1 //===-- GenericToNVVM.cpp - Convert generic module to NVVM module - 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 // Convert generic global variables into either .global or .const access based
10 // on the variable's "constant" qualifier.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "MCTargetDesc/NVPTXBaseInfo.h"
15 #include "NVPTX.h"
16 #include "NVPTXUtilities.h"
17 #include "llvm/CodeGen/ValueTypes.h"
18 #include "llvm/IR/Constants.h"
19 #include "llvm/IR/DerivedTypes.h"
20 #include "llvm/IR/IRBuilder.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/Intrinsics.h"
23 #include "llvm/IR/LegacyPassManager.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/IR/Operator.h"
26 #include "llvm/IR/ValueMap.h"
27 #include "llvm/Transforms/Utils/ValueMapper.h"
28 
29 using namespace llvm;
30 
31 namespace llvm {
32 void initializeGenericToNVVMPass(PassRegistry &);
33 }
34 
35 namespace {
36 class GenericToNVVM : public ModulePass {
37 public:
38   static char ID;
39 
40   GenericToNVVM() : ModulePass(ID) {}
41 
42   bool runOnModule(Module &M) override;
43 
44   void getAnalysisUsage(AnalysisUsage &AU) const override {}
45 
46 private:
47   Value *remapConstant(Module *M, Function *F, Constant *C,
48                        IRBuilder<> &Builder);
49   Value *remapConstantVectorOrConstantAggregate(Module *M, Function *F,
50                                                 Constant *C,
51                                                 IRBuilder<> &Builder);
52   Value *remapConstantExpr(Module *M, Function *F, ConstantExpr *C,
53                            IRBuilder<> &Builder);
54 
55   typedef ValueMap<GlobalVariable *, GlobalVariable *> GVMapTy;
56   typedef ValueMap<Constant *, Value *> ConstantToValueMapTy;
57   GVMapTy GVMap;
58   ConstantToValueMapTy ConstantToValueMap;
59 };
60 } // end namespace
61 
62 char GenericToNVVM::ID = 0;
63 
64 ModulePass *llvm::createGenericToNVVMPass() { return new GenericToNVVM(); }
65 
66 INITIALIZE_PASS(
67     GenericToNVVM, "generic-to-nvvm",
68     "Ensure that the global variables are in the global address space", false,
69     false)
70 
71 bool GenericToNVVM::runOnModule(Module &M) {
72   // Create a clone of each global variable that has the default address space.
73   // The clone is created with the global address space  specifier, and the pair
74   // of original global variable and its clone is placed in the GVMap for later
75   // use.
76 
77   for (GlobalVariable &GV : llvm::make_early_inc_range(M.globals())) {
78     if (GV.getType()->getAddressSpace() == llvm::ADDRESS_SPACE_GENERIC &&
79         !llvm::isTexture(GV) && !llvm::isSurface(GV) && !llvm::isSampler(GV) &&
80         !GV.getName().startswith("llvm.")) {
81       GlobalVariable *NewGV = new GlobalVariable(
82           M, GV.getValueType(), GV.isConstant(), GV.getLinkage(),
83           GV.hasInitializer() ? GV.getInitializer() : nullptr, "", &GV,
84           GV.getThreadLocalMode(), llvm::ADDRESS_SPACE_GLOBAL);
85       NewGV->copyAttributesFrom(&GV);
86       GVMap[&GV] = NewGV;
87     }
88   }
89 
90   // Return immediately, if every global variable has a specific address space
91   // specifier.
92   if (GVMap.empty()) {
93     return false;
94   }
95 
96   // Walk through the instructions in function defitinions, and replace any use
97   // of original global variables in GVMap with a use of the corresponding
98   // copies in GVMap.  If necessary, promote constants to instructions.
99   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
100     if (I->isDeclaration()) {
101       continue;
102     }
103     IRBuilder<> Builder(I->getEntryBlock().getFirstNonPHIOrDbg());
104     for (Function::iterator BBI = I->begin(), BBE = I->end(); BBI != BBE;
105          ++BBI) {
106       for (BasicBlock::iterator II = BBI->begin(), IE = BBI->end(); II != IE;
107            ++II) {
108         for (unsigned i = 0, e = II->getNumOperands(); i < e; ++i) {
109           Value *Operand = II->getOperand(i);
110           if (isa<Constant>(Operand)) {
111             II->setOperand(
112                 i, remapConstant(&M, &*I, cast<Constant>(Operand), Builder));
113           }
114         }
115       }
116     }
117     ConstantToValueMap.clear();
118   }
119 
120   // Copy GVMap over to a standard value map.
