
24 
25 namespace llvm {
26 class Constant;
27 class GlobalValue;
28 class Type;
29 class Value;
30 }
31 
32 namespace clang {
33 class Decl;
34 
35 namespace CodeGen {
36 class ABIInfo;
37 class CallArgList;
38 class CodeGenFunction;
39 class CGBlockInfo;
40 class CGFunctionInfo;
41 
42 /// TargetCodeGenInfo - This class organizes various target-specific
43 /// codegeneration issues, like target-specific attributes, builtins and so
44 /// on.
45 class TargetCodeGenInfo {
46   ABIInfo *Info;
47 
48 public:
49   // WARNING: Acquires the ownership of ABIInfo.
50   TargetCodeGenInfo(ABIInfo *info = nullptr) : Info(info) {}
51   virtual ~TargetCodeGenInfo();
52 
53   /// getABIInfo() - Returns ABI info helper for the target.
54   const ABIInfo &getABIInfo() const { return *Info; }
55 
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 {}
60 
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 {}
65 
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;
71   ///     uint64 private_1;
72   ///     uint64 private_2;
73   ///   };
74   virtual unsigned getSizeOfUnwindException() const;
75 
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; }
84 
85   /// Determines the DWARF register number for the stack pointer, for
86   /// exception-handling purposes.  Implements __builtin_dwarf_sp_column.
87   ///
88   /// Returns -1 if the operation is unsupported by this target.
89   virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
90     return -1;
91   }
92 
93   /// Initializes the given DWARF EH register-size table, a char*.
94   /// Implements __builtin_init_dwarf_reg_size_table.
95   ///
96   /// Returns true if the operation is unsupported by this target.
97   virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
98                                        llvm::Value *Address) const {
99     return true;
100   }
101 
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.
105   ///
106   /// Used by __builtin_extract_return_addr().
107   virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
108                                            llvm::Value *Address) const {
109     return Address;
110   }
111 
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.
115   ///
116   /// Used by __builtin_frob_return_addr().
117   virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
118                                            llvm::Value *Address) const {
119     return Address;
120   }
121 
122   /// Corrects the low-level LLVM type for a given constraint and "usual"
123   /// type.
124   ///
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 {
130     return Ty;
131   }
132 
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 {}
140 
141   /// doesReturnSlotInterfereWithArgs - Return true if the target uses an
142   /// argument slot for an 'sret' type.
143   virtual bool doesReturnSlotInterfereWithArgs() const { return true; }
144 
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 {
156     return "";
157   }
158 
159   /// Determine whether a call to objc_retainAutoreleasedReturnValue should be
160   /// marked as 'notail'.
161   virtual bool shouldSuppressTailCallsOfRetainAutoreleasedReturnValue() const {
162     return false;
163   }
164 
165   /// Return a constant used by UBSan as a signature to identify functions
166   /// possessing type information, or 0 if the platform is unsupported.
167   virtual llvm::Constant *
168   getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const {
169     return nullptr;
170   }
171 
172   /// Determine whether a call to an unprototyped functions under
173   /// the given calling convention should use the variadic
174   /// convention or the non-variadic convention.
175   ///
176   /// There's a good reason to make a platform's variadic calling
177   /// convention be different from its non-variadic calling
178   /// convention: the non-variadic arguments can be passed in
179   /// registers (better for performance), and the variadic arguments
180   /// can be passed on the stack (also better for performance).  If
181   /// this is done, however, unprototyped functions *must* use the
182   /// non-variadic convention, because C99 states that a call
183   /// through an unprototyped function type must succeed if the
184   /// function was defined with a non-variadic prototype with
185   /// compatible parameters.  Therefore, splitting the conventions
186   /// makes it impossible to call a variadic function through an
187   /// unprototyped type.  Since function prototypes came out in the
188   /// late 1970s, this is probably an acceptable trade-off.
189   /// Nonetheless, not all platforms are willing to make it, and in
190   /// particularly x86-64 bends over backwards to make the
191   /// conventions compatible.
192   ///
193   /// The default is false.  This is correct whenever:
194   ///   - the conventions are exactly the same, because it does not
195   ///     matter and the resulting IR will be somewhat prettier in
196   ///     certain cases; or
197   ///   - the conventions are substantively different in how they pass
198   ///     arguments, because in this case using the variadic convention
199   ///     will lead to C99 violations.
200   ///
201   /// However, some platforms make the conventions identical except
202   /// for passing additional out-of-band information to a variadic
203   /// function: for example, x86-64 passes the number of SSE
204   /// arguments in %al.  On these platforms, it is desirable to
205   /// call unprototyped functions using the variadic convention so
206   /// that unprototyped calls to varargs functions still succeed.
207   ///
208   /// Relatedly, platforms which pass the fixed arguments to this:
209   ///   A foo(B, C, D);
210   /// differently than they would pass them to this:
211   ///   A foo(B, C, D, ...);
212   /// may need to adjust the debugger-support code in Sema to do the
213   /// right thing when calling a function with no know signature.
214   virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
215                                      const FunctionNoProtoType *fnType) const;
216 
217   /// Gets the linker options necessary to link a dependent library on this
218   /// platform.
