//===- MergeFunctions.cpp - Merge identical functions ---------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This pass looks for equivalent functions that are mergable and folds them. // // Order relation is defined on set of functions. It was made through // special function comparison procedure that returns // 0 when functions are equal, // -1 when Left function is less than right function, and // 1 for opposite case. We need total-ordering, so we need to maintain // four properties on the functions set: // a <= a (reflexivity) // if a <= b and b <= a then a = b (antisymmetry) // if a <= b and b <= c then a <= c (transitivity). // for all a and b: a <= b or b <= a (totality). // // Comparison iterates through each instruction in each basic block. // Functions are kept on binary tree. For each new function F we perform // lookup in binary tree. // In practice it works the following way: // -- We define Function* container class with custom "operator<" (FunctionPtr). // -- "FunctionPtr" instances are stored in std::set collection, so every // std::set::insert operation will give you result in log(N) time. // // When a match is found the functions are folded. If both functions are // overridable, we move the functionality into a new internal function and // leave two overridable thunks to it. // //===----------------------------------------------------------------------===// // // Future work: // // * virtual functions. // // Many functions have their address taken by the virtual function table for // the object they belong to. However, as long as it's only used for a lookup // and call, this is irrelevant, and we'd like to fold such functions. // // * be smarter about bitcasts. // // In order to fold functions, we will sometimes add either bitcast instructions // or bitcast constant expressions. Unfortunately, this can confound further // analysis since the two functions differ where one has a bitcast and the // other doesn't. We should learn to look through bitcasts. // // * Compare complex types with pointer types inside. // * Compare cross-reference cases. // * Compare complex expressions. // // All the three issues above could be described as ability to prove that // fA == fB == fC == fE == fF == fG in example below: // // void fA() { // fB(); // } // void fB() { // fA(); // } // // void fE() { // fF(); // } // void fF() { // fG(); // } // void fG() { // fE(); // } // // Simplest cross-reference case (fA <--> fB) was implemented in previous // versions of MergeFunctions, though it presented only in two function pairs // in test-suite (that counts >50k functions) // Though possibility to detect complex cross-referencing (e.g.: A->B->C->D->A) // could cover much more cases. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/IPO.h" #include "llvm/ADT/DenseSet.h" #include "llvm/ADT/FoldingSet.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/IR/CallSite.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/IRBuilder.h" #include "llvm/IR/InlineAsm.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/LLVMContext.h" #include "llvm/IR/Module.h" #include "llvm/IR/Operator.h" #include "llvm/IR/ValueHandle.h" #include "llvm/Pass.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" #include <vector> using namespace llvm; #define DEBUG_TYPE "mergefunc" STATISTIC(NumFunctionsMerged, "Number of functions merged"); STATISTIC(NumThunksWritten, "Number of thunks generated"); STATISTIC(NumAliasesWritten, "Number of aliases generated"); STATISTIC(NumDoubleWeak, "Number of new functions created"); static cl::opt<unsigned> NumFunctionsForSanityCheck( "mergefunc-sanity", cl::desc("How many functions in module could be used for " "MergeFunctions pass sanity check. " "'0' disables this check. Works only with '-debug' key."), cl::init(0), cl::Hidden); namespace { /// FunctionComparator - Compares two functions to determine whether or not /// they will generate machine code with the same behaviour. DataLayout is /// used if available. The comparator always fails conservatively (erring on the /// side of claiming that two functions are different). class FunctionComparator { public: FunctionComparator(const DataLayout *DL, const Function *F1, const Function *F2) : FnL(F1), FnR(F2), DL(DL) {} /// Test whether the two functions have equivalent behaviour. int compare(); private: /// Test whether two basic blocks have equivalent behaviour. int compare(const BasicBlock *BBL, const BasicBlock *BBR); /// Constants comparison. /// Its analog to lexicographical comparison between hypothetical numbers /// of next format: /// <bitcastability-trait><raw-bit-contents> /// /// 1. Bitcastability. /// Check whether L's type could be losslessly bitcasted to R's type. /// On this stage method, in case when lossless bitcast is not possible /// method returns -1 or 1, thus also defining which type is greater in /// context of bitcastability. /// Stage 0: If types are equal in terms of cmpTypes, then we can go straight /// to the contents comparison. /// If types differ, remember types comparison result and check /// whether we still can bitcast types. /// Stage 1: Types that satisfies isFirstClassType conditions are always /// greater then others. /// Stage 2: Vector is greater then non-vector. /// If both types are vectors, then vector with greater bitwidth is /// greater. /// If both types are vectors with the same bitwidth, then types /// are bitcastable, and we can skip other stages, and go to contents /// comparison. /// Stage 3: Pointer types are greater than non-pointers. If both types are /// pointers of the same address space - go to contents comparison. /// Different address spaces: pointer with greater address space is /// greater. /// Stage 4: Types are neither vectors, nor pointers. And they differ. /// We don't know how to bitcast them. So, we better don't do it, /// and return types comparison result (so it determines the /// relationship among constants we don't know how to bitcast). /// /// Just for clearance, let's