1 //===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines several CodeGen-specific LLVM IR analysis utilties.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/Analysis.h"
15 #include "llvm/Analysis/ValueTracking.h"
16 #include "llvm/DerivedTypes.h"
17 #include "llvm/Function.h"
18 #include "llvm/Instructions.h"
19 #include "llvm/IntrinsicInst.h"
20 #include "llvm/LLVMContext.h"
21 #include "llvm/Module.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/SelectionDAG.h"
24 #include "llvm/Target/TargetData.h"
25 #include "llvm/Target/TargetLowering.h"
26 #include "llvm/Target/TargetOptions.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/MathExtras.h"
31 /// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
32 /// of insertvalue or extractvalue indices that identify a member, return
33 /// the linearized index of the start of the member.
35 unsigned llvm::ComputeLinearIndex(Type *Ty,
36 const unsigned *Indices,
37 const unsigned *IndicesEnd,
39 // Base case: We're done.
40 if (Indices && Indices == IndicesEnd)
43 // Given a struct type, recursively traverse the elements.
44 if (StructType *STy = dyn_cast<StructType>(Ty)) {
45 for (StructType::element_iterator EB = STy->element_begin(),
47 EE = STy->element_end();
49 if (Indices && *Indices == unsigned(EI - EB))
50 return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
51 CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
55 // Given an array type, recursively traverse the elements.
56 else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
57 Type *EltTy = ATy->getElementType();
58 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
59 if (Indices && *Indices == i)
60 return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
61 CurIndex = ComputeLinearIndex(EltTy, 0, 0, CurIndex);
65 // We haven't found the type we're looking for, so keep searching.
69 /// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
70 /// EVTs that represent all the individual underlying
71 /// non-aggregate types that comprise it.
73 /// If Offsets is non-null, it points to a vector to be filled in
74 /// with the in-memory offsets of each of the individual values.
76 void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
77 SmallVectorImpl<EVT> &ValueVTs,
78 SmallVectorImpl<uint64_t> *Offsets,
79 uint64_t StartingOffset) {
80 // Given a struct type, recursively traverse the elements.
81 if (StructType *STy = dyn_cast<StructType>(Ty)) {
82 const StructLayout *SL = TLI.getTargetData()->getStructLayout(STy);
83 for (StructType::element_iterator EB = STy->element_begin(),
85 EE = STy->element_end();
87 ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
88 StartingOffset + SL->getElementOffset(EI - EB));
91 // Given an array type, recursively traverse the elements.
92 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
93 Type *EltTy = ATy->getElementType();
94 uint64_t EltSize = TLI.getTargetData()->getTypeAllocSize(EltTy);
95 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
96 ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
97 StartingOffset + i * EltSize);
100 // Interpret void as zero return values.
103 // Base case: we can get an EVT for this LLVM IR type.
104 ValueVTs.push_back(TLI.getValueType(Ty));
106 Offsets->push_back(StartingOffset);
109 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
110 GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
111 V = V->stripPointerCasts();
112 GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
114 if (GV && GV->getName() == "llvm.eh.catch.all.value") {
115 assert(GV->hasInitializer() &&
116 "The EH catch-all value must have an initializer");
117 Value *Init = GV->getInitializer();
118 GV = dyn_cast<GlobalVariable>(Init);
119 if (!GV) V = cast<ConstantPointerNull>(Init);
122 assert((GV || isa<ConstantPointerNull>(V)) &&
123 "TypeInfo must be a global variable or NULL");
127 /// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
128 /// processed uses a memory 'm' constraint.
130 llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
131 const TargetLowering &TLI) {
132 for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
133 InlineAsm::ConstraintInfo &CI = CInfos[i];
134 for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
135 TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
136 if (CType == TargetLowering::C_Memory)
140 // Indirect operand accesses access memory.
148 /// getFCmpCondCode - Return the ISD condition code corresponding to
149 /// the given LLVM IR floating-point condition code. This includes
150 /// consideration of global floating-point math flags.
