1 //===-- FunctionLoweringInfo.cpp ------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This implements routines for translating functions from LLVM IR into
11 // Machine IR.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #define DEBUG_TYPE "function-lowering-info"
16 #include "FunctionLoweringInfo.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Function.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/LLVMContext.h"
22 #include "llvm/Module.h"
23 #include "llvm/CodeGen/Analysis.h"
24 #include "llvm/CodeGen/MachineFunction.h"
25 #include "llvm/CodeGen/MachineFrameInfo.h"
26 #include "llvm/CodeGen/MachineInstrBuilder.h"
27 #include "llvm/CodeGen/MachineModuleInfo.h"
28 #include "llvm/CodeGen/MachineRegisterInfo.h"
29 #include "llvm/Target/TargetRegisterInfo.h"
30 #include "llvm/Target/TargetData.h"
31 #include "llvm/Target/TargetFrameInfo.h"
32 #include "llvm/Target/TargetInstrInfo.h"
33 #include "llvm/Target/TargetIntrinsicInfo.h"
34 #include "llvm/Target/TargetLowering.h"
35 #include "llvm/Target/TargetOptions.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/MathExtras.h"
39 #include <algorithm>
40 using namespace llvm;
41 
42 /// isUsedOutsideOfDefiningBlock - Return true if this instruction is used by
43 /// PHI nodes or outside of the basic block that defines it, or used by a
44 /// switch or atomic instruction, which may expand to multiple basic blocks.
45 static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
46   if (I->use_empty()) return false;
47   if (isa<PHINode>(I)) return true;
48   const BasicBlock *BB = I->getParent();
49   for (Value::const_use_iterator UI = I->use_begin(), E = I->use_end();
50         UI != E; ++UI)
51     if (cast<Instruction>(*UI)->getParent() != BB || isa<PHINode>(*UI))
52       return true;
53   return false;
54 }
55 
56 /// isOnlyUsedInEntryBlock - If the specified argument is only used in the
57 /// entry block, return true.  This includes arguments used by switches, since
58 /// the switch may expand into multiple basic blocks.
59 static bool isOnlyUsedInEntryBlock(const Argument *A, bool EnableFastISel) {
60   // With FastISel active, we may be splitting blocks, so force creation
61   // of virtual registers for all non-dead arguments.
62   if (EnableFastISel)
63     return A->use_empty();
64 
65   const BasicBlock *Entry = A->getParent()->begin();
66   for (Value::const_use_iterator UI = A->use_begin(), E = A->use_end();
67        UI != E; ++UI)
68     if (cast<Instruction>(*UI)->getParent() != Entry || isa<SwitchInst>(*UI))
69       return false;  // Use not in entry block.
70   return true;
71 }
72 
73 FunctionLoweringInfo::FunctionLoweringInfo(const TargetLowering &tli)
74   : TLI(tli) {
75 }
76 
77 void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
78   Fn = &fn;
79   MF = &mf;
80   RegInfo = &MF->getRegInfo();
81 
82   // Create a vreg for each argument register that is not dead and is used
83   // outside of the entry block for the function.
84   for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
85        AI != E; ++AI)
86     if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
87       InitializeRegForValue(AI);
88 
89   // Initialize the mapping of values to registers.  This is only set up for
90   // instruction values that are used outside of the block that defines
91   // them.
92   Function::const_iterator BB = Fn->begin(), EB = Fn->end();
93   for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
94     if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
95       if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
96         const Type *Ty = AI->getAllocatedType();
97         uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
98         unsigned Align =
99           std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
100                    AI->getAlignment());
101 
102         TySize *= CUI->getZExtValue();   // Get total allocated size.
103         if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
104         StaticAllocaMap[AI] =
105           MF->getFrameInfo()->CreateStackObject(TySize, Align, false);
106       }
107 
108   for (; BB != EB; ++BB)
109     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
110       if (isUsedOutsideOfDefiningBlock(I))
111         if (!isa<AllocaInst>(I) ||
112             !StaticAllocaMap.count(cast<AllocaInst>(I)))
113           InitializeRegForValue(I);
114 
115   // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
116   // also creates the initial PHI MachineInstrs, though none of the input
117   // operands are populated.
118   for (BB = Fn->begin(); BB != EB; ++BB) {
119     MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
120     MBBMap[BB] = MBB;
121     MF->push_back(MBB);
122 
123     // Transfer the address-taken flag. This is necessary because there could
124     // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
125     // the first one should be marked.
126     if (BB->hasAddressTaken())
127       MBB->setHasAddressTaken();
128 
129     // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
130     // appropriate.
131     for (BasicBlock::const_iterator I = BB->begin();
132          const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
133       if (PN->use_empty()) continue;
134 
135       DebugLoc DL = PN->getDebugLoc();
136       unsigned PHIReg = ValueMap[PN];
137       assert(PHIReg && "PHI node does not have an assigned virtual register!");
138 
139       SmallVector<EVT, 4> ValueVTs;
140       ComputeValueVTs(TLI, PN->getType(), ValueVTs);
141       for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
142         EVT VT = ValueVTs[vti];
143         unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
144         const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
145         for (unsigned i = 0; i != NumRegisters; ++i)
146           BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
147         PHIReg += NumRegisters;
148       }
149     }
150   }
151 
152   // Mark landing pad blocks.
