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 "llvm/CodeGen/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/Analysis/DebugInfo.h"
24 #include "llvm/CodeGen/Analysis.h"
25 #include "llvm/CodeGen/MachineFunction.h"
26 #include "llvm/CodeGen/MachineFrameInfo.h"
27 #include "llvm/CodeGen/MachineInstrBuilder.h"
28 #include "llvm/CodeGen/MachineModuleInfo.h"
29 #include "llvm/CodeGen/MachineRegisterInfo.h"
30 #include "llvm/Target/TargetRegisterInfo.h"
31 #include "llvm/Target/TargetData.h"
32 #include "llvm/Target/TargetInstrInfo.h"
33 #include "llvm/Target/TargetLowering.h"
34 #include "llvm/Target/TargetOptions.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/MathExtras.h"
38 #include <algorithm>
39 using namespace llvm;
40
41 /// isUsedOutsideOfDefiningBlock - Return true if this instruction is used by
42 /// PHI nodes or outside of the basic block that defines it, or used by a
43 /// switch or atomic instruction, which may expand to multiple basic blocks.
isUsedOutsideOfDefiningBlock(const Instruction * I)44 static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
45 if (I->use_empty()) return false;
46 if (isa<PHINode>(I)) return true;
47 const BasicBlock *BB = I->getParent();
48 for (Value::const_use_iterator UI = I->use_begin(), E = I->use_end();
49 UI != E; ++UI) {
50 const User *U = *UI;
51 if (cast<Instruction>(U)->getParent() != BB || isa<PHINode>(U))
52 return true;
53 }
54 return false;
55 }
56
FunctionLoweringInfo(const TargetLowering & tli)57 FunctionLoweringInfo::FunctionLoweringInfo(const TargetLowering &tli)
58 : TLI(tli) {
59 }
60
set(const Function & fn,MachineFunction & mf)61 void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
62 Fn = &fn;
63 MF = &mf;
64 RegInfo = &MF->getRegInfo();
65
66 // Check whether the function can return without sret-demotion.
67 SmallVector<ISD::OutputArg, 4> Outs;
68 GetReturnInfo(Fn->getReturnType(),
69 Fn->getAttributes().getRetAttributes(), Outs, TLI);
70 CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), *MF,
71 Fn->isVarArg(),
72 Outs, Fn->getContext());
73
74 // Initialize the mapping of values to registers. This is only set up for
75 // instruction values that are used outside of the block that defines
76 // them.
77 Function::const_iterator BB = Fn->begin(), EB = Fn->end();
78 for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
79 if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
80 if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
81 Type *Ty = AI->getAllocatedType();
82 uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
83 unsigned Align =
84 std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
85 AI->getAlignment());
86
87 TySize *= CUI->getZExtValue(); // Get total allocated size.
88 if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
89
90 // The object may need to be placed onto the stack near the stack
91 // protector if one exists. Determine here if this object is a suitable
92 // candidate. I.e., it would trigger the creation of a stack protector.
93 bool MayNeedSP =
94 (AI->isArrayAllocation() ||
95 (TySize > 8 && isa<ArrayType>(Ty) &&
96 cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
97 StaticAllocaMap[AI] =
98 MF->getFrameInfo()->CreateStackObject(TySize, Align, false, MayNeedSP);
99 }
100
101 for (; BB != EB; ++BB)
102 for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
103 // Mark values used outside their block as exported, by allocating
104 // a virtual register for them.
105 if (isUsedOutsideOfDefiningBlock(I))
106 if (!isa<AllocaInst>(I) ||
107 !StaticAllocaMap.count(cast<AllocaInst>(I)))
108 InitializeRegForValue(I);
109
110 // Collect llvm.dbg.declare information. This is done now instead of
111 // during the initial isel pass through the IR so that it is done
112 // in a predictable order.
113 if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
114 MachineModuleInfo &MMI = MF->getMMI();
115 if (MMI.hasDebugInfo() &&
116 DIVariable(DI->getVariable()).Verify() &&
117 !DI->getDebugLoc().isUnknown()) {
118 // Don't handle byval struct arguments or VLAs, for example.
