xref: /freebsd/contrib/llvm-project/clang/lib/CodeGen/CGObjCRuntime.cpp (revision 6ba2210ee039f2f12878c217bcf058e9c8b26b29)
1 //==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
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 // This abstract class defines the interface for Objective-C runtime-specific
10 // code generation.  It provides some concrete helper methods for functionality
11 // shared between all (or most) of the Objective-C runtimes supported by clang.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "CGObjCRuntime.h"
16 #include "CGCXXABI.h"
17 #include "CGCleanup.h"
18 #include "CGRecordLayout.h"
19 #include "CodeGenFunction.h"
20 #include "CodeGenModule.h"
21 #include "clang/AST/RecordLayout.h"
22 #include "clang/AST/StmtObjC.h"
23 #include "clang/CodeGen/CGFunctionInfo.h"
24 #include "clang/CodeGen/CodeGenABITypes.h"
25 #include "llvm/Support/SaveAndRestore.h"
26 
27 using namespace clang;
28 using namespace CodeGen;
29 
30 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
31                                               const ObjCInterfaceDecl *OID,
32                                               const ObjCIvarDecl *Ivar) {
33   return CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar) /
34          CGM.getContext().getCharWidth();
35 }
36 
37 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
38                                               const ObjCImplementationDecl *OID,
39                                               const ObjCIvarDecl *Ivar) {
40   return CGM.getContext().lookupFieldBitOffset(OID->getClassInterface(), OID,
41                                                Ivar) /
42          CGM.getContext().getCharWidth();
43 }
44 
45 unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
46     CodeGen::CodeGenModule &CGM,
47     const ObjCInterfaceDecl *ID,
48     const ObjCIvarDecl *Ivar) {
49   return CGM.getContext().lookupFieldBitOffset(ID, ID->getImplementation(),
50                                                Ivar);
51 }
52 
53 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
54                                                const ObjCInterfaceDecl *OID,
55                                                llvm::Value *BaseValue,
56                                                const ObjCIvarDecl *Ivar,
57                                                unsigned CVRQualifiers,
58                                                llvm::Value *Offset) {
59   // Compute (type*) ( (char *) BaseValue + Offset)
60   QualType InterfaceTy{OID->getTypeForDecl(), 0};
61   QualType ObjectPtrTy =
62       CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);
63   QualType IvarTy =
64       Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);
65   llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
66   llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
67   V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr");
68 
69   if (!Ivar->isBitField()) {
70     V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
71     LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
72     return LV;
73   }
74 
75   // We need to compute an access strategy for this bit-field. We are given the
76   // offset to the first byte in the bit-field, the sub-byte offset is taken
77   // from the original layout. We reuse the normal bit-field access strategy by
78   // treating this as an access to a struct where the bit-field is in byte 0,
79   // and adjust the containing type size as appropriate.
80   //
81   // FIXME: Note that currently we make a very conservative estimate of the
82   // alignment of the bit-field, because (a) it is not clear what guarantees the
83   // runtime makes us, and (b) we don't have a way to specify that the struct is
84   // at an alignment plus offset.
85   //
86   // Note, there is a subtle invariant here: we can only call this routine on
87   // non-synthesized ivars but we may be called for synthesized ivars.  However,
88   // a synthesized ivar can never be a bit-field, so this is safe.
89   uint64_t FieldBitOffset =
90       CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);
91   uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
92   uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
93   uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
94   CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
95       llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));
96   CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
97 
98   // Allocate a new CGBitFieldInfo object to describe this access.
99   //
100   // FIXME: This is incredibly wasteful, these should be uniqued or part of some
101   // layout object. However, this is blocked on other cleanups to the
102   // Objective-C code, so for now we just live with allocating a bunch of these
103   // objects.