152 ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
154 case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
155 case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
156 case FCmpInst::FCMP_OGT: return ISD::SETOGT;
157 case FCmpInst::FCMP_OGE: return ISD::SETOGE;
158 case FCmpInst::FCMP_OLT: return ISD::SETOLT;
159 case FCmpInst::FCMP_OLE: return ISD::SETOLE;
160 case FCmpInst::FCMP_ONE: return ISD::SETONE;
161 case FCmpInst::FCMP_ORD: return ISD::SETO;
162 case FCmpInst::FCMP_UNO: return ISD::SETUO;
163 case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
164 case FCmpInst::FCMP_UGT: return ISD::SETUGT;
165 case FCmpInst::FCMP_UGE: return ISD::SETUGE;
166 case FCmpInst::FCMP_ULT: return ISD::SETULT;
167 case FCmpInst::FCMP_ULE: return ISD::SETULE;
168 case FCmpInst::FCMP_UNE: return ISD::SETUNE;
169 case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
170 default: llvm_unreachable("Invalid FCmp predicate opcode!");
174 ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
176 case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
177 case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
178 case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
179 case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
180 case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
181 case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
186 /// getICmpCondCode - Return the ISD condition code corresponding to
187 /// the given LLVM IR integer condition code.
189 ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
191 case ICmpInst::ICMP_EQ: return ISD::SETEQ;
192 case ICmpInst::ICMP_NE: return ISD::SETNE;
193 case ICmpInst::ICMP_SLE: return ISD::SETLE;
194 case ICmpInst::ICMP_ULE: return ISD::SETULE;
195 case ICmpInst::ICMP_SGE: return ISD::SETGE;
196 case ICmpInst::ICMP_UGE: return ISD::SETUGE;
197 case ICmpInst::ICMP_SLT: return ISD::SETLT;
198 case ICmpInst::ICMP_ULT: return ISD::SETULT;
199 case ICmpInst::ICMP_SGT: return ISD::SETGT;
200 case ICmpInst::ICMP_UGT: return ISD::SETUGT;
202 llvm_unreachable("Invalid ICmp predicate opcode!");
207 /// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
208 /// through it (and any transitive noop operands to it) and return its input
209 /// value. This is used to determine if a tail call can be formed.
211 static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
212 // If V is not an instruction, it can't be looked through.
213 const Instruction *I = dyn_cast<Instruction>(V);
214 if (I == 0 || !I->hasOneUse() || I->getNumOperands() == 0) return V;
216 Value *Op = I->getOperand(0);
218 // Look through truly no-op truncates.
219 if (isa<TruncInst>(I) &&
220 TLI.isTruncateFree(I->getOperand(0)->getType(), I->getType()))
221 return getNoopInput(I->getOperand(0), TLI);
223 // Look through truly no-op bitcasts.
224 if (isa<BitCastInst>(I)) {
225 // No type change at all.
226 if (Op->getType() == I->getType())
227 return getNoopInput(Op, TLI);
229 // Pointer to pointer cast.
230 if (Op->getType()->isPointerTy() && I->getType()->isPointerTy())
231 return getNoopInput(Op, TLI);
233 if (isa<VectorType>(Op->getType()) && isa<VectorType>(I->getType()) &&
234 TLI.isTypeLegal(EVT::getEVT(Op->getType())) &&
235 TLI.isTypeLegal(EVT::getEVT(I->getType())))
236 return getNoopInput(Op, TLI);
239 // Look through inttoptr.
240 if (isa<IntToPtrInst>(I) && !isa<VectorType>(I->getType())) {
241 // Make sure this isn't a truncating or extending cast. We could support
242 // this eventually, but don't bother for now.
243 if (TLI.getPointerTy().getSizeInBits() ==
244 cast<IntegerType>(Op->getType())->getBitWidth())
245 return getNoopInput(Op, TLI);
248 // Look through ptrtoint.