119 // Non-byval arguments are handled here (they refer to the stack
120 // temporary alloca at this point).
121 const Value *Address = DI->getAddress();
122 if (Address) {
123 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
124 Address = BCI->getOperand(0);
125 if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
126 DenseMap<const AllocaInst *, int>::iterator SI =
127 StaticAllocaMap.find(AI);
128 if (SI != StaticAllocaMap.end()) { // Check for VLAs.
129 int FI = SI->second;
130 MMI.setVariableDbgInfo(DI->getVariable(),
131 FI, DI->getDebugLoc());
132 }
133 }
134 }
135 }
136 }
137 }
138
139 // Create an initial MachineBasicBlock for each LLVM BasicBlock in F. This
140 // also creates the initial PHI MachineInstrs, though none of the input
141 // operands are populated.
142 for (BB = Fn->begin(); BB != EB; ++BB) {
143 MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
144 MBBMap[BB] = MBB;
145 MF->push_back(MBB);
146
147 // Transfer the address-taken flag. This is necessary because there could
148 // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
149 // the first one should be marked.
150 if (BB->hasAddressTaken())
151 MBB->setHasAddressTaken();
152
153 // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
154 // appropriate.
155 for (BasicBlock::const_iterator I = BB->begin();
156 const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
157 if (PN->use_empty()) continue;
158
159 // Skip empty types
160 if (PN->getType()->isEmptyTy())
161 continue;
162
163 DebugLoc DL = PN->getDebugLoc();
164 unsigned PHIReg = ValueMap[PN];
165 assert(PHIReg && "PHI node does not have an assigned virtual register!");
166
167 SmallVector<EVT, 4> ValueVTs;
168 ComputeValueVTs(TLI, PN->getType(), ValueVTs);
169 for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
170 EVT VT = ValueVTs[vti];
171 unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
172 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
173 for (unsigned i = 0; i != NumRegisters; ++i)
174 BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
175 PHIReg += NumRegisters;
176 }
177 }
178 }
179
180 // Mark landing pad blocks.
181 for (BB = Fn->begin(); BB != EB; ++BB)
182 if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
183 MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
184 }
185
186 /// clear - Clear out all the function-specific state. This returns this
187 /// FunctionLoweringInfo to an empty state, ready to be used for a
188 /// different function.
clear()189 void FunctionLoweringInfo::clear() {
190 assert(CatchInfoFound.size() == CatchInfoLost.size() &&
191 "Not all catch info was assigned to a landing pad!");
192
193 MBBMap.clear();
194 ValueMap.clear();
195 StaticAllocaMap.clear();
196 #ifndef NDEBUG
197 CatchInfoLost.clear();
198 CatchInfoFound.clear();
199 #endif
200 LiveOutRegInfo.clear();
201 VisitedBBs.clear();
202 ArgDbgValues.clear();
203 ByValArgFrameIndexMap.clear();
204 RegFixups.clear();
205 }
206
207 /// CreateReg - Allocate a single virtual register for the given type.
CreateReg(EVT VT)208 unsigned FunctionLoweringInfo::CreateReg(EVT VT) {
209 return RegInfo->createVirtualRegister(TLI.getRegClassFor(VT));
210 }
211
212 /// CreateRegs - Allocate the appropriate number of virtual registers of
213 /// the correctly promoted or expanded types. Assign these registers
214 /// consecutive vreg numbers and return the first assigned number.
215 ///
216 /// In the case that the given value has struct or array type, this function
217 /// will assign registers for each member or element.