121   ValueToValueMapTy VM;
122   for (auto I = GVMap.begin(), E = GVMap.end(); I != E; ++I)
123     VM[I->first] = I->second;
124 
125   // Walk through the global variable  initializers, and replace any use of
126   // original global variables in GVMap with a use of the corresponding copies
127   // in GVMap.  The copies need to be bitcast to the original global variable
128   // types, as we cannot use cvta in global variable initializers.
129   for (GVMapTy::iterator I = GVMap.begin(), E = GVMap.end(); I != E;) {
130     GlobalVariable *GV = I->first;
131     GlobalVariable *NewGV = I->second;
132 
133     // Remove GV from the map so that it can be RAUWed.  Note that
134     // DenseMap::erase() won't invalidate any iterators but this one.
135     auto Next = std::next(I);
136     GVMap.erase(I);
137     I = Next;
138 
139     Constant *BitCastNewGV = ConstantExpr::getPointerCast(NewGV, GV->getType());
140     // At this point, the remaining uses of GV should be found only in global
141     // variable initializers, as other uses have been already been removed
142     // while walking through the instructions in function definitions.
143     GV->replaceAllUsesWith(BitCastNewGV);
144     std::string Name = std::string(GV->getName());
145     GV->eraseFromParent();
146     NewGV->setName(Name);
147   }
148   assert(GVMap.empty() && "Expected it to be empty by now");
149 
150   return true;
151 }
152 
153 Value *GenericToNVVM::remapConstant(Module *M, Function *F, Constant *C,
154                                     IRBuilder<> &Builder) {
155   // If the constant C has been converted already in the given function  F, just
156   // return the converted value.
157   ConstantToValueMapTy::iterator CTII = ConstantToValueMap.find(C);
158   if (CTII != ConstantToValueMap.end()) {
159     return CTII->second;
160   }
161 
162   Value *NewValue = C;
163   if (isa<GlobalVariable>(C)) {
164     // If the constant C is a global variable and is found in GVMap, substitute
165     //
166     //   addrspacecast GVMap[C] to addrspace(0)
167     //
168     // for our use of C.
169     GVMapTy::iterator I = GVMap.find(cast<GlobalVariable>(C));
170     if (I != GVMap.end()) {
171       GlobalVariable *GV = I->second;
172       NewValue = Builder.CreateAddrSpaceCast(
173           GV,
174           PointerType::get(GV->getValueType(), llvm::ADDRESS_SPACE_GENERIC));
175     }
176   } else if (isa<ConstantAggregate>(C)) {
177     // If any element in the constant vector or aggregate C is or uses a global
178     // variable in GVMap, the constant C needs to be reconstructed, using a set
179     // of instructions.
180     NewValue = remapConstantVectorOrConstantAggregate(M, F, C, Builder);
181   } else if (isa<ConstantExpr>(C)) {
182     // If any operand in the constant expression C is or uses a global variable
183     // in GVMap, the constant expression C needs to be reconstructed, using a
184     // set of instructions.
185     NewValue = remapConstantExpr(M, F, cast<ConstantExpr>(C), Builder);
186   }
187 
188   ConstantToValueMap[C] = NewValue;
189   return NewValue;
190 }
191 
192 Value *GenericToNVVM::remapConstantVectorOrConstantAggregate(
193     Module *M, Function *F, Constant *C, IRBuilder<> &Builder) {
194   bool OperandChanged = false;
195   SmallVector<Value *, 4> NewOperands;
196   unsigned NumOperands = C->getNumOperands();
197 
198   // Check if any element is or uses a global variable in  GVMap, and thus
199   // converted to another value.
200   for (unsigned i = 0; i < NumOperands; ++i) {
201     Value *Operand = C->getOperand(i);
202     Value *NewOperand = remapConstant(M, F, cast<Constant>(Operand), Builder);
203     OperandChanged |= Operand != NewOperand;
204     NewOperands.push_back(NewOperand);
205   }
206 
207   // If none of the elements has been modified, return C as it is.
208   if (!OperandChanged) {
209     return C;
210   }
211 
212   // If any of the elements has been  modified, construct the equivalent
213   // vector or aggregate value with a set instructions and the converted
214   // elements.