see how the set of constants could look /// on single dimension axis: /// /// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors] /// Where: NFCT - Not a FirstClassType /// FCT - FirstClassTyp: /// /// 2. Compare raw contents. /// It ignores types on this stage and only compares bits from L and R. /// Returns 0, if L and R has equivalent contents. /// -1 or 1 if values are different. /// Pretty trivial: /// 2.1. If contents are numbers, compare numbers. /// Ints with greater bitwidth are greater. Ints with same bitwidths /// compared by their contents. /// 2.2. "And so on". Just to avoid discrepancies with comments /// perhaps it would be better to read the implementation itself. /// 3. And again about overall picture. Let's look back at how the ordered set /// of constants will look like: /// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors] /// /// Now look, what could be inside [FCT, "others"], for example: /// [FCT, "others"] = /// [ /// [double 0.1], [double 1.23], /// [i32 1], [i32 2], /// { double 1.0 }, ; StructTyID, NumElements = 1 /// { i32 1 }, ; StructTyID, NumElements = 1 /// { double 1, i32 1 }, ; StructTyID, NumElements = 2 /// { i32 1, double 1 } ; StructTyID, NumElements = 2 /// ] /// /// Let's explain the order. Float numbers will be less than integers, just /// because of cmpType terms: FloatTyID < IntegerTyID. /// Floats (with same fltSemantics) are sorted according to their value. /// Then you can see integers, and they are, like a floats, /// could be easy sorted among each others. /// The structures. Structures are grouped at the tail, again because of their /// TypeID: StructTyID > IntegerTyID > FloatTyID. /// Structures with greater number of elements are greater. Structures with /// greater elements going first are greater. /// The same logic with vectors, arrays and other possible complex types. /// /// Bitcastable constants. /// Let's assume, that some constant, belongs to some group of /// "so-called-equal" values with different types, and at the same time /// belongs to another group of constants with equal types /// and "really" equal values. /// /// Now, prove that this is impossible: /// /// If constant A with type TyA is bitcastable to B with type TyB, then: /// 1. All constants with equal types to TyA, are bitcastable to B. Since /// those should be vectors (if TyA is vector), pointers /// (if TyA is pointer), or else (if TyA equal to TyB), those types should /// be equal to TyB. /// 2. All constants with non-equal, but bitcastable types to TyA, are /// bitcastable to B. /// Once again, just because we allow it to vectors and pointers only. /// This statement could be expanded as below: /// 2.1. All vectors with equal bitwidth to vector A, has equal bitwidth to /// vector B, and thus bitcastable to B as well. /// 2.2. All pointers of the same address space, no matter what they point to, /// bitcastable. So if C is pointer, it could be bitcasted to A and to B. /// So any constant equal or bitcastable to A is equal or bitcastable to B. /// QED. /// /// In another words, for pointers and vectors, we ignore top-level type and /// look at their particular properties (bit-width for vectors, and /// address space for pointers). /// If these properties are equal - compare their contents. int cmpConstants(const Constant *L, const Constant *R); /// Assign or look up previously assigned numbers for the two values, and /// return whether the numbers are equal. Numbers are assigned in the order /// visited. /// Comparison order: /// Stage 0: Value that is function itself is always greater then others. /// If left and right values are references to their functions, then /// they are equal. /// Stage 1: Constants are greater than non-constants. /// If both left and right are constants, then the result of /// cmpConstants is used as cmpValues result. /// Stage 2: InlineAsm instances are greater than others. If both left and /// right are InlineAsm instances, InlineAsm* pointers casted to /// integers and compared as numbers. /// Stage 3: For all other cases we compare order we meet these values in /// their functions. If right value was met first during scanning, /// then left value is greater. /// In another words, we compare serial numbers, for more details /// see comments for sn_mapL and sn_mapR. int cmpValues(const Value *L, const Value *R); /// Compare two Instructions for equivalence, similar to /// Instruction::isSameOperationAs but with modifications to the type /// comparison. /// Stages are listed in "most significant stage first" order: /// On each stage below, we do comparison between some left and right /// operation parts. If parts are non-equal, we assign parts comparison /// result to the operation comparison result and exit from method. /// Otherwise we proceed to the next stage. /// Stages: /// 1. Operations opcodes. Compared as numbers. /// 2. Number of operands. /// 3. Operation types. Compared with cmpType method. /// 4. Compare operation subclass optional data as stream of bytes: /// just convert it to integers and call cmpNumbers. /// 5. Compare in operation operand types with cmpType in /// most significant operand first order. /// 6. Last stage. Check operations for some specific attributes. /// For example, for Load it would be: /// 6.1.Load: volatile (as boolean flag) /// 6.2.Load: alignment (as integer numbers) /// 6.3.Load: synch-scope (as integer numbers) /// 6.4.Load: range metadata (as integer numbers) /// On this stage its better to see the code, since its not more than 10-15 /// strings for particular instruction, and could change sometimes. int cmpOperation(const Instruction *L, const Instruction *R) const; /// Compare two GEPs for equivalent pointer arithmetic. /// Parts to be compared for each comparison stage, /// most significant stage first: /// 1. Address space. As numbers. /// 2. Constant offset, (if "DataLayout *DL" field is not NULL, /// using GEPOperator::accumulateConstantOffset method). /// 3. Pointer operand type (using cmpType