218 ///
CreateRegs(Type * Ty)219 unsigned FunctionLoweringInfo::CreateRegs(Type *Ty) {
220 SmallVector<EVT, 4> ValueVTs;
221 ComputeValueVTs(TLI, Ty, ValueVTs);
222
223 unsigned FirstReg = 0;
224 for (unsigned Value = 0, e = ValueVTs.size(); Value != e; ++Value) {
225 EVT ValueVT = ValueVTs[Value];
226 EVT RegisterVT = TLI.getRegisterType(Ty->getContext(), ValueVT);
227
228 unsigned NumRegs = TLI.getNumRegisters(Ty->getContext(), ValueVT);
229 for (unsigned i = 0; i != NumRegs; ++i) {
230 unsigned R = CreateReg(RegisterVT);
231 if (!FirstReg) FirstReg = R;
232 }
233 }
234 return FirstReg;
235 }
236
237 /// GetLiveOutRegInfo - Gets LiveOutInfo for a register, returning NULL if the
238 /// register is a PHI destination and the PHI's LiveOutInfo is not valid. If
239 /// the register's LiveOutInfo is for a smaller bit width, it is extended to
240 /// the larger bit width by zero extension. The bit width must be no smaller
241 /// than the LiveOutInfo's existing bit width.
242 const FunctionLoweringInfo::LiveOutInfo *
GetLiveOutRegInfo(unsigned Reg,unsigned BitWidth)243 FunctionLoweringInfo::GetLiveOutRegInfo(unsigned Reg, unsigned BitWidth) {
244 if (!LiveOutRegInfo.inBounds(Reg))
245 return NULL;
246
247 LiveOutInfo *LOI = &LiveOutRegInfo[Reg];
248 if (!LOI->IsValid)
249 return NULL;
250
251 if (BitWidth > LOI->KnownZero.getBitWidth()) {
252 LOI->NumSignBits = 1;
253 LOI->KnownZero = LOI->KnownZero.zextOrTrunc(BitWidth);
254 LOI->KnownOne = LOI->KnownOne.zextOrTrunc(BitWidth);
255 }
256
257 return LOI;
258 }
259
260 /// ComputePHILiveOutRegInfo - Compute LiveOutInfo for a PHI's destination
261 /// register based on the LiveOutInfo of its operands.
ComputePHILiveOutRegInfo(const PHINode * PN)262 void FunctionLoweringInfo::ComputePHILiveOutRegInfo(const PHINode *PN) {
263 Type *Ty = PN->getType();
264 if (!Ty->isIntegerTy() || Ty->isVectorTy())
265 return;
266
267 SmallVector<EVT, 1> ValueVTs;
268 ComputeValueVTs(TLI, Ty, ValueVTs);
269 assert(ValueVTs.size() == 1 &&
270 "PHIs with non-vector integer types should have a single VT.");
271 EVT IntVT = ValueVTs[0];
272
273 if (TLI.getNumRegisters(PN->getContext(), IntVT) != 1)
274 return;
275 IntVT = TLI.getTypeToTransformTo(PN->getContext(), IntVT);
276 unsigned BitWidth = IntVT.getSizeInBits();
277
278 unsigned DestReg = ValueMap[PN];
279 if (!TargetRegisterInfo::isVirtualRegister(DestReg))
280 return;
281 LiveOutRegInfo.grow(DestReg);
282 LiveOutInfo &DestLOI = LiveOutRegInfo[DestReg];
283
284 Value *V = PN->getIncomingValue(0);
285 if (isa<UndefValue>(V) || isa<ConstantExpr>(V)) {
286 DestLOI.NumSignBits = 1;
287 APInt Zero(BitWidth, 0);
288 DestLOI.KnownZero = Zero;
289 DestLOI.KnownOne = Zero;
290 return;
291 }
292
293 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
294 APInt Val = CI->getValue().zextOrTrunc(BitWidth);
295 DestLOI.NumSignBits = Val.getNumSignBits();
296 DestLOI.KnownZero = ~Val;
297 DestLOI.KnownOne = Val;
298 } else {
299 assert(ValueMap.count(V) && "V should have been placed in ValueMap when its"
300 "CopyToReg node was created.");
301 unsigned SrcReg = ValueMap[V];
302 if (!TargetRegisterInfo::isVirtualRegister(SrcReg)) {