249 if (isa<PtrToIntInst>(I) && !isa<VectorType>(I->getType())) {
250 // Make sure this isn't a truncating or extending cast. We could support
251 // this eventually, but don't bother for now.
252 if (TLI.getPointerTy().getSizeInBits() ==
253 cast<IntegerType>(I->getType())->getBitWidth())
254 return getNoopInput(Op, TLI);
258 // Otherwise it's not something we can look through.
263 /// Test if the given instruction is in a position to be optimized
264 /// with a tail-call. This roughly means that it's in a block with
265 /// a return and there's nothing that needs to be scheduled
266 /// between it and the return.
268 /// This function only tests target-independent requirements.
269 bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
270 const TargetLowering &TLI) {
271 const Instruction *I = CS.getInstruction();
272 const BasicBlock *ExitBB = I->getParent();
273 const TerminatorInst *Term = ExitBB->getTerminator();
274 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
276 // The block must end in a return statement or unreachable.
278 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
279 // an unreachable, for now. The way tailcall optimization is currently
280 // implemented means it will add an epilogue followed by a jump. That is
281 // not profitable. Also, if the callee is a special function (e.g.
282 // longjmp on x86), it can end up causing miscompilation that has not
283 // been fully understood.
285 (!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
286 !isa<UnreachableInst>(Term)))
289 // If I will have a chain, make sure no other instruction that will have a
290 // chain interposes between I and the return.
291 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
292 !isSafeToSpeculativelyExecute(I))
293 for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
297 // Debug info intrinsics do not get in the way of tail call optimization.
298 if (isa<DbgInfoIntrinsic>(BBI))
300 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
301 !isSafeToSpeculativelyExecute(BBI))
305 // If the block ends with a void return or unreachable, it doesn't matter
306 // what the call's return type is.
307 if (!Ret || Ret->getNumOperands() == 0) return true;
309 // If the return value is undef, it doesn't matter what the call's
311 if (isa<UndefValue>(Ret->getOperand(0))) return true;
313 // Conservatively require the attributes of the call to match those of
314 // the return. Ignore noalias because it doesn't affect the call sequence.
315 const Function *F = ExitBB->getParent();
316 Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
317 if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
320 // It's not safe to eliminate the sign / zero extension of the return value.
321 if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
324 // Otherwise, make sure the unmodified return value of I is the return value.
325 // We handle two cases: multiple return values + scalars.
326 Value *RetVal = Ret->getOperand(0);
327 if (!isa<InsertValueInst>(RetVal) || !isa<StructType>(RetVal->getType()))
328 // Handle scalars first.
329 return getNoopInput(Ret->getOperand(0), TLI) == I;
331 // If this is an aggregate return, look through the insert/extract values and
332 // see if each is transparent.
333 for (unsigned i = 0, e =cast<StructType>(RetVal->getType())->getNumElements();
335 const Value *InScalar = FindInsertedValue(RetVal, i);
336 if (InScalar == 0) return false;
337 InScalar = getNoopInput(InScalar, TLI);
339 // If the scalar value being inserted is an extractvalue of the right index
340 // from the call, then everything is good.
341 const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(InScalar);
342 if (EVI == 0 || EVI->getOperand(0) != I || EVI->getNumIndices() != 1 ||
343 EVI->getIndices()[0] != i)
350 bool llvm::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,
351 SDValue &Chain, const TargetLowering &TLI) {
352 const Function *F = DAG.getMachineFunction().getFunction();
354 // Conservatively require the attributes of the call to match those of
355 // the return. Ignore noalias because it doesn't affect the call sequence.
356 Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
357 if (CallerRetAttr & ~Attribute::NoAlias)
360 // It's not safe to eliminate the sign / zero extension of the return value.
361 if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
364 // Check if the only use is a function return node.
365 return TLI.isUsedByReturnOnly(Node, Chain);