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llvm-mirror/lib/Transforms/IPO/MergeFunctions.cpp
Erik Eckstein 53b2b8eb9b Fix a crash in MergeFunctions related to ordering of weak/strong functions 
The assumption, made in insert() that weak functions are always inserted after strong functions,
is only true in the first round of adding functions.
In subsequent rounds this is no longer guaranteed , because we might remove a strong function from the tree (because it's modified) and add it later,
where an equivalent weak function already exists in the tree.
This change removes the assert in insert() and explicitly enforces a weak->strong order.
This also removes the need of two separate loops in runOnModule().

llvm-svn: 271299
2016-05-31 17:20:23 +00:00

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//===- 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.
//
// As an optimization, a hash of the function structure is calculated first, and
// two functions are only compared if they have the same hash. This hash is
// cheap to compute, and has the property that if function F == G according to
// the comparison function, then hash(F) == hash(G). This consistency property
// is critical to ensuring all possible merging opportunities are exploited.
// Collisions in the hash affect the speed of the pass but not the correctness
// or determinism of the resulting transformation.
//
// 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/ADT/Hashing.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/IR/ValueMap.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 "llvm/Transforms/IPO.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 {
/// GlobalNumberState assigns an integer to each global value in the program,
/// which is used by the comparison routine to order references to globals. This
/// state must be preserved throughout the pass, because Functions and other
/// globals need to maintain their relative order. Globals are assigned a number
/// when they are first visited. This order is deterministic, and so the
/// assigned numbers are as well. When two functions are merged, neither number
/// is updated. If the symbols are weak, this would be incorrect. If they are
/// strong, then one will be replaced at all references to the other, and so
/// direct callsites will now see one or the other symbol, and no update is
/// necessary. Note that if we were guaranteed unique names, we could just
/// compare those, but this would not work for stripped bitcodes or for those
/// few symbols without a name.
class GlobalNumberState {
struct Config : ValueMapConfig<GlobalValue*> {
enum { FollowRAUW = false };
};
// Each GlobalValue is mapped to an identifier. The Config ensures when RAUW
// occurs, the mapping does not change. Tracking changes is unnecessary, and
// also problematic for weak symbols (which may be overwritten).
typedef ValueMap<GlobalValue *, uint64_t, Config> ValueNumberMap;
ValueNumberMap GlobalNumbers;
// The next unused serial number to assign to a global.
uint64_t NextNumber;
public:
GlobalNumberState() : GlobalNumbers(), NextNumber(0) {}
uint64_t getNumber(GlobalValue* Global) {
ValueNumberMap::iterator MapIter;
bool Inserted;
std::tie(MapIter, Inserted) = GlobalNumbers.insert({Global, NextNumber});
if (Inserted)
NextNumber++;
return MapIter->second;
}
void clear() {
GlobalNumbers.clear();
}
};
/// 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 Function *F1, const Function *F2,
GlobalNumberState* GN)
: FnL(F1), FnR(F2), GlobalNumbers(GN) {}
/// Test whether the two functions have equivalent behaviour.
int compare();
/// Hash a function. Equivalent functions will have the same hash, and unequal
/// functions will have different hashes with high probability.
typedef uint64_t FunctionHash;
static FunctionHash functionHash(Function &);
private:
/// Test whether two basic blocks have equivalent behaviour.
int cmpBasicBlocks(const BasicBlock *BBL, const BasicBlock *BBR) const;
/// 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) const;
/// Compares two global values by number. Uses the GlobalNumbersState to
/// identify the same gobals across function calls.
int cmpGlobalValues(GlobalValue *L, GlobalValue *R) const;
/// 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) const;
/// Compare two Instructions for equivalence, similar to
/// Instruction::isSameOperationAs.
///
/// 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: ordering (as underlying enum class value)
/// 6.4.Load: synch-scope (as integer numbers)
/// 6.5.Load: range metadata (as integer ranges)
/// 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 cmpOperations(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, (using GEPOperator::accumulateConstantOffset method).
/// 3. Pointer operand type (using cmpType method).
/// 4. Number of operands.
/// 5. Compare operands, using cmpValues method.
int cmpGEPs(const GEPOperator *GEPL, const GEPOperator *GEPR) const;
int cmpGEPs(const GetElementPtrInst *GEPL,
const GetElementPtrInst *GEPR) const {
return cmpGEPs(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 integers, check that they have the same width. If they
/// are vectors, check that they have the same count and subtype.