104   CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
105     CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
106                              CGF.CGM.getContext().toBits(StorageSize),
107                              CharUnits::fromQuantity(0)));
108 
109   Address Addr(V, Alignment);
110   Addr = CGF.Builder.CreateElementBitCast(Addr,
111                                    llvm::Type::getIntNTy(CGF.getLLVMContext(),
112                                                          Info->StorageSize));
113   return LValue::MakeBitfield(Addr, *Info, IvarTy,
114                               LValueBaseInfo(AlignmentSource::Decl),
115                               TBAAAccessInfo());
116 }
117 
118 namespace {
119   struct CatchHandler {
120     const VarDecl *Variable;
121     const Stmt *Body;
122     llvm::BasicBlock *Block;
123     llvm::Constant *TypeInfo;
124     /// Flags used to differentiate cleanups and catchalls in Windows SEH
125     unsigned Flags;
126   };
127 
128   struct CallObjCEndCatch final : EHScopeStack::Cleanup {
129     CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
130         : MightThrow(MightThrow), Fn(Fn) {}
131     bool MightThrow;
132     llvm::FunctionCallee Fn;
133 
134     void Emit(CodeGenFunction &CGF, Flags flags) override {
135       if (MightThrow)
136         CGF.EmitRuntimeCallOrInvoke(Fn);
137       else
138         CGF.EmitNounwindRuntimeCall(Fn);
139     }
140   };
141 }
142 
143 void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
144                                      const ObjCAtTryStmt &S,
145                                      llvm::FunctionCallee beginCatchFn,
146                                      llvm::FunctionCallee endCatchFn,
147                                      llvm::FunctionCallee exceptionRethrowFn) {
148   // Jump destination for falling out of catch bodies.
149   CodeGenFunction::JumpDest Cont;
150   if (S.getNumCatchStmts())
151     Cont = CGF.getJumpDestInCurrentScope("eh.cont");
152 
153   bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
154 
155   CodeGenFunction::FinallyInfo FinallyInfo;
156   if (!useFunclets)
157     if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
158       FinallyInfo.enter(CGF, Finally->getFinallyBody(),
159                         beginCatchFn, endCatchFn, exceptionRethrowFn);
160 
161   SmallVector<CatchHandler, 8> Handlers;
162 
163 
164   // Enter the catch, if there is one.
165   if (S.getNumCatchStmts()) {
166     for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) {
167       const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I);
168       const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
169 
170       Handlers.push_back(CatchHandler());
171       CatchHandler &Handler = Handlers.back();
172       Handler.Variable = CatchDecl;
173       Handler.Body = CatchStmt->getCatchBody();
174       Handler.Block = CGF.createBasicBlock("catch");
175       Handler.Flags = 0;
176 
177       // @catch(...) always matches.
178       if (!CatchDecl) {
179         auto catchAll = getCatchAllTypeInfo();
180         Handler.TypeInfo = catchAll.RTTI;
181         Handler.Flags = catchAll.Flags;
182         // Don't consider any other catches.
183         break;
184       }
185 
186       Handler.TypeInfo = GetEHType(CatchDecl->getType());
187     }
188 
189     EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
190     for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
191       Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);
192   }
193 
194   if (useFunclets)
195     if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
196         CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
197         if (!CGF.CurSEHParent)
198             CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);
199         // Outline the finally block.
200         const Stmt *FinallyBlock = Finally->getFinallyBody();
201         HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);
202 
203         // Emit the original filter expression, convert to i32, and return.
204         HelperCGF.EmitStmt(FinallyBlock);
205 
206         HelperCGF.FinishFunction(FinallyBlock->getEndLoc());
207 
208         llvm::Function *FinallyFunc = HelperCGF.CurFn;
209 
210 
211         // Push a cleanup for __finally blocks.
212         CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);
213     }
214 
215 
216   // Emit the try body.
217   CGF.EmitStmt(S.getTryBody());
218 
219   // Leave the try.
220   if (S.getNumCatchStmts())
221     CGF.popCatchScope();
222 
223   // Remember where we were.
224   CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
225 
226   // Emit the handlers.
227   for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
228     CatchHandler &Handler = Handlers[I];
229 
230     CGF.EmitBlock(Handler.Block);
231     llvm::CatchPadInst *CPI = nullptr;
232     SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(CGF.CurrentFuncletPad);
233     if (useFunclets)
234       if ((CPI = dyn_cast_or_null<llvm::CatchPadInst>(Handler.Block->getFirstNonPHI()))) {
235         CGF.CurrentFuncletPad = CPI;
236         CPI->setOperand(2, CGF.getExceptionSlot().getPointer());
237       }
238     llvm::Value *RawExn = CGF.getExceptionFromSlot();
239 
240     // Enter the catch.
241     llvm::Value *Exn = RawExn;
242     if (beginCatchFn)
243       Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");
244 
245     CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange());
246 
247     if (endCatchFn) {
248       // Add a cleanup to leave the catch.
249       bool EndCatchMightThrow = (Handler.Variable == nullptr);
250 
251       CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
252                                                 EndCatchMightThrow,
253                                                 endCatchFn);
254     }
255 
256     // Bind the catch parameter if it exists.