219   virtual void getDependentLibraryOption(llvm::StringRef Lib,
220                                          llvm::SmallString<24> &Opt) const;
221 
222   /// Gets the linker options necessary to detect object file mismatches on
223   /// this platform.
224   virtual void getDetectMismatchOption(llvm::StringRef Name,
225                                        llvm::StringRef Value,
226                                        llvm::SmallString<32> &Opt) const {}
227 
228   /// Get LLVM calling convention for OpenCL kernel.
229   virtual unsigned getOpenCLKernelCallingConv() const;
230 
231   /// Get target specific null pointer.
232   /// \param T is the LLVM type of the null pointer.
233   /// \param QT is the clang QualType of the null pointer.
234   /// \return ConstantPointerNull with the given type \p T.
235   /// Each target can override it to return its own desired constant value.
236   virtual llvm::Constant *getNullPointer(const CodeGen::CodeGenModule &CGM,
237       llvm::PointerType *T, QualType QT) const;
238 
239   /// Get target favored AST address space of a global variable for languages
240   /// other than OpenCL and CUDA.
241   /// If \p D is nullptr, returns the default target favored address space
242   /// for global variable.
243   virtual LangAS getGlobalVarAddressSpace(CodeGenModule &CGM,
244                                           const VarDecl *D) const;
245 
246   /// Get the AST address space for alloca.
247   virtual LangAS getASTAllocaAddressSpace() const { return LangAS::Default; }
248 
249   /// Perform address space cast of an expression of pointer type.
250   /// \param V is the LLVM value to be casted to another address space.
251   /// \param SrcAddr is the language address space of \p V.
252   /// \param DestAddr is the targeted language address space.
253   /// \param DestTy is the destination LLVM pointer type.
254   /// \param IsNonNull is the flag indicating \p V is known to be non null.
255   virtual llvm::Value *performAddrSpaceCast(CodeGen::CodeGenFunction &CGF,
256                                             llvm::Value *V, LangAS SrcAddr,
257                                             LangAS DestAddr, llvm::Type *DestTy,
258                                             bool IsNonNull = false) const;
259 
260   /// Perform address space cast of a constant expression of pointer type.
261   /// \param V is the LLVM constant to be casted to another address space.
262   /// \param SrcAddr is the language address space of \p V.
263   /// \param DestAddr is the targeted language address space.
264   /// \param DestTy is the destination LLVM pointer type.
265   virtual llvm::Constant *performAddrSpaceCast(CodeGenModule &CGM,
266                                                llvm::Constant *V,
267                                                LangAS SrcAddr, LangAS DestAddr,
268                                                llvm::Type *DestTy) const;
269 
270   /// Get address space of pointer parameter for __cxa_atexit.
271   virtual LangAS getAddrSpaceOfCxaAtexitPtrParam() const {
272     return LangAS::Default;
273   }
274 
275   /// Get the syncscope used in LLVM IR.
276   virtual llvm::SyncScope::ID getLLVMSyncScopeID(const LangOptions &LangOpts,
277                                                  SyncScope Scope,
278                                                  llvm::AtomicOrdering Ordering,
279                                                  llvm::LLVMContext &Ctx) const;
280 
281   /// Interface class for filling custom fields of a block literal for OpenCL.
282   class TargetOpenCLBlockHelper {
283   public:
284     typedef std::pair<llvm::Value *, StringRef> ValueTy;
285     TargetOpenCLBlockHelper() {}
286     virtual ~TargetOpenCLBlockHelper() {}
287     /// Get the custom field types for OpenCL blocks.
288     virtual llvm::SmallVector<llvm::Type *, 1> getCustomFieldTypes() = 0;
289     /// Get the custom field values for OpenCL blocks.
290     virtual llvm::SmallVector<ValueTy, 1>
291     getCustomFieldValues(CodeGenFunction &CGF, const CGBlockInfo &Info) = 0;
292     virtual bool areAllCustomFieldValuesConstant(const CGBlockInfo &Info) = 0;
293     /// Get the custom field values for OpenCL blocks if all values are LLVM
294     /// constants.
295     virtual llvm::SmallVector<llvm::Constant *, 1>
296     getCustomFieldValues(CodeGenModule &CGM, const CGBlockInfo &Info) = 0;
297   };
298   virtual TargetOpenCLBlockHelper *getTargetOpenCLBlockHelper() const {
299     return nullptr;
300   }
301 
302   /// Create an OpenCL kernel for an enqueued block. The kernel function is
303   /// a wrapper for the block invoke function with target-specific calling
304   /// convention and ABI as an OpenCL kernel. The wrapper function accepts
305   /// block context and block arguments in target-specific way and calls
306   /// the original block invoke function.
307   virtual llvm::Function *
308   createEnqueuedBlockKernel(CodeGenFunction &CGF,
309                             llvm::Function *BlockInvokeFunc,
310                             llvm::Value *BlockLiteral) const;
311 
312   /// \return true if the target supports alias from the unmangled name to the
313   /// mangled name of functions declared within an extern "C" region and marked
314   /// as 'used', and having internal linkage.
315   virtual bool shouldEmitStaticExternCAliases() const { return true; }
316 
317   virtual void setCUDAKernelCallingConvention(const FunctionType *&FT) const {}
318 };
319 
320 } // namespace CodeGen
321 } // namespace clang
322 
323 #endif // LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
324