method). /// 4. Number of operands. /// 5. Compare operands, using cmpValues method. int cmpGEP(const GEPOperator *GEPL, const GEPOperator *GEPR); int cmpGEP(const GetElementPtrInst *GEPL, const GetElementPtrInst *GEPR) { return cmpGEP(cast<GEPOperator>(GEPL), cast<GEPOperator>(GEPR)); } /// cmpType - compares two types, /// defines total ordering among the types set. /// /// Return values: /// 0 if types are equal, /// -1 if Left is less than Right, /// +1 if Left is greater than Right. /// /// Description: /// Comparison is broken onto stages. Like in lexicographical comparison /// stage coming first has higher priority. /// On each explanation stage keep in mind total ordering properties. /// /// 0. Before comparison we coerce pointer types of 0 address space to /// integer. /// We also don't bother with same type at left and right, so /// just return 0 in this case. /// /// 1. If types are of different kind (different type IDs). /// Return result of type IDs comparison, treating them as numbers. /// 2. If types are vectors or integers, compare Type* values as numbers. /// 3. Types has same ID, so check whether they belongs to the next group: /// * Void /// * Float /// * Double /// * X86_FP80 /// * FP128 /// * PPC_FP128 /// * Label /// * Metadata /// If so - return 0, yes - we can treat these types as equal only because /// their IDs are same. /// 4. If Left and Right are pointers, return result of address space /// comparison (numbers comparison). We can treat pointer types of same /// address space as equal. /// 5. If types are complex. /// Then both Left and Right are to be expanded and their element types will /// be checked with the same way. If we get Res != 0 on some stage, return it. /// Otherwise return 0. /// 6. For all other cases put llvm_unreachable. int cmpType(Type *TyL, Type *TyR) const; int cmpNumbers(uint64_t L, uint64_t R) const; int cmpAPInt(const APInt &L, const APInt &R) const; int cmpAPFloat(const APFloat &L, const APFloat &R) const; int cmpStrings(StringRef L, StringRef R) const; int cmpAttrs(const AttributeSet L, const AttributeSet R) const; // The two functions undergoing comparison. const Function *FnL, *FnR; const DataLayout *DL; /// Assign serial numbers to values from left function, and values from /// right function. /// Explanation: /// Being comparing functions we need to compare values we meet at left and /// right sides. /// Its easy to sort things out for external values. It just should be /// the same value at left and right. /// But for local values (those were introduced inside function body) /// we have to ensure they were introduced at exactly the same place, /// and plays the same role. /// Let's assign serial number to each value when we meet it first time. /// Values that were met at same place will be with same serial numbers. /// In this case it would be good to explain few points about values assigned /// to BBs and other ways of implementation (see below). /// /// 1. Safety of BB reordering. /// It's safe to change the order of BasicBlocks in function. /// Relationship with other functions and serial numbering will not be /// changed in this case. /// As follows from FunctionComparator::compare(), we do CFG walk: we start /// from the entry, and then take each terminator. So it doesn't matter how in /// fact BBs are ordered in function. And since cmpValues are called during /// this walk, the numbering depends only on how BBs located inside the CFG. /// So the answer is - yes. We will get the same numbering. /// /// 2. Impossibility to use dominance properties of values. /// If we compare two instruction operands: first is usage of local /// variable AL from function FL, and second is usage of local variable AR /// from FR, we could compare their origins and check whether they are /// defined at the same place. /// But, we are still not able to compare operands of PHI nodes, since those /// could be operands from further BBs we didn't scan yet. /// So it's impossible to use dominance properties in general. DenseMap<const Value*, int> sn_mapL, sn_mapR; }; class FunctionPtr { AssertingVH<Function> F; const DataLayout *DL; public: FunctionPtr(Function *F, const DataLayout *DL) : F(F), DL(DL) {} Function *getFunc() const { return F; } void release() { F = 0; } bool operator<(const FunctionPtr &RHS) const { return (FunctionComparator(DL, F, RHS.getFunc()).compare()) == -1; } }; } int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const { if (L < R) return -1; if (L > R) return 1; return 0; } int FunctionComparator::cmpAPInt(const APInt &L, const APInt &R) const { if (int Res = cmpNumbers(L.getBitWidth(), R.getBitWidth())) return Res; if (L.ugt(R)) return 1; if (R.ugt(L)) return -1; return 0; } int FunctionComparator::cmpAPFloat(const APFloat &L, const APFloat &R) const { if (int Res = cmpNumbers((uint64_t)&L.getSemantics(), (uint64_t)&R.getSemantics())) return Res; return cmpAPInt(L.bitcastToAPInt(), R.bitcastToAPInt()); } int FunctionComparator::cmpStrings(StringRef L, StringRef R) const { // Prevent heavy comparison, compare sizes first. if (int Res = cmpNumbers(L.size(), R.size())) return Res; // Compare strings lexicographically only when it is necessary: only when // strings are equal in size. return L.compare(R); } int FunctionComparator::cmpAttrs(const AttributeSet L, const AttributeSet R) const { if (int Res = cmpNumbers(L.getNumSlots(), R.getNumSlots())) return Res; for (unsigned i = 0, e = L.getNumSlots(); i != e; ++i) { AttributeSet::iterator LI = L.begin(i), LE = L.end(i), RI = R.begin(i), RE = R.end(i); for (; LI != LE && RI != RE; ++LI, ++RI) { Attribute LA = *LI; Attribute RA = *RI; if (LA < RA) return -1; if (RA < LA) return 1; } if (LI != LE) return 1; if (RI != RE) return -1; } return 0; } /// Constants comparison: /// 1. Check whether type of L constant could be losslessly bitcasted to R /// type. /// 2. Compare constant contents. /// For more details see declaration comments. int FunctionComparator::cmpConstants(const Constant *L, const