257     if (const VarDecl *CatchParam = Handler.Variable) {
258       llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
259       llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
260 
261       CGF.EmitAutoVarDecl(*CatchParam);
262       EmitInitOfCatchParam(CGF, CastExn, CatchParam);
263     }
264     if (CPI)
265         CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
266 
267     CGF.ObjCEHValueStack.push_back(Exn);
268     CGF.EmitStmt(Handler.Body);
269     CGF.ObjCEHValueStack.pop_back();
270 
271     // Leave any cleanups associated with the catch.
272     cleanups.ForceCleanup();
273 
274     CGF.EmitBranchThroughCleanup(Cont);
275   }
276 
277   // Go back to the try-statement fallthrough.
278   CGF.Builder.restoreIP(SavedIP);
279 
280   // Pop out of the finally.
281   if (!useFunclets && S.getFinallyStmt())
282     FinallyInfo.exit(CGF);
283 
284   if (Cont.isValid())
285     CGF.EmitBlock(Cont.getBlock());
286 }
287 
288 void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
289                                          llvm::Value *exn,
290                                          const VarDecl *paramDecl) {
291 
292   Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
293 
294   switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
295   case Qualifiers::OCL_Strong:
296     exn = CGF.EmitARCRetainNonBlock(exn);
297     LLVM_FALLTHROUGH;
298 
299   case Qualifiers::OCL_None:
300   case Qualifiers::OCL_ExplicitNone:
301   case Qualifiers::OCL_Autoreleasing:
302     CGF.Builder.CreateStore(exn, paramAddr);
303     return;
304 
305   case Qualifiers::OCL_Weak:
306     CGF.EmitARCInitWeak(paramAddr, exn);
307     return;
308   }
309   llvm_unreachable("invalid ownership qualifier");
310 }
311 
312 namespace {
313   struct CallSyncExit final : EHScopeStack::Cleanup {
314     llvm::FunctionCallee SyncExitFn;
315     llvm::Value *SyncArg;
316     CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
317         : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
318 
319     void Emit(CodeGenFunction &CGF, Flags flags) override {
320       CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);
321     }
322   };
323 }
324 
325 void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
326                                            const ObjCAtSynchronizedStmt &S,
327                                            llvm::FunctionCallee syncEnterFn,
328                                            llvm::FunctionCallee syncExitFn) {
329   CodeGenFunction::RunCleanupsScope cleanups(CGF);
330 
331   // Evaluate the lock operand.  This is guaranteed to dominate the
332   // ARC release and lock-release cleanups.
333   const Expr *lockExpr = S.getSynchExpr();
334   llvm::Value *lock;
335   if (CGF.getLangOpts().ObjCAutoRefCount) {
336     lock = CGF.EmitARCRetainScalarExpr(lockExpr);
337     lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
338   } else {
339     lock = CGF.EmitScalarExpr(lockExpr);
340   }
341   lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
342 
343   // Acquire the lock.
344   CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
345 
346   // Register an all-paths cleanup to release the lock.
347   CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
348 
349   // Emit the body of the statement.
350   CGF.EmitStmt(S.getSynchBody());
351 }
352 
353 /// Compute the pointer-to-function type to which a message send
354 /// should be casted in order to correctly call the given method
355 /// with the given arguments.
356 ///
357 /// \param method - may be null
358 /// \param resultType - the result type to use if there's no method
359 /// \param callArgs - the actual arguments, including implicit ones
360 CGObjCRuntime::MessageSendInfo
361 CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
362                                   QualType resultType,
363                                   CallArgList &callArgs) {
364   // If there's a method, use information from that.
365   if (method) {
366     const CGFunctionInfo &signature =
367       CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
368 
369     llvm::PointerType *signatureType =
370       CGM.getTypes().GetFunctionType(signature)->getPointerTo();
371 
372     const CGFunctionInfo &signatureForCall =
373       CGM.getTypes().arrangeCall(signature, callArgs);
374 
375     return MessageSendInfo(signatureForCall, signatureType);
376   }
377 
378   // There's no method;  just use a default CC.
379   const CGFunctionInfo &argsInfo =
380     CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);
381 
382   // Derive the signature to call from that.
383   llvm::PointerType *signatureType =
384     CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
385   return MessageSendInfo(argsInfo, signatureType);
386 }
387 
388 llvm::Constant *
389 clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
390                                        const ObjCProtocolDecl *protocol) {
391   return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);
392 }
393 
394 std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
395                                                   bool includeCategoryName) {
396   std::string buffer;
397   llvm::raw_string_ostream out(buffer);
398   CGM.getCXXABI().getMangleContext().mangleObjCMethodName(OMD, out,
399                                        /*includePrefixByte=*/true,
400                                        includeCategoryName);
401   return buffer;
402 }
403