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/DerivedTypes.h"
16 #include "llvm/Function.h"
17 #include "llvm/Instructions.h"
18 #include "llvm/IntrinsicInst.h"
19 #include "llvm/LLVMContext.h"
20 #include "llvm/Module.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/SelectionDAG.h"
23 #include "llvm/Target/TargetData.h"
24 #include "llvm/Target/TargetLowering.h"
25 #include "llvm/Target/TargetOptions.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/MathExtras.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.getTargetData()->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.getTargetData()->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;
171 llvm_unreachable("Invalid FCmp predicate opcode!");
172 return ISD::SETFALSE;
175 ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
177 case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
178 case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
179 case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
180 case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
181 case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
182 case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
188 /// getICmpCondCode - Return the ISD condition code corresponding to
189 /// the given LLVM IR integer condition code.
191 ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
193 case ICmpInst::ICMP_EQ: return ISD::SETEQ;
194 case ICmpInst::ICMP_NE: return ISD::SETNE;
195 case ICmpInst::ICMP_SLE: return ISD::SETLE;
196 case ICmpInst::ICMP_ULE: return ISD::SETULE;
197 case ICmpInst::ICMP_SGE: return ISD::SETGE;
198 case ICmpInst::ICMP_UGE: return ISD::SETUGE;
199 case ICmpInst::ICMP_SLT: return ISD::SETLT;
200 case ICmpInst::ICMP_ULT: return ISD::SETULT;
201 case ICmpInst::ICMP_SGT: return ISD::SETGT;
202 case ICmpInst::ICMP_UGT: return ISD::SETUGT;
204 llvm_unreachable("Invalid ICmp predicate opcode!");
209 /// Test if the given instruction is in a position to be optimized
210 /// with a tail-call. This roughly means that it's in a block with
211 /// a return and there's nothing that needs to be scheduled
212 /// between it and the return.
214 /// This function only tests target-independent requirements.
215 bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
216 const TargetLowering &TLI) {
217 const Instruction *I = CS.getInstruction();
218 const BasicBlock *ExitBB = I->getParent();
219 const TerminatorInst *Term = ExitBB->getTerminator();
220 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
222 // The block must end in a return statement or unreachable.
224 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
225 // an unreachable, for now. The way tailcall optimization is currently
226 // implemented means it will add an epilogue followed by a jump. That is
227 // not profitable. Also, if the callee is a special function (e.g.
228 // longjmp on x86), it can end up causing miscompilation that has not
229 // been fully understood.
231 (!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
232 !isa<UnreachableInst>(Term))) return false;
234 // If I will have a chain, make sure no other instruction that will have a
235 // chain interposes between I and the return.
236 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
237 !I->isSafeToSpeculativelyExecute())
238 for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
242 // Debug info intrinsics do not get in the way of tail call optimization.
243 if (isa<DbgInfoIntrinsic>(BBI))
245 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
246 !BBI->isSafeToSpeculativelyExecute())
250 // If the block ends with a void return or unreachable, it doesn't matter
251 // what the call's return type is.
252 if (!Ret || Ret->getNumOperands() == 0) return true;
254 // If the return value is undef, it doesn't matter what the call's
256 if (isa<UndefValue>(Ret->getOperand(0))) return true;
258 // Conservatively require the attributes of the call to match those of
259 // the return. Ignore noalias because it doesn't affect the call sequence.
260 const Function *F = ExitBB->getParent();
261 unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
262 if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
265 // It's not safe to eliminate the sign / zero extension of the return value.
266 if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
269 // Otherwise, make sure the unmodified return value of I is the return value.
270 for (const Instruction *U = dyn_cast<Instruction>(Ret->getOperand(0)); ;
271 U = dyn_cast<Instruction>(U->getOperand(0))) {
278 // Check for a truly no-op truncate.
279 if (isa<TruncInst>(U) &&
280 TLI.isTruncateFree(U->getOperand(0)->getType(), U->getType()))
282 // Check for a truly no-op bitcast.
283 if (isa<BitCastInst>(U) &&
284 (U->getOperand(0)->getType() == U->getType() ||
285 (U->getOperand(0)->getType()->isPointerTy() &&
286 U->getType()->isPointerTy())))
288 // Otherwise it's not a true no-op.
295 bool llvm::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,
296 const TargetLowering &TLI) {
297 const Function *F = DAG.getMachineFunction().getFunction();
299 // Conservatively require the attributes of the call to match those of
300 // the return. Ignore noalias because it doesn't affect the call sequence.
301 unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
302 if (CallerRetAttr & ~Attribute::NoAlias)
305 // It's not safe to eliminate the sign / zero extension of the return value.
306 if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
309 // Check if the only use is a function return node.
310 return TLI.isUsedByReturnOnly(Node);