303 DestLOI.IsValid = false;
304 return;
305 }
306 const LiveOutInfo *SrcLOI = GetLiveOutRegInfo(SrcReg, BitWidth);
307 if (!SrcLOI) {
308 DestLOI.IsValid = false;
309 return;
310 }
311 DestLOI = *SrcLOI;
312 }
313
314 assert(DestLOI.KnownZero.getBitWidth() == BitWidth &&
315 DestLOI.KnownOne.getBitWidth() == BitWidth &&
316 "Masks should have the same bit width as the type.");
317
318 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
319 Value *V = PN->getIncomingValue(i);
320 if (isa<UndefValue>(V) || isa<ConstantExpr>(V)) {
321 DestLOI.NumSignBits = 1;
322 APInt Zero(BitWidth, 0);
323 DestLOI.KnownZero = Zero;
324 DestLOI.KnownOne = Zero;
325 return;
326 }
327
328 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
329 APInt Val = CI->getValue().zextOrTrunc(BitWidth);
330 DestLOI.NumSignBits = std::min(DestLOI.NumSignBits, Val.getNumSignBits());
331 DestLOI.KnownZero &= ~Val;
332 DestLOI.KnownOne &= Val;
333 continue;
334 }
335
336 assert(ValueMap.count(V) && "V should have been placed in ValueMap when "
337 "its CopyToReg node was created.");
338 unsigned SrcReg = ValueMap[V];
339 if (!TargetRegisterInfo::isVirtualRegister(SrcReg)) {
340 DestLOI.IsValid = false;
341 return;
342 }
343 const LiveOutInfo *SrcLOI = GetLiveOutRegInfo(SrcReg, BitWidth);
344 if (!SrcLOI) {
345 DestLOI.IsValid = false;
346 return;
347 }
348 DestLOI.NumSignBits = std::min(DestLOI.NumSignBits, SrcLOI->NumSignBits);
349 DestLOI.KnownZero &= SrcLOI->KnownZero;
350 DestLOI.KnownOne &= SrcLOI->KnownOne;
351 }
352 }
353
354 /// setArgumentFrameIndex - Record frame index for the byval
355 /// argument. This overrides previous frame index entry for this argument,
356 /// if any.
setArgumentFrameIndex(const Argument * A,int FI)357 void FunctionLoweringInfo::setArgumentFrameIndex(const Argument *A,
358 int FI) {
359 ByValArgFrameIndexMap[A] = FI;
360 }
361
362 /// getArgumentFrameIndex - Get frame index for the byval argument.
363 /// If the argument does not have any assigned frame index then 0 is
364 /// returned.
getArgumentFrameIndex(const Argument * A)365 int FunctionLoweringInfo::getArgumentFrameIndex(const Argument *A) {
366 DenseMap<const Argument *, int>::iterator I =
367 ByValArgFrameIndexMap.find(A);
368 if (I != ByValArgFrameIndexMap.end())
369 return I->second;
370 DEBUG(dbgs() << "Argument does not have assigned frame index!");
371 return 0;
372 }
373
374 /// AddCatchInfo - Extract the personality and type infos from an eh.selector
375 /// call, and add them to the specified machine basic block.
AddCatchInfo(const CallInst & I,MachineModuleInfo * MMI,MachineBasicBlock * MBB)376 void llvm::AddCatchInfo(const CallInst &I, MachineModuleInfo *MMI,
377 MachineBasicBlock *MBB) {
378 // Inform the MachineModuleInfo of the personality for this landing pad.
379 const ConstantExpr *CE = cast<ConstantExpr>(I.getArgOperand(1));
380 assert(CE->getOpcode() == Instruction::BitCast &&
381 isa<Function>(CE->getOperand(0)) &&
382 "Personality should be a function");
383 MMI->addPersonality(MBB, cast<Function>(CE->getOperand(0)));
384
385 // Gather all the type infos for this landing pad and pass them along to
386 // MachineModuleInfo.
