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/CodeGen/MachineFunction.h"
17 #include "llvm/IR/DataLayout.h"
18 #include "llvm/IR/DerivedTypes.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/Instructions.h"
21 #include "llvm/IR/IntrinsicInst.h"
22 #include "llvm/IR/LLVMContext.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/MathExtras.h"
26 #include "llvm/Target/TargetLowering.h"
27 #include "llvm/Target/TargetOptions.h"
30 /// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
31 /// of insertvalue or extractvalue indices that identify a member, return
32 /// the linearized index of the start of the member.
34 unsigned llvm::ComputeLinearIndex(Type *Ty,
35 const unsigned *Indices,
36 const unsigned *IndicesEnd,
38 // Base case: We're done.
39 if (Indices && Indices == IndicesEnd)
42 // Given a struct type, recursively traverse the elements.
43 if (StructType *STy = dyn_cast<StructType>(Ty)) {
44 for (StructType::element_iterator EB = STy->element_begin(),
46 EE = STy->element_end();
48 if (Indices && *Indices == unsigned(EI - EB))
49 return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
50 CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
54 // Given an array type, recursively traverse the elements.
55 else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
56 Type *EltTy = ATy->getElementType();
57 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
58 if (Indices && *Indices == i)
59 return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
60 CurIndex = ComputeLinearIndex(EltTy, 0, 0, CurIndex);
64 // We haven't found the type we're looking for, so keep searching.
68 /// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
69 /// EVTs that represent all the individual underlying
70 /// non-aggregate types that comprise it.
72 /// If Offsets is non-null, it points to a vector to be filled in
73 /// with the in-memory offsets of each of the individual values.
75 void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
76 SmallVectorImpl<EVT> &ValueVTs,
77 SmallVectorImpl<uint64_t> *Offsets,
78 uint64_t StartingOffset) {
79 // Given a struct type, recursively traverse the elements.
80 if (StructType *STy = dyn_cast<StructType>(Ty)) {
81 const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
82 for (StructType::element_iterator EB = STy->element_begin(),
84 EE = STy->element_end();
86 ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
87 StartingOffset + SL->getElementOffset(EI - EB));
90 // Given an array type, recursively traverse the elements.
91 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
92 Type *EltTy = ATy->getElementType();
93 uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
94 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
95 ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
96 StartingOffset + i * EltSize);
99 // Interpret void as zero return values.
102 // Base case: we can get an EVT for this LLVM IR type.
103 ValueVTs.push_back(TLI.getValueType(Ty));
105 Offsets->push_back(StartingOffset);
108 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
109 GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
110 V = V->stripPointerCasts();
111 GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
113 if (GV && GV->getName() == "llvm.eh.catch.all.value") {
114 assert(GV->hasInitializer() &&
115 "The EH catch-all value must have an initializer");
116 Value *Init = GV->getInitializer();
117 GV = dyn_cast<GlobalVariable>(Init);
118 if (!GV) V = cast<ConstantPointerNull>(Init);
121 assert((GV || isa<ConstantPointerNull>(V)) &&
122 "TypeInfo must be a global variable or NULL");
126 /// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
127 /// processed uses a memory 'm' constraint.
129 llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
130 const TargetLowering &TLI) {
131 for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
132 InlineAsm::ConstraintInfo &CI = CInfos[i];
133 for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
134 TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
135 if (CType == TargetLowering::C_Memory)
139 // Indirect operand accesses access memory.
147 /// getFCmpCondCode - Return the ISD condition code corresponding to
148 /// the given LLVM IR floating-point condition code. This includes
149 /// consideration of global floating-point math flags.
151 ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
153 case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
154 case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
155 case FCmpInst::FCMP_OGT: return ISD::SETOGT;
156 case FCmpInst::FCMP_OGE: return ISD::SETOGE;
157 case FCmpInst::FCMP_OLT: return ISD::SETOLT;
158 case FCmpInst::FCMP_OLE: return ISD::SETOLE;
159 case FCmpInst::FCMP_ONE: return ISD::SETONE;
160 case FCmpInst::FCMP_ORD: return ISD::SETO;
161 case FCmpInst::FCMP_UNO: return ISD::SETUO;
162 case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
163 case FCmpInst::FCMP_UGT: return ISD::SETUGT;
164 case FCmpInst::FCMP_UGE: return ISD::SETUGE;
165 case FCmpInst::FCMP_ULT: return ISD::SETULT;
166 case FCmpInst::FCMP_ULE: return ISD::SETULE;
167 case FCmpInst::FCMP_UNE: return ISD::SETUNE;
168 case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
169 default: llvm_unreachable("Invalid FCmp predicate opcode!");
173 ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
175 case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
176 case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
177 case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
178 case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
179 case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
180 case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
185 /// getICmpCondCode - Return the ISD condition code corresponding to
186 /// the given LLVM IR integer condition code.
188 ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
190 case ICmpInst::ICMP_EQ: return ISD::SETEQ;
191 case ICmpInst::ICMP_NE: return ISD::SETNE;
192 case ICmpInst::ICMP_SLE: return ISD::SETLE;
193 case ICmpInst::ICMP_ULE: return ISD::SETULE;
194 case ICmpInst::ICMP_SGE: return ISD::SETGE;
195 case ICmpInst::ICMP_UGE: return ISD::SETUGE;
196 case ICmpInst::ICMP_SLT: return ISD::SETLT;
197 case ICmpInst::ICMP_ULT: return ISD::SETULT;
198 case ICmpInst::ICMP_SGT: return ISD::SETGT;
199 case ICmpInst::ICMP_UGT: return ISD::SETUGT;
201 llvm_unreachable("Invalid ICmp predicate opcode!");
206 /// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
207 /// through it (and any transitive noop operands to it) and return its input
208 /// value. This is used to determine if a tail call can be formed.