Constant *R) { Type *TyL = L->getType(); Type *TyR = R->getType(); // Check whether types are bitcastable. This part is just re-factored // Type::canLosslesslyBitCastTo method, but instead of returning true/false, // we also pack into result which type is "less" for us. int TypesRes = cmpType(TyL, TyR); if (TypesRes != 0) { // Types are different, but check whether we can bitcast them. if (!TyL->isFirstClassType()) { if (TyR->isFirstClassType()) return -1; // Neither TyL nor TyR are values of first class type. Return the result // of comparing the types return TypesRes; } if (!TyR->isFirstClassType()) { if (TyL->isFirstClassType()) return 1; return TypesRes; } // Vector -> Vector conversions are always lossless if the two vector types // have the same size, otherwise not. unsigned TyLWidth = 0; unsigned TyRWidth = 0; if (const VectorType *VecTyL = dyn_cast<VectorType>(TyL)) TyLWidth = VecTyL->getBitWidth(); if (const VectorType *VecTyR = dyn_cast<VectorType>(TyR)) TyRWidth = VecTyR->getBitWidth(); if (TyLWidth != TyRWidth) return cmpNumbers(TyLWidth, TyRWidth); // Zero bit-width means neither TyL nor TyR are vectors. if (!TyLWidth) { PointerType *PTyL = dyn_cast<PointerType>(TyL); PointerType *PTyR = dyn_cast<PointerType>(TyR); if (PTyL && PTyR) { unsigned AddrSpaceL = PTyL->getAddressSpace(); unsigned AddrSpaceR = PTyR->getAddressSpace(); if (int Res = cmpNumbers(AddrSpaceL, AddrSpaceR)) return Res; } if (PTyL) return 1; if (PTyR) return -1; // TyL and TyR aren't vectors, nor pointers. We don't know how to // bitcast them. return TypesRes; } } // OK, types are bitcastable, now check constant contents. if (L->isNullValue() && R->isNullValue()) return TypesRes; if (L->isNullValue() && !R->isNullValue()) return 1; if (!L->isNullValue() && R->isNullValue()) return -1; if (int Res = cmpNumbers(L->getValueID(), R->getValueID())) return Res; switch (L->getValueID()) { case Value::UndefValueVal: return TypesRes; case Value::ConstantIntVal: { const APInt &LInt = cast<ConstantInt>(L)->getValue(); const APInt &RInt = cast<ConstantInt>(R)->getValue(); return cmpAPInt(LInt, RInt); } case Value::ConstantFPVal: { const APFloat &LAPF = cast<ConstantFP>(L)->getValueAPF(); const APFloat &RAPF = cast<ConstantFP>(R)->getValueAPF(); return cmpAPFloat(LAPF, RAPF); } case Value::ConstantArrayVal: { const ConstantArray *LA = cast<ConstantArray>(L); const ConstantArray *RA = cast<ConstantArray>(R); uint64_t NumElementsL = cast<ArrayType>(TyL)->getNumElements(); uint64_t NumElementsR = cast<ArrayType>(TyR)->getNumElements(); if (int Res = cmpNumbers(NumElementsL, NumElementsR)) return Res; for (uint64_t i = 0; i < NumElementsL; ++i) { if (int Res = cmpConstants(cast<Constant>(LA->getOperand(i)), cast<Constant>(RA->getOperand(i)))) return Res; } return 0; } case Value::ConstantStructVal: { const ConstantStruct *LS = cast<ConstantStruct>(L); const ConstantStruct *RS = cast<ConstantStruct>(R); unsigned NumElementsL = cast<StructType>(TyL)->getNumElements(); unsigned NumElementsR = cast<StructType>(TyR)->getNumElements(); if (int Res = cmpNumbers(NumElementsL, NumElementsR)) return Res; for (unsigned i = 0; i != NumElementsL; ++i) { if (int Res = cmpConstants(cast<Constant>(LS->getOperand(i)), cast<Constant>(RS->getOperand(i)))) return Res; } return 0; } case Value::ConstantVectorVal: { const ConstantVector *LV = cast<ConstantVector>(L); const ConstantVector *RV = cast<ConstantVector>(R); unsigned NumElementsL = cast<VectorType>(TyL)->getNumElements(); unsigned NumElementsR = cast<VectorType>(TyR)->getNumElements(); if (int Res = cmpNumbers(NumElementsL, NumElementsR)) return Res; for (uint64_t i = 0; i < NumElementsL; ++i) { if (int Res = cmpConstants(cast<Constant>(LV->getOperand(i)), cast<Constant>(RV->getOperand(i)))) return Res; } return 0; } case Value::ConstantExprVal: { const ConstantExpr *LE = cast<ConstantExpr>(L); const ConstantExpr *RE = cast<ConstantExpr>(R); unsigned NumOperandsL = LE->getNumOperands(); unsigned NumOperandsR = RE->getNumOperands(); if (int Res = cmpNumbers(NumOperandsL, NumOperandsR)) return Res; for (unsigned i = 0; i < NumOperandsL; ++i) { if (int Res = cmpConstants(cast<Constant>(LE->getOperand(i)), cast<Constant>(RE->getOperand(i)))) return Res; } return 0; } case Value::FunctionVal: case Value::GlobalVariableVal: case Value::GlobalAliasVal: default: // Unknown constant, cast L and R pointers to numbers and compare. return cmpNumbers((uint64_t)L, (uint64_t)R); } } /// cmpType - compares two types, /// defines total ordering among the types set. /// See method declaration comments for more details. int FunctionComparator::cmpType(Type *TyL, Type *TyR) const { PointerType *PTyL = dyn_cast<PointerType>(TyL); PointerType *PTyR = dyn_cast<PointerType>(TyR); if (DL) { if (PTyL && PTyL->getAddressSpace() == 0) TyL = DL->getIntPtrType(TyL); if (PTyR && PTyR->getAddressSpace() == 0) TyR = DL->getIntPtrType(TyR); } if (TyL == TyR) return 0; if (int Res = cmpNumbers(TyL->getTypeID(), TyR->getTypeID())) return Res; switch (TyL->getTypeID()) { default: llvm_unreachable("Unknown type!"); // Fall through in Release mode. case Type::IntegerTyID: case Type::VectorTyID: // TyL == TyR would have returned true earlier. return cmpNumbers((uint64_t)TyL, (uint64_t)TyR); case Type::VoidTyID: case Type::FloatTyID: case Type::DoubleTyID: case Type::X86_FP80TyID: case Type::FP128TyID: case Type::PPC_FP128TyID: case Type::LabelTyID: case Type::MetadataTyID: return 0; case Type::PointerTyID: { assert(PTyL && PTyR && "Both types must be pointers here."); return cmpNumbers(PTyL->getAddressSpace(), PTyR->getAddressSpace()); } case Type::StructTyID: { StructType *STyL = cast<StructType>(TyL); StructType *STyR = cast<StructType>(TyR); if (STyL->getNumElements() != STyR->getNumElements()) return cmpNumbers(STyL->getNumElements(), STyR->getNumElements()); if (STyL->isPacked() != STyR->isPacked()) return cmpNumbers(STyL->isPacked(), STyR->isPacked()); for (unsigned i = 0, e = STyL->getNumElements(); i != e; ++i) { if (int Res = cmpType(STyL->getElementType(i), STyR->getElementType(i))) return Res; } return 0; } case Type::FunctionTyID: { FunctionType *FTyL = cast<FunctionType>(TyL); FunctionType *FTyR = cast<FunctionType>(TyR); if (FTyL->getNumParams() != FTyR->getNumParams()) return cmpNumbers(FTyL->getNumParams(), FTyR->getNumParams()); if (FTyL->isVarArg() != FTyR->isVarArg()) return cmpNumbers(FTyL->isVarArg(), FTyR->isVarArg()); if (int Res = cmpType(FTyL->getReturnType(), FTyR->getReturnType())) return Res; for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) { if (int Res = cmpType(FTyL->getParamType(i), FTyR->getParamType(i))) return Res; } return 0; } case Type::ArrayTyID: { ArrayType *ATyL = cast<ArrayType>(TyL); ArrayType *ATyR = cast<ArrayType>(TyR); if (ATyL->getNumElements() != ATyR->getNumElements()) return cmpNumbers(ATyL->getNumElements(), ATyR->getNumElements()); return cmpType(ATyL->getElementType(), ATyR->getElementType()); } } } // Determine whether the two operations are the same except that pointer-to-A // and pointer-to-B are equivalent. This should be kept in sync with // Instruction::isSameOperationAs. // Read method declaration comments for more details. int FunctionComparator::cmpOperation(const Instruction *L, const Instruction *R) const { // Differences from Instruction::isSameOperationAs: // * replace type comparison with calls to isEquivalentType. // * we test for I->hasSameSubclassOptionalData (nuw/nsw/tail) at the top // * because of the above, we don't test for the tail bit on calls later on if (int Res = cmpNumbers(L->getOpcode(), R->getOpcode())) return Res; if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands())) return Res; if (int Res = cmpType(L->getType(), R->getType())) return Res; if (int Res = cmpNumbers(L->getRawSubclassOptionalData(), R->getRawSubclassOptionalData())) return Res; // We have two instructions of identical opcode and #operands. Check to see // if all operands are the same type for (unsigned i = 0, e = L->getNumOperands(); i != e; ++i) { if (int Res = cmpType(L->getOperand(i)->getType(), R->getOperand(i)->getType())) return Res; } // Check special state that is a part of some instructions. if (const LoadInst *LI = dyn_cast<LoadInst>(L)) { if (int Res = cmpNumbers(LI->isVolatile(), cast<LoadInst>(R)->isVolatile())) return Res; if (int Res = cmpNumbers(LI->getAlignment(), cast<LoadInst>(R)->getAlignment())) return Res; if (int Res = cmpNumbers(LI->getOrdering(), cast<LoadInst>(R)->getOrdering())) return Res; if (int Res = cmpNumbers(LI->getSynchScope(), cast<LoadInst>(R)->getSynchScope())) return Res; return cmpNumbers((uint64_t)LI->getMetadata(LLVMContext::MD_range), (uint64_t)cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range)); } if (const StoreInst *SI = dyn_cast<StoreInst>(L)) { if (int Res = cmpNumbers(SI->isVolatile(), cast<StoreInst>(R)->isVolatile())) return Res; if (int Res = cmpNumbers(SI->getAlignment(), cast<StoreInst>(R)->getAlignment())) return Res; if (int Res = cmpNumbers(SI->getOrdering(), cast<StoreInst>(R)->getOrdering())) return Res; return cmpNumbers(SI->getSynchScope(), cast<StoreInst>(R)->getSynchScope()); } if (const CmpInst *CI = dyn_cast<CmpInst>(L)) return cmpNumbers(CI->getPredicate(), cast<CmpInst>(R)->getPredicate()); if (const CallInst *CI = dyn_cast<CallInst>(L)) { if (int Res = cmpNumbers(CI->getCallingConv(), cast<CallInst>(R)->getCallingConv())) return Res; return cmpAttrs(CI->getAttributes(), cast<CallInst>(R)->getAttributes()); } if (const InvokeInst *CI = dyn_cast<InvokeInst>(L)) { if (int Res = cmpNumbers(CI->getCallingConv(), cast<InvokeInst>(R)->getCallingConv())) return Res; return cmpAttrs(CI->getAttributes(), cast<InvokeInst>(R)->getAttributes()); } if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(L)) { ArrayRef<unsigned> LIndices = IVI->getIndices(); ArrayRef<unsigned> RIndices = cast<InsertValueInst>(R)->getIndices(); if (int Res = cmpNumbers(LIndices.size(), RIndices.size())) return Res; for (size_t i = 0, e = LIndices.size(); i != e; ++i) { if (int Res = cmpNumbers(LIndices[i], RIndices[i])) return Res; } } if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(L)) { ArrayRef<unsigned> LIndices = EVI->getIndices(); ArrayRef<unsigned> RIndices = cast<ExtractValueInst>(R)->getIndices(); if (int Res = cmpNumbers(LIndices.size(), RIndices.size())) return Res; for (size_t i = 0, e = LIndices.size(); i != e; ++i) { if (int Res = cmpNumbers(LIndices[i], RIndices[i])) return Res; } } if (const FenceInst *FI = dyn_cast<FenceInst>(L)) { if (int Res = cmpNumbers(FI->getOrdering(), cast<FenceInst>(R)->getOrdering())) return Res; return cmpNumbers(FI->getSynchScope(), cast<FenceInst>(R)->getSynchScope()); } if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(L)) { if (int Res = cmpNumbers(CXI->isVolatile(), cast<AtomicCmpXchgInst>(R)->isVolatile())) return Res; if (int Res = cmpNumbers(CXI->isWeak(), cast<AtomicCmpXchgInst>(R)->isWeak())) return Res; if (int Res = cmpNumbers(CXI->getSuccessOrdering(), cast<AtomicCmpXchgInst>(R)->getSuccessOrdering())) return Res; if (int Res = cmpNumbers(CXI->getFailureOrdering(), cast<AtomicCmpXchgInst>(R)->getFailureOrdering())) return Res; return cmpNumbers(CXI->getSynchScope(), cast<AtomicCmpXchgInst>(R)->getSynchScope()); } if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(L)) { if (int Res = cmpNumbers(RMWI->getOperation(), cast<AtomicRMWInst>(R)->getOperation())) return Res; if (int Res = cmpNumbers(RMWI->isVolatile(), cast<AtomicRMWInst>(R)->isVolatile())) return Res; if (int Res = cmpNumbers(RMWI->getOrdering(), cast<AtomicRMWInst>(R)->getOrdering())) return Res; return cmpNumbers(RMWI->getSynchScope(), cast<AtomicRMWInst>(R)->getSynchScope()); } return 0; } // Determine whether two GEP operations perform the same underlying arithmetic. // Read method declaration comments for more details. int FunctionComparator::cmpGEP(const GEPOperator *GEPL, const GEPOperator *GEPR) { unsigned int ASL = GEPL->getPointerAddressSpace(); unsigned int ASR = GEPR->getPointerAddressSpace(); if (int Res = cmpNumbers(ASL, ASR)) return Res; // When we have target data, we can reduce the GEP down to the value in bytes // added to the address. if (DL) { unsigned BitWidth = DL->getPointerSizeInBits(ASL); APInt OffsetL(BitWidth, 0), OffsetR(BitWidth, 0); if (GEPL->accumulateConstantOffset(*DL, OffsetL) && GEPR->accumulateConstantOffset(*DL, OffsetR)) return cmpAPInt(OffsetL, OffsetR); } if (int Res = cmpNumbers((uint64_t)GEPL->getPointerOperand()->getType(), (uint64_t)GEPR->getPointerOperand()->getType())) return Res; if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands())) return Res; for (unsigned i = 0, e = GEPL->getNumOperands(); i != e; ++i) { if (int Res = cmpValues(GEPL->getOperand(i), GEPR->getOperand(i))) return Res; } return 0; } /// Compare two values used by the two functions under pair-wise comparison. If /// this is the first time the values are seen, they're added to the mapping so /// that we will detect mismatches on next use. /// See comments in declaration for more details. int FunctionComparator::cmpValues(const Value *L, const Value *R) { // Catch self-reference case. if (L == FnL) { if (R == FnR) return 0; return -1; } if (R == FnR) { if (L == FnL) return 0; return 1; } const Constant *ConstL = dyn_cast<Constant>(L); const Constant *ConstR = dyn_cast<Constant>(R); if (ConstL && ConstR) { if (L == R) return 0; return cmpConstants(ConstL, ConstR); } if (ConstL) return 1; if (ConstR) return -1; const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L); const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R); if (InlineAsmL && InlineAsmR) return cmpNumbers((uint64_t)L, (uint64_t)R); if (InlineAsmL) return 1; if (InlineAsmR) return -1; auto LeftSN = sn_mapL.insert(std::make_pair(L, sn_mapL.size())), RightSN = sn_mapR.insert(std::make_pair(R, sn_mapR.size())); return cmpNumbers(LeftSN.first->second, RightSN.first->second); } // Test whether two basic blocks have equivalent behaviour. int FunctionComparator::compare(const BasicBlock *BBL, const BasicBlock *BBR) { BasicBlock::const_iterator InstL = BBL->begin(), InstLE = BBL->end(); BasicBlock::const_iterator InstR = BBR->begin(), InstRE = BBR->end(); do { if (int Res = cmpValues(InstL, InstR)) return Res; const GetElementPtrInst *GEPL = dyn_cast<GetElementPtrInst>(InstL); const GetElementPtrInst *GEPR = dyn_cast<GetElementPtrInst>(InstR); if (GEPL && !GEPR) return 1; if (GEPR && !GEPL) return -1; if (GEPL && GEPR) { if (int Res = cmpValues(GEPL->getPointerOperand(), GEPR->getPointerOperand())) return Res; if (int Res = cmpGEP(GEPL, GEPR)) return Res; } else { if (int Res = cmpOperation(InstL, InstR)) return Res; assert(InstL->getNumOperands() == InstR->getNumOperands()); for (unsigned i = 0, e = InstL->getNumOperands(); i != e; ++i) { Value *OpL = InstL->getOperand(i); Value *OpR = InstR->getOperand(i); if (int Res = cmpValues(OpL, OpR)) return Res; if (int Res = cmpNumbers(OpL->getValueID(), OpR->getValueID())) return Res; // TODO: Already checked in cmpOperation if (int Res = cmpType(OpL->getType(), OpR->getType())) return Res; } } ++InstL, ++InstR; } while (InstL != InstLE && InstR != InstRE); if (InstL != InstLE && InstR == InstRE) return 1; if (InstL == InstLE && InstR != InstRE) return -1; return 0; } // Test whether the two functions have equivalent behaviour. int FunctionComparator::compare() { sn_mapL.clear(); sn_mapR.clear(); if (int Res = cmpAttrs(FnL->getAttributes(), FnR->getAttributes())) return Res; if (int Res = cmpNumbers(FnL->hasGC(), FnR->hasGC())) return Res; if (FnL->hasGC()) { if (int Res = cmpNumbers((uint64_t)FnL->getGC(), (uint64_t)FnR->getGC())) return Res; } if (int Res = cmpNumbers(FnL->hasSection(), FnR->hasSection())) return Res; if (FnL->hasSection()) { if (int Res = cmpStrings(FnL->getSection(), FnR->getSection())) return Res; } if (int Res = cmpNumbers(FnL->isVarArg(), FnR->isVarArg())) return Res; // TODO: if it's internal and only used in direct calls, we could handle this // case too. if (int Res = cmpNumbers(FnL->getCallingConv(), FnR->getCallingConv())) return Res; if (int Res = cmpType(FnL->getFunctionType(), FnR->getFunctionType())) return Res; assert(FnL->arg_size() == FnR->arg_size() && "Identically typed functions have different numbers of args!"); // Visit the arguments so that they get enumerated in the order they're // passed in. for (Function::const_arg_iterator ArgLI = FnL->arg_begin(), ArgRI = FnR->arg_begin(), ArgLE = FnL->arg_end(); ArgLI != ArgLE; ++ArgLI, ++ArgRI) { if (cmpValues(ArgLI, ArgRI) != 0) llvm_unreachable("Arguments repeat!"); } // We do a CFG-ordered walk since the actual ordering of the blocks in the // linked list is immaterial. Our walk starts at the entry block for both // functions, then takes each block from each terminator in order. As an // artifact, this also means that unreachable blocks are ignored. SmallVector<const BasicBlock *, 8> FnLBBs, FnRBBs; SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1. FnLBBs.push_back(&FnL->getEntryBlock()); FnRBBs.push_back(&FnR->getEntryBlock()); VisitedBBs.insert(FnLBBs[0]); while (!FnLBBs.empty()) { const BasicBlock *BBL = FnLBBs.pop_back_val(); const BasicBlock *BBR = FnRBBs.pop_back_val(); if (int Res = cmpValues(BBL, BBR)) return Res; if (int Res = compare(BBL, BBR)) return Res; const TerminatorInst *TermL = BBL->getTerminator(); const TerminatorInst *TermR = BBR->getTerminator(); assert(TermL->getNumSuccessors() == TermR->getNumSuccessors()); for (unsigned i = 0, e = TermL->getNumSuccessors(); i != e; ++i) { if (!VisitedBBs.insert(TermL->getSuccessor(i))) continue; FnLBBs.push_back(TermL->getSuccessor(i)); FnRBBs.push_back(TermR->getSuccessor(i)); } } return 0; } namespace { /// MergeFunctions finds functions which will generate identical machine code, /// by considering all pointer types to be equivalent. Once identified, /// MergeFunctions will fold them by replacing a call to one to a call to a /// bitcast of the other. /// class MergeFunctions : public ModulePass { public: static char