1 //===- PreISelIntrinsicLowering.cpp - Pre-ISel intrinsic lowering pass ----===//
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 pass implements IR lowering for the llvm.load.relative and llvm.objc.*
10 // intrinsics.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/CodeGen/PreISelIntrinsicLowering.h"
15 #include "llvm/Analysis/ObjCARCInstKind.h"
16 #include "llvm/CodeGen/Passes.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/IRBuilder.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/Intrinsics.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/IR/Type.h"
23 #include "llvm/IR/User.h"
24 #include "llvm/InitializePasses.h"
25 #include "llvm/Pass.h"
26 #include "llvm/Support/Casting.h"
27 
28 using namespace llvm;
29 
30 static bool lowerLoadRelative(Function &F) {
31   if (F.use_empty())
32     return false;
33 
34   bool Changed = false;
35   Type *Int32Ty = Type::getInt32Ty(F.getContext());
36   Type *Int32PtrTy = Int32Ty->getPointerTo();
37   Type *Int8Ty = Type::getInt8Ty(F.getContext());
38 
39   for (auto I = F.use_begin(), E = F.use_end(); I != E;) {
40     auto CI = dyn_cast<CallInst>(I->getUser());
41     ++I;
42     if (!CI || CI->getCalledValue() != &F)
43       continue;
44 
45     IRBuilder<> B(CI);
46     Value *OffsetPtr =
47         B.CreateGEP(Int8Ty, CI->getArgOperand(0), CI->getArgOperand(1));
48     Value *OffsetPtrI32 = B.CreateBitCast(OffsetPtr, Int32PtrTy);
49     Value *OffsetI32 = B.CreateAlignedLoad(Int32Ty, OffsetPtrI32, 4);
50 
51     Value *ResultPtr = B.CreateGEP(Int8Ty, CI->getArgOperand(0), OffsetI32);
52 
53     CI->replaceAllUsesWith(ResultPtr);
54     CI->eraseFromParent();
55     Changed = true;
56   }
57 
58   return Changed;
59 }
60 
61 // ObjCARC has knowledge about whether an obj-c runtime function needs to be
62 // always tail-called or never tail-called.
63 static CallInst::TailCallKind getOverridingTailCallKind(const Function &F) {
64   objcarc::ARCInstKind Kind = objcarc::GetFunctionClass(&F);
65   if (objcarc::IsAlwaysTail(Kind))
66     return CallInst::TCK_Tail;
67   else if (objcarc::IsNeverTail(Kind))
68     return CallInst::TCK_NoTail;
69   return CallInst::TCK_None;
70 }
71 
72 static bool lowerObjCCall(Function &F, const char *NewFn,
73                           bool setNonLazyBind = false) {
74   if (F.use_empty())
75     return false;
76 
77   // If we haven't already looked up this function, check to see if the
78   // program already contains a function with this name.
79   Module *M = F.getParent();
80   FunctionCallee FCache = M->getOrInsertFunction(NewFn, F.getFunctionType());
81 
82   if (Function *Fn = dyn_cast<Function>(FCache.getCallee())) {
83     Fn->setLinkage(F.getLinkage());
84     if (setNonLazyBind && !Fn->isWeakForLinker()) {
85       // If we have Native ARC, set nonlazybind attribute for these APIs for
86       // performance.
87       Fn->addFnAttr(Attribute::NonLazyBind);
88     }
89   }
90 
91   CallInst::TailCallKind OverridingTCK = getOverridingTailCallKind(F);
92 
93   for (auto I = F.use_begin(), E = F.use_end(); I != E;) {
94     auto *CI = cast<CallInst>(I->getUser());
95     assert(CI->getCalledFunction() && "Cannot lower an indirect call!");
96     ++I;
97 
98     IRBuilder<> Builder(CI->getParent(), CI->getIterator());
99     SmallVector<Value *, 8> Args(CI->arg_begin(), CI->arg_end());
100     CallInst *NewCI = Builder.CreateCall(FCache, Args);
101     NewCI->setName(CI->getName());
102 
103     // Try to set the most appropriate TailCallKind based on both the current
104     // attributes and the ones that we could get from ObjCARC's special
105     // knowledge of the runtime functions.