210 static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
211 // If V is not an instruction, it can't be looked through.
212 const Instruction *I = dyn_cast<Instruction>(V);
213 if (I == 0 || !I->hasOneUse() || I->getNumOperands() == 0) return V;
215 Value *Op = I->getOperand(0);
217 // Look through truly no-op truncates.
218 if (isa<TruncInst>(I) &&
219 TLI.isTruncateFree(I->getOperand(0)->getType(), I->getType()))
220 return getNoopInput(I->getOperand(0), TLI);
222 // Look through truly no-op bitcasts.
223 if (isa<BitCastInst>(I)) {
224 // No type change at all.
225 if (Op->getType() == I->getType())
226 return getNoopInput(Op, TLI);
228 // Pointer to pointer cast.
229 if (Op->getType()->isPointerTy() && I->getType()->isPointerTy())
230 return getNoopInput(Op, TLI);
232 if (isa<VectorType>(Op->getType()) && isa<VectorType>(I->getType()) &&
233 TLI.isTypeLegal(EVT::getEVT(Op->getType())) &&
234 TLI.isTypeLegal(EVT::getEVT(I->getType())))
235 return getNoopInput(Op, TLI);
238 // Look through inttoptr.
239 if (isa<IntToPtrInst>(I) && !isa<VectorType>(I->getType())) {
240 // Make sure this isn't a truncating or extending cast. We could support
241 // this eventually, but don't bother for now.
242 if (TLI.getPointerTy().getSizeInBits() ==
243 cast<IntegerType>(Op->getType())->getBitWidth())
244 return getNoopInput(Op, TLI);
247 // Look through ptrtoint.
248 if (isa<PtrToIntInst>(I) && !isa<VectorType>(I->getType())) {
249 // Make sure this isn't a truncating or extending cast. We could support
250 // this eventually, but don't bother for now.
251 if (TLI.getPointerTy().getSizeInBits() ==
252 cast<IntegerType>(I->getType())->getBitWidth())
253 return getNoopInput(Op, TLI);
257 // Otherwise it's not something we can look through.
262 /// Test if the given instruction is in a position to be optimized
263 /// with a tail-call. This roughly means that it's in a block with
264 /// a return and there's nothing that needs to be scheduled
265 /// between it and the return.
267 /// This function only tests target-independent requirements.
268 bool llvm::isInTailCallPosition(ImmutableCallSite CS,const TargetLowering &TLI){
269 const Instruction *I = CS.getInstruction();
270 const BasicBlock *ExitBB = I->getParent();
271 const TerminatorInst *Term = ExitBB->getTerminator();
272 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
274 // The block must end in a return statement or unreachable.
276 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
277 // an unreachable, for now. The way tailcall optimization is currently
278 // implemented means it will add an epilogue followed by a jump. That is
279 // not profitable. Also, if the callee is a special function (e.g.
280 // longjmp on x86), it can end up causing miscompilation that has not
281 // been fully understood.
283 (!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
284 !isa<UnreachableInst>(Term)))
287 // If I will have a chain, make sure no other instruction that will have a
288 // chain interposes between I and the return.
289 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
290 !isSafeToSpeculativelyExecute(I))
291 for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
295 // Debug info intrinsics do not get in the way of tail call optimization.
296 if (isa<DbgInfoIntrinsic>(BBI))
298 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
299 !isSafeToSpeculativelyExecute(BBI))
303 // If the block ends with a void return or unreachable, it doesn't matter
304 // what the call's return type is.
305 if (!Ret || Ret->getNumOperands() == 0) return true;
307 // If the return value is undef, it doesn't matter what the call's
309 if (isa<UndefValue>(Ret->getOperand(0))) return true;
311 // Conservatively require the attributes of the call to match those of
312 // the return. Ignore noalias because it doesn't affect the call sequence.
313 const Function *F = ExitBB->getParent();
314 AttributeSet CallerAttrs = F->getAttributes();
315 if (AttrBuilder(CallerAttrs, AttributeSet::ReturnIndex).
316 removeAttribute(Attribute::NoAlias) !=
317 AttrBuilder(CallerAttrs, AttributeSet::ReturnIndex).
318 removeAttribute(Attribute::NoAlias))
321 // It's not safe to eliminate the sign / zero extension of the return value.
322 if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
323 CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
326 // Otherwise, make sure the unmodified return value of I is the return value.
327 // We handle two cases: multiple return values + scalars.
328 Value *RetVal = Ret->getOperand(0);
329 if (!isa<InsertValueInst>(RetVal) || !isa<StructType>(RetVal->getType()))
330 // Handle scalars first.
331 return getNoopInput(Ret->getOperand(0), TLI) == I;
333 // If this is an aggregate return, look through the insert/extract values and
334 // see if each is transparent.
335 for (unsigned i = 0, e =cast<StructType>(RetVal->getType())->getNumElements();
337 const Value *InScalar = FindInsertedValue(RetVal, i);
338 if (InScalar == 0) return false;
339 InScalar = getNoopInput(InScalar, TLI);
341 // If the scalar value being inserted is an extractvalue of the right index
342 // from the call, then everything is good.
343 const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(InScalar);
344 if (EVI == 0 || EVI->getOperand(0) != I || EVI->getNumIndices() != 1 ||
345 EVI->getIndices()[0] != i)