387 std::vector<const GlobalVariable *> TyInfo;
388 unsigned N = I.getNumArgOperands();
389
390 for (unsigned i = N - 1; i > 1; --i) {
391 if (const ConstantInt *CI = dyn_cast<ConstantInt>(I.getArgOperand(i))) {
392 unsigned FilterLength = CI->getZExtValue();
393 unsigned FirstCatch = i + FilterLength + !FilterLength;
394 assert(FirstCatch <= N && "Invalid filter length");
395
396 if (FirstCatch < N) {
397 TyInfo.reserve(N - FirstCatch);
398 for (unsigned j = FirstCatch; j < N; ++j)
399 TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
400 MMI->addCatchTypeInfo(MBB, TyInfo);
401 TyInfo.clear();
402 }
403
404 if (!FilterLength) {
405 // Cleanup.
406 MMI->addCleanup(MBB);
407 } else {
408 // Filter.
409 TyInfo.reserve(FilterLength - 1);
410 for (unsigned j = i + 1; j < FirstCatch; ++j)
411 TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
412 MMI->addFilterTypeInfo(MBB, TyInfo);
413 TyInfo.clear();
414 }
415
416 N = i;
417 }
418 }
419
420 if (N > 2) {
421 TyInfo.reserve(N - 2);
422 for (unsigned j = 2; j < N; ++j)
423 TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
424 MMI->addCatchTypeInfo(MBB, TyInfo);
425 }
426 }
427
CopyCatchInfo(const BasicBlock * SuccBB,const BasicBlock * LPad,MachineModuleInfo * MMI,FunctionLoweringInfo & FLI)428 void llvm::CopyCatchInfo(const BasicBlock *SuccBB, const BasicBlock *LPad,
429 MachineModuleInfo *MMI, FunctionLoweringInfo &FLI) {
430 SmallPtrSet<const BasicBlock*, 4> Visited;
431
432 // The 'eh.selector' call may not be in the direct successor of a basic block,
433 // but could be several successors deeper. If we don't find it, try going one
434 // level further. <rdar://problem/8824861>
435 while (Visited.insert(SuccBB)) {
436 for (BasicBlock::const_iterator I = SuccBB->begin(), E = --SuccBB->end();
437 I != E; ++I)
438 if (const EHSelectorInst *EHSel = dyn_cast<EHSelectorInst>(I)) {
439 // Apply the catch info to LPad.
440 AddCatchInfo(*EHSel, MMI, FLI.MBBMap[LPad]);
441 #ifndef NDEBUG
442 if (!FLI.MBBMap[SuccBB]->isLandingPad())
443 FLI.CatchInfoFound.insert(EHSel);
444 #endif
445 return;
446 }
447
448 const BranchInst *Br = dyn_cast<BranchInst>(SuccBB->getTerminator());
449 if (Br && Br->isUnconditional())
450 SuccBB = Br->getSuccessor(0);
451 else
452 break;
453 }
454 }
455
456 /// AddLandingPadInfo - Extract the exception handling information from the
457 /// landingpad instruction and add them to the specified machine module info.
AddLandingPadInfo(const LandingPadInst & I,MachineModuleInfo & MMI,MachineBasicBlock * MBB)458 void llvm::AddLandingPadInfo(const LandingPadInst &I, MachineModuleInfo &MMI,
459 MachineBasicBlock *MBB) {
460 MMI.addPersonality(MBB,
461 cast<Function>(I.getPersonalityFn()->stripPointerCasts()));
462
463 if (I.isCleanup())
464 MMI.addCleanup(MBB);
465
466 // FIXME: New EH - Add the clauses in reverse order. This isn't 100% correct,
467 // but we need to do it this way because of how the DWARF EH emitter
468 // processes the clauses.
469 for (unsigned i = I.getNumClauses(); i != 0; --i) {
470 Value *Val = I.getClause(i - 1);
471 if (I.isCatch(i - 1)) {
472 MMI.addCatchTypeInfo(MBB,
473 dyn_cast<GlobalVariable>(Val->stripPointerCasts()));
474 } else {
475 // Add filters in a list.
476 Constant *CVal = cast<Constant>(Val);
477 SmallVector<const GlobalVariable*, 4> FilterList;
478 for (User::op_iterator
479 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II)
480 FilterList.push_back(cast<GlobalVariable>((*II)->stripPointerCasts()));
481
482 MMI.addFilterTypeInfo(MBB, FilterList);
483 }
484 }
485 }
486