153   for (BB = Fn->begin(); BB != EB; ++BB)
154     if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
155       MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
156 }
157 
158 /// clear - Clear out all the function-specific state. This returns this
159 /// FunctionLoweringInfo to an empty state, ready to be used for a
160 /// different function.
161 void FunctionLoweringInfo::clear() {
162   assert(CatchInfoFound.size() == CatchInfoLost.size() &&
163          "Not all catch info was assigned to a landing pad!");
164 
165   MBBMap.clear();
166   ValueMap.clear();
167   StaticAllocaMap.clear();
168 #ifndef NDEBUG
169   CatchInfoLost.clear();
170   CatchInfoFound.clear();
171 #endif
172   LiveOutRegInfo.clear();
173   ArgDbgValues.clear();
174 }
175 
176 unsigned FunctionLoweringInfo::MakeReg(EVT VT) {
177   return RegInfo->createVirtualRegister(TLI.getRegClassFor(VT));
178 }
179 
180 /// CreateRegForValue - Allocate the appropriate number of virtual registers of
181 /// the correctly promoted or expanded types.  Assign these registers
182 /// consecutive vreg numbers and return the first assigned number.
183 ///
184 /// In the case that the given value has struct or array type, this function
185 /// will assign registers for each member or element.
186 ///
187 unsigned FunctionLoweringInfo::CreateRegForValue(const Value *V) {
188   SmallVector<EVT, 4> ValueVTs;
189   ComputeValueVTs(TLI, V->getType(), ValueVTs);
190 
191   unsigned FirstReg = 0;
192   for (unsigned Value = 0, e = ValueVTs.size(); Value != e; ++Value) {
193     EVT ValueVT = ValueVTs[Value];
194     EVT RegisterVT = TLI.getRegisterType(V->getContext(), ValueVT);
195 
196     unsigned NumRegs = TLI.getNumRegisters(V->getContext(), ValueVT);
197     for (unsigned i = 0; i != NumRegs; ++i) {
198       unsigned R = MakeReg(RegisterVT);
199       if (!FirstReg) FirstReg = R;
200     }
201   }
202   return FirstReg;
203 }
204 
205 /// AddCatchInfo - Extract the personality and type infos from an eh.selector
206 /// call, and add them to the specified machine basic block.
207 void llvm::AddCatchInfo(const CallInst &I, MachineModuleInfo *MMI,
208                         MachineBasicBlock *MBB) {
209   // Inform the MachineModuleInfo of the personality for this landing pad.
210   const ConstantExpr *CE = cast<ConstantExpr>(I.getOperand(2));
211   assert(CE->getOpcode() == Instruction::BitCast &&
212          isa<Function>(CE->getOperand(0)) &&
213          "Personality should be a function");
214   MMI->addPersonality(MBB, cast<Function>(CE->getOperand(0)));
215 
216   // Gather all the type infos for this landing pad and pass them along to
217   // MachineModuleInfo.
218   std::vector<const GlobalVariable *> TyInfo;
219   unsigned N = I.getNumOperands();
220 
221   for (unsigned i = N - 1; i > 2; --i) {
222     if (const ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(i))) {
223       unsigned FilterLength = CI->getZExtValue();
224       unsigned FirstCatch = i + FilterLength + !FilterLength;
225       assert (FirstCatch <= N && "Invalid filter length");
226 
227       if (FirstCatch < N) {
228         TyInfo.reserve(N - FirstCatch);
229         for (unsigned j = FirstCatch; j < N; ++j)
230           TyInfo.push_back(ExtractTypeInfo(I.getOperand(j)));
231         MMI->addCatchTypeInfo(MBB, TyInfo);
232         TyInfo.clear();
233       }
234 
235       if (!FilterLength) {
236         // Cleanup.
237         MMI->addCleanup(MBB);
238       } else {
239         // Filter.
240         TyInfo.reserve(FilterLength - 1);
241         for (unsigned j = i + 1; j < FirstCatch; ++j)
242           TyInfo.push_back(ExtractTypeInfo(I.getOperand(j)));
243         MMI->addFilterTypeInfo(MBB, TyInfo);
244         TyInfo.clear();
245       }
246 
247       N = i;
248     }
249   }
250 
251   if (N > 3) {
252     TyInfo.reserve(N - 3);
253     for (unsigned j = 3; j < N; ++j)
254       TyInfo.push_back(ExtractTypeInfo(I.getOperand(j)));
255     MMI->addCatchTypeInfo(MBB, TyInfo);
256   }
257 }
258 
259 void llvm::CopyCatchInfo(const BasicBlock *SrcBB, const BasicBlock *DestBB,
260                          MachineModuleInfo *MMI, FunctionLoweringInfo &FLI) {
261   for (BasicBlock::const_iterator I = SrcBB->begin(), E = --SrcBB->end();
262        I != E; ++I)
263     if (const EHSelectorInst *EHSel = dyn_cast<EHSelectorInst>(I)) {
264       // Apply the catch info to DestBB.
265       AddCatchInfo(*EHSel, MMI, FLI.MBBMap[DestBB]);
266 #ifndef NDEBUG
267       if (!FLI.MBBMap[SrcBB]->isLandingPad())
268         FLI.CatchInfoFound.insert(EHSel);
269 #endif
270     }
271 }
272