ID; MergeFunctions() : ModulePass(ID), HasGlobalAliases(false) { initializeMergeFunctionsPass(*PassRegistry::getPassRegistry()); } bool runOnModule(Module &M) override; private: typedef std::set<FunctionPtr> FnTreeType; /// A work queue of functions that may have been modified and should be /// analyzed again. std::vector<WeakVH> Deferred; /// Checks the rules of order relation introduced among functions set. /// Returns true, if sanity check has been passed, and false if failed. bool doSanityCheck(std::vector<WeakVH> &Worklist); /// Insert a ComparableFunction into the FnTree, or merge it away if it's /// equal to one that's already present. bool insert(Function *NewFunction); /// Remove a Function from the FnTree and queue it up for a second sweep of /// analysis. void remove(Function *F); /// Find the functions that use this Value and remove them from FnTree and /// queue the functions. void removeUsers(Value *V); /// Replace all direct calls of Old with calls of New. Will bitcast New if /// necessary to make types match. void replaceDirectCallers(Function *Old, Function *New); /// Merge two equivalent functions. Upon completion, G may be deleted, or may /// be converted into a thunk. In either case, it should never be visited /// again. void mergeTwoFunctions(Function *F, Function *G); /// Replace G with a thunk or an alias to F. Deletes G. void writeThunkOrAlias(Function *F, Function *G); /// Replace G with a simple tail call to bitcast(F). Also replace direct uses /// of G with bitcast(F). Deletes G. void writeThunk(Function *F, Function *G); /// Replace G with an alias to F. Deletes G. void writeAlias(Function *F, Function *G); /// The set of all distinct functions. Use the insert() and remove() methods /// to modify it. FnTreeType FnTree; /// DataLayout for more accurate GEP comparisons. May be NULL. const DataLayout *DL; /// Whether or not the target supports global aliases. bool HasGlobalAliases; }; } // end anonymous namespace char MergeFunctions::ID = 0; INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false) ModulePass *llvm::createMergeFunctionsPass() { return new MergeFunctions(); } bool MergeFunctions::doSanityCheck(std::vector<WeakVH> &Worklist) { if (const unsigned Max = NumFunctionsForSanityCheck) { unsigned TripleNumber = 0; bool Valid = true; dbgs() << "MERGEFUNC-SANITY: Started for first " << Max << " functions.\n"; unsigned i = 0; for (std::vector<WeakVH>::iterator I = Worklist.begin(), E = Worklist.end(); I != E && i < Max; ++I, ++i) { unsigned j = i; for (std::vector<WeakVH>::iterator J = I; J != E && j < Max; ++J, ++j) { Function *F1 = cast<Function>(*I); Function *F2 = cast<Function>(*J); int Res1 = FunctionComparator(DL, F1, F2).compare(); int Res2 = FunctionComparator(DL, F2, F1).compare(); // If F1 <= F2, then F2 >= F1, otherwise report failure. if (Res1 != -Res2) { dbgs() << "MERGEFUNC-SANITY: Non-symmetric; triple: " << TripleNumber << "\n"; F1->dump(); F2->dump(); Valid = false; } if (Res1 == 0) continue; unsigned k = j; for (std::vector<WeakVH>::iterator K = J; K != E && k < Max; ++k, ++K, ++TripleNumber) { if (K == J) continue; Function *F3 = cast<Function>(*K); int Res3 = FunctionComparator(DL, F1, F3).compare(); int Res4 = FunctionComparator(DL, F2, F3).compare(); bool Transitive = true; if (Res1 != 0 && Res1 == Res4) { // F1 > F2, F2 > F3 => F1 > F3 Transitive = Res3 == Res1; } else if (Res3 != 0 && Res3 == -Res4) { // F1 > F3, F3 > F2 => F1 > F2 Transitive = Res3 == Res1; } else if (Res4 != 0 && -Res3 == Res4) { // F2 > F3, F3 > F1 => F2 > F1 Transitive = Res4 == -Res1; } if (!Transitive) { dbgs() << "MERGEFUNC-SANITY: Non-transitive; triple: " << TripleNumber << "\n"; dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", " << Res4 << "\n"; F1->dump(); F2->dump(); F3->dump(); Valid = false; } } } } dbgs() << "MERGEFUNC-SANITY: " << (Valid ? "Passed." : "Failed.") << "\n"; return Valid; } return true; } bool MergeFunctions::runOnModule(Module &M) { bool Changed = false; DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); DL = DLP ? &DLP->getDataLayout() : nullptr; for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) { if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage()) Deferred.push_back(WeakVH(I)); } do { std::vector<WeakVH> Worklist; Deferred.swap(Worklist); DEBUG(doSanityCheck(Worklist)); DEBUG(dbgs() << "size of module: " << M.size() << '\n'); DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n'); // Insert only strong functions and merge them. Strong function merging // always deletes one of them. for (std::vector<WeakVH>::iterator I = Worklist.begin(), E = Worklist.end(); I != E; ++I) { if (!*I) continue; Function *F = cast<Function>(*I); if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() && !F->mayBeOverridden()) { Changed |= insert(F); } } // Insert only weak functions and merge them. By doing these second we // create thunks to the strong function when possible. When two weak // functions are identical, we create a new strong function with two weak // weak thunks to it which are identical but not mergable. for (std::vector<WeakVH>::iterator I = Worklist.begin(), E = Worklist.end(); I != E; ++I) { if (!