215   Value *NewValue = PoisonValue::get(C->getType());
216   if (isa<ConstantVector>(C)) {
217     for (unsigned i = 0; i < NumOperands; ++i) {
218       Value *Idx = ConstantInt::get(Type::getInt32Ty(M->getContext()), i);
219       NewValue = Builder.CreateInsertElement(NewValue, NewOperands[i], Idx);
220     }
221   } else {
222     for (unsigned i = 0; i < NumOperands; ++i) {
223       NewValue =
224           Builder.CreateInsertValue(NewValue, NewOperands[i], makeArrayRef(i));
225     }
226   }
227 
228   return NewValue;
229 }
230 
231 Value *GenericToNVVM::remapConstantExpr(Module *M, Function *F, ConstantExpr *C,
232                                         IRBuilder<> &Builder) {
233   bool OperandChanged = false;
234   SmallVector<Value *, 4> NewOperands;
235   unsigned NumOperands = C->getNumOperands();
236 
237   // Check if any operand is or uses a global variable in  GVMap, and thus
238   // converted to another value.
239   for (unsigned i = 0; i < NumOperands; ++i) {
240     Value *Operand = C->getOperand(i);
241     Value *NewOperand = remapConstant(M, F, cast<Constant>(Operand), Builder);
242     OperandChanged |= Operand != NewOperand;
243     NewOperands.push_back(NewOperand);
244   }
245 
246   // If none of the operands has been modified, return C as it is.
247   if (!OperandChanged) {
248     return C;
249   }
250 
251   // If any of the operands has been modified, construct the instruction with
252   // the converted operands.
253   unsigned Opcode = C->getOpcode();
254   switch (Opcode) {
255   case Instruction::ICmp:
256     // CompareConstantExpr (icmp)
257     return Builder.CreateICmp(CmpInst::Predicate(C->getPredicate()),
258                               NewOperands[0], NewOperands[1]);
259   case Instruction::FCmp:
260     // CompareConstantExpr (fcmp)
261     llvm_unreachable("Address space conversion should have no effect "
262                      "on float point CompareConstantExpr (fcmp)!");
263   case Instruction::ExtractElement:
264     // ExtractElementConstantExpr
265     return Builder.CreateExtractElement(NewOperands[0], NewOperands[1]);
266   case Instruction::InsertElement:
267     // InsertElementConstantExpr
268     return Builder.CreateInsertElement(NewOperands[0], NewOperands[1],
269                                        NewOperands[2]);
270   case Instruction::ShuffleVector:
271     // ShuffleVector
272     return Builder.CreateShuffleVector(NewOperands[0], NewOperands[1],
273                                        NewOperands[2]);
274   case Instruction::ExtractValue:
275     // ExtractValueConstantExpr
276     return Builder.CreateExtractValue(NewOperands[0], C->getIndices());
277   case Instruction::InsertValue:
278     // InsertValueConstantExpr
279     return Builder.CreateInsertValue(NewOperands[0], NewOperands[1],
280                                      C->getIndices());
281   case Instruction::GetElementPtr:
282     // GetElementPtrConstantExpr
283     return cast<GEPOperator>(C)->isInBounds()
284                ? Builder.CreateGEP(
285                      cast<GEPOperator>(C)->getSourceElementType(),
286                      NewOperands[0],
287                      makeArrayRef(&NewOperands[1], NumOperands - 1))
288                : Builder.CreateInBoundsGEP(
289                      cast<GEPOperator>(C)->getSourceElementType(),
290                      NewOperands[0],
291                      makeArrayRef(&NewOperands[1], NumOperands - 1));
292   case Instruction::Select:
293     // SelectConstantExpr
294     return Builder.CreateSelect(NewOperands[0], NewOperands[1], NewOperands[2]);
295   default:
296     // BinaryConstantExpr
297     if (Instruction::isBinaryOp(Opcode)) {
298       return Builder.CreateBinOp(Instruction::BinaryOps(C->getOpcode()),
299                                  NewOperands[0], NewOperands[1]);
300     }
301     // UnaryConstantExpr
302     if (Instruction::isCast(Opcode)) {
303       return Builder.CreateCast(Instruction::CastOps(C->getOpcode()),
304                                 NewOperands[0], C->getType());
305     }
306     llvm_unreachable("GenericToNVVM encountered an unsupported ConstantExpr");
307   }
308 }
309