106     //
107     // std::max respects both requirements of notail and tail here:
108     // * notail on either the call or from ObjCARC becomes notail
109     // * tail on either side is stronger than none, but not notail
110     CallInst::TailCallKind TCK = CI->getTailCallKind();
111     NewCI->setTailCallKind(std::max(TCK, OverridingTCK));
112 
113     if (!CI->use_empty())
114       CI->replaceAllUsesWith(NewCI);
115     CI->eraseFromParent();
116   }
117 
118   return true;
119 }
120 
121 static bool lowerIntrinsics(Module &M) {
122   bool Changed = false;
123   for (Function &F : M) {
124     if (F.getName().startswith("llvm.load.relative.")) {
125       Changed |= lowerLoadRelative(F);
126       continue;
127     }
128     switch (F.getIntrinsicID()) {
129     default:
130       break;
131     case Intrinsic::objc_autorelease:
132       Changed |= lowerObjCCall(F, "objc_autorelease");
133       break;
134     case Intrinsic::objc_autoreleasePoolPop:
135       Changed |= lowerObjCCall(F, "objc_autoreleasePoolPop");
136       break;
137     case Intrinsic::objc_autoreleasePoolPush:
138       Changed |= lowerObjCCall(F, "objc_autoreleasePoolPush");
139       break;
140     case Intrinsic::objc_autoreleaseReturnValue:
141       Changed |= lowerObjCCall(F, "objc_autoreleaseReturnValue");
142       break;
143     case Intrinsic::objc_copyWeak:
144       Changed |= lowerObjCCall(F, "objc_copyWeak");
145       break;
146     case Intrinsic::objc_destroyWeak:
147       Changed |= lowerObjCCall(F, "objc_destroyWeak");
148       break;
149     case Intrinsic::objc_initWeak:
150       Changed |= lowerObjCCall(F, "objc_initWeak");
151       break;
152     case Intrinsic::objc_loadWeak:
153       Changed |= lowerObjCCall(F, "objc_loadWeak");
154       break;
155     case Intrinsic::objc_loadWeakRetained:
156       Changed |= lowerObjCCall(F, "objc_loadWeakRetained");
157       break;
158     case Intrinsic::objc_moveWeak:
159       Changed |= lowerObjCCall(F, "objc_moveWeak");
160       break;
161     case Intrinsic::objc_release:
162       Changed |= lowerObjCCall(F, "objc_release", true);
163       break;
164     case Intrinsic::objc_retain:
165       Changed |= lowerObjCCall(F, "objc_retain", true);
166       break;
167     case Intrinsic::objc_retainAutorelease:
168       Changed |= lowerObjCCall(F, "objc_retainAutorelease");
169       break;
170     case Intrinsic::objc_retainAutoreleaseReturnValue:
171       Changed |= lowerObjCCall(F, "objc_retainAutoreleaseReturnValue");
172       break;
173     case Intrinsic::objc_retainAutoreleasedReturnValue:
174       Changed |= lowerObjCCall(F, "objc_retainAutoreleasedReturnValue");
175       break;
176     case Intrinsic::objc_retainBlock:
177       Changed |= lowerObjCCall(F, "objc_retainBlock");
178       break;
179     case Intrinsic::objc_storeStrong:
180       Changed |= lowerObjCCall(F, "objc_storeStrong");
181       break;
182     case Intrinsic::objc_storeWeak:
183       Changed |= lowerObjCCall(F, "objc_storeWeak");
184       break;
185     case Intrinsic::objc_unsafeClaimAutoreleasedReturnValue:
186       Changed |= lowerObjCCall(F, "objc_unsafeClaimAutoreleasedReturnValue");
187       break;
188     case Intrinsic::objc_retainedObject:
189       Changed |= lowerObjCCall(F, "objc_retainedObject");
190       break;
191     case Intrinsic::objc_unretainedObject:
192       Changed |= lowerObjCCall(F, "objc_unretainedObject");
193       break;
194     case Intrinsic::objc_unretainedPointer:
195       Changed |= lowerObjCCall(F, "objc_unretainedPointer");
196       break;
197     case Intrinsic::objc_retain_autorelease:
198       Changed |= lowerObjCCall(F, "objc_retain_autorelease");
199       break;
200     case Intrinsic::objc_sync_enter:
201       Changed |= lowerObjCCall(F, "objc_sync_enter");
202       break;
203     case Intrinsic::objc_sync_exit:
204       Changed |= lowerObjCCall(F, "objc_sync_exit");
205       break;
206     }
207   }
208   return Changed;
209 }
210 
211 namespace {
212 
213 class PreISelIntrinsicLoweringLegacyPass : public ModulePass {
214 public:
215   static char ID;
216 
217   PreISelIntrinsicLoweringLegacyPass() : ModulePass(ID) {}
218 
219   bool runOnModule(Module &M) override { return lowerIntrinsics(M); }
220 };
221 
222 } // end anonymous namespace
223 
224 char PreISelIntrinsicLoweringLegacyPass::ID;
225 
226 INITIALIZE_PASS(PreISelIntrinsicLoweringLegacyPass,
227                 "pre-isel-intrinsic-lowering", "Pre-ISel Intrinsic Lowering",
228                 false, false)
229 
230 ModulePass *llvm::createPreISelIntrinsicLoweringPass() {
231   return new PreISelIntrinsicLoweringLegacyPass;
232 }
233 
234 PreservedAnalyses PreISelIntrinsicLoweringPass::run(Module &M,
235                                                     ModuleAnalysisManager &AM) {
236   if (!lowerIntrinsics(M))
237     return PreservedAnalyses::all();
238   else
239     return PreservedAnalyses::none();
240 }
241