*I) continue; Function *F = cast<Function>(*I); if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() && F->mayBeOverridden()) { Changed |= insert(F); } } DEBUG(dbgs() << "size of FnTree: " << FnTree.size() << '\n'); } while (!Deferred.empty()); FnTree.clear(); return Changed; } // Replace direct callers of Old with New. void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) { Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType()); for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) { Use *U = &*UI; ++UI; CallSite CS(U->getUser()); if (CS && CS.isCallee(U)) { remove(CS.getInstruction()->getParent()->getParent()); U->set(BitcastNew); } } } // Replace G with an alias to F if possible, or else a thunk to F. Deletes G. void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) { if (HasGlobalAliases && G->hasUnnamedAddr()) { if (G->hasExternalLinkage() || G->hasLocalLinkage() || G->hasWeakLinkage()) { writeAlias(F, G); return; } } writeThunk(F, G); } // Helper for writeThunk, // Selects proper bitcast operation, // but a bit simpler then CastInst::getCastOpcode. static Value *createCast(IRBuilder<false> &Builder, Value *V, Type *DestTy) { Type *SrcTy = V->getType(); if (SrcTy->isStructTy()) { assert(DestTy->isStructTy()); assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements()); Value *Result = UndefValue::get(DestTy); for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) { Value *Element = createCast( Builder, Builder.CreateExtractValue(V, ArrayRef<unsigned int>(I)), DestTy->getStructElementType(I)); Result = Builder.CreateInsertValue(Result, Element, ArrayRef<unsigned int>(I)); } return Result; } assert(!DestTy->isStructTy()); if (SrcTy->isIntegerTy() && DestTy->isPointerTy()) return Builder.CreateIntToPtr(V, DestTy); else if (SrcTy->isPointerTy() && DestTy->isIntegerTy()) return Builder.CreatePtrToInt(V, DestTy); else return Builder.CreateBitCast(V, DestTy); } // Replace G with a simple tail call to bitcast(F). Also replace direct uses // of G with bitcast(F). Deletes G. void MergeFunctions::writeThunk(Function *F, Function *G) { if (!G->mayBeOverridden()) { // Redirect direct callers of G to F. replaceDirectCallers(G, F); } // If G was internal then we may have replaced all uses of G with F. If so, // stop here and delete G. There's no need for a thunk. if (G->hasLocalLinkage() && G->use_empty()) { G->eraseFromParent(); return; } Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "", G->getParent()); BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG); IRBuilder<false> Builder(BB); SmallVector<Value *, 16> Args; unsigned i = 0; FunctionType *FFTy = F->getFunctionType(); for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end(); AI != AE; ++AI) { Args.push_back(createCast(Builder, (Value*)AI, FFTy->getParamType(i))); ++i; } CallInst *CI = Builder.CreateCall(F, Args); CI->setTailCall(); CI->setCallingConv(F->getCallingConv()); if (NewG->getReturnType()->isVoidTy()) { Builder.CreateRetVoid(); } else { Builder.CreateRet(createCast(Builder, CI, NewG->getReturnType())); } NewG->copyAttributesFrom(G); NewG->takeName(G); removeUsers(G); G->replaceAllUsesWith(NewG); G->eraseFromParent(); DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n'); ++NumThunksWritten; } // Replace G with an alias to F and delete G. void MergeFunctions::writeAlias(Function *F, Function *G) { PointerType *PTy = G->getType(); auto *GA = GlobalAlias::create(PTy->getElementType(), PTy->getAddressSpace(), G->getLinkage(), "", F); F->setAlignment(std::max(F->getAlignment(), G->getAlignment())); GA->takeName(G); GA->setVisibility(G->getVisibility()); removeUsers(G); G->replaceAllUsesWith(GA); G->eraseFromParent(); DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n'); ++NumAliasesWritten; } // Merge two equivalent functions. Upon completion, Function G is deleted. void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) { if (F->mayBeOverridden()) { assert(G->mayBeOverridden()); if (HasGlobalAliases) { // Make them both thunks to the same internal function. Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "", F->getParent()); H->copyAttributesFrom(F); H->takeName(F); removeUsers(F); F->replaceAllUsesWith(H); unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment()); writeAlias(F, G); writeAlias(F, H); F->setAlignment(MaxAlignment); F->setLinkage(GlobalValue::PrivateLinkage); } else { // We can't merge them. Instead, pick one and update all direct callers // to call it and hope that we improve the instruction cache hit rate. replaceDirectCallers(G, F); } ++NumDoubleWeak; } else { writeThunkOrAlias(F, G); } ++NumFunctionsMerged; } // Insert a ComparableFunction into the FnTree, or merge it away if equal to one // that was already inserted. bool MergeFunctions::insert(Function *NewFunction) { std::pair<FnTreeType::iterator, bool> Result = FnTree.insert(FunctionPtr(NewFunction, DL)); if (Result.second) { DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName() << '\n'); return false; } const FunctionPtr &OldF = *Result.first; // Don't merge tiny functions, since it can just end up making the function // larger. // FIXME: Should still merge them if they are unnamed_addr and produce an // alias. if (NewFunction->size() == 1) { if (NewFunction->front().size() <= 2) { DEBUG(dbgs() << NewFunction->getName() << " is to small to bother merging\n"); return false; } } // Never thunk a strong function to a weak function. assert(!OldF.getFunc()->mayBeOverridden() || NewFunction->mayBeOverridden()); DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == " << NewFunction->getName() << '\n'); Function *DeleteF = NewFunction; mergeTwoFunctions(OldF.getFunc(), DeleteF); return true; } // Remove a function from FnTree. If it was already in FnTree, add // it to Deferred so that we'll look at it in the next round. void MergeFunctions::remove(Function *F) { // We need to make sure we remove F, not a function "equal" to F per the // function equality comparator. FnTreeType::iterator found = FnTree.find(FunctionPtr(F, DL)); size_t Erased = 0; if (found != FnTree.end() && found->getFunc() == F) { Erased = 1; FnTree.erase(found); } if (Erased) { DEBUG(dbgs() << "Removed " << F->getName() << " from set and deferred it.\n"); Deferred.push_back(F); } } // For each instruction used by the value, remove() the function that contains // the instruction. This should happen right before a call to RAUW. void MergeFunctions::removeUsers(Value *V) { std::vector<Value *> Worklist; Worklist.push_back(V); while (!Worklist.empty()) { Value *V = Worklist.back(); Worklist.pop_back(); for (User *U : V->users()) { if (Instruction *I = dyn_cast<Instruction>(U)) { remove(I->getParent()->getParent()); } else if (isa<GlobalValue>(U)) { // do nothing } else if (Constant *C = dyn_cast<Constant>(U)) { for (User *UU : C->users()) Worklist.push_back(UU); } } } }