/// 3. Types have the same ID, so check whether they are one of:
/// * Void
/// * Float
/// * Double
/// * X86_FP80
/// * FP128
/// * PPC_FP128
/// * Label
/// * Metadata
/// We can treat these types as equal whenever 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 cmpTypes(Type *TyL, Type *TyR) const;
int cmpNumbers(uint64_t L, uint64_t R) const;
int cmpOrderings(AtomicOrdering L, AtomicOrdering R) const;
int cmpAPInts(const APInt &L, const APInt &R) const;
int cmpAPFloats(const APFloat &L, const APFloat &R) const;
int cmpInlineAsm(const InlineAsm *L, const InlineAsm *R) const;
int cmpMem(StringRef L, StringRef R) const;
int cmpAttrs(const AttributeSet L, const AttributeSet R) const;
int cmpRangeMetadata(const MDNode *L, const MDNode *R) const;
int cmpOperandBundlesSchema(const Instruction *L, const Instruction *R) const;
// The two functions undergoing comparison.
const Function *FnL, *FnR;
/// 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.
mutable DenseMap<const Value*, int> sn_mapL, sn_mapR;
// The global state we will use
GlobalNumberState* GlobalNumbers;
};
class FunctionNode {
mutable AssertingVH<Function> F;
FunctionComparator::FunctionHash Hash;
public:
// Note the hash is recalculated potentially multiple times, but it is cheap.
FunctionNode(Function *F)
: F(F), Hash(FunctionComparator::functionHash(*F)) {}
Function *getFunc() const { return F; }
FunctionComparator::FunctionHash getHash() const { return Hash; }
/// Replace the reference to the function F by the function G, assuming their
/// implementations are equal.
void replaceBy(Function *G) const {
F = G;
}
void release() { F = nullptr; }
};
} // end anonymous namespace
int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
if (L < R) return -1;
if (L > R) return 1;
return 0;
}
int FunctionComparator::cmpOrderings(AtomicOrdering L, AtomicOrdering R) const {
if ((int)L < (int)R) return -1;
if ((int)L > (int)R) return 1;
return 0;
}
int FunctionComparator::cmpAPInts(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::cmpAPFloats(const APFloat &L, const APFloat &R) const {
// Floats are ordered first by semantics (i.e. float, double, half, etc.),
// then by value interpreted as a bitstring (aka APInt).
const fltSemantics &SL = L.getSemantics(), &SR = R.getSemantics();
if (int Res = cmpNumbers(APFloat::semanticsPrecision(SL),
APFloat::semanticsPrecision(SR)))
return Res;
if (int Res = cmpNumbers(APFloat::semanticsMaxExponent(SL),
APFloat::semanticsMaxExponent(SR)))
return Res;
if (int Res = cmpNumbers(APFloat::semanticsMinExponent(SL),
APFloat::semanticsMinExponent(SR)))
return Res;
if (int Res = cmpNumbers(APFloat::semanticsSizeInBits(SL),
APFloat::semanticsSizeInBits(SR)))
return Res;
return cmpAPInts(L.bitcastToAPInt(), R.bitcastToAPInt());
}
int FunctionComparator::cmpMem(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;
}
int FunctionComparator::cmpRangeMetadata(const MDNode *L,
const MDNode *R) const {
if (L == R)
return 0;
if (!L)
return -1;
if (!R)
return 1;
// Range metadata is a sequence of numbers. Make sure they are the same
// sequence.
// TODO: Note that as this is metadata, it is possible to drop and/or merge
// this data when considering functions to merge. Thus this comparison would
// return 0 (i.e. equivalent), but merging would become more complicated
// because the ranges would need to be unioned. It is not likely that
// functions differ ONLY in this metadata if they are actually the same
// function semantically.
if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
return Res;
for (size_t I = 0; I < L->getNumOperands(); ++I) {
ConstantInt *LLow = mdconst::extract<ConstantInt>(L->getOperand(I));
ConstantInt *RLow = mdconst::extract<ConstantInt>(R->getOperand(I));
if (int Res = cmpAPInts(LLow->getValue(), RLow->getValue()))
return Res;
}
return 0;
}
int FunctionComparator::cmpOperandBundlesSchema(const Instruction *L,
const Instruction *R) const {
ImmutableCallSite LCS(L);
ImmutableCallSite RCS(R);
assert(LCS && RCS && "Must be calls or invokes!");
assert(LCS.isCall() == RCS.isCall() && "Can't compare otherwise!");
if (int Res =
cmpNumbers(LCS.getNumOperandBundles(), RCS.getNumOperandBundles()))
return Res;
for (unsigned i = 0, e = LCS.getNumOperandBundles(); i != e; ++i) {
auto OBL = LCS.getOperandBundleAt(i);
auto OBR = RCS.getOperandBundleAt(i);
if (int Res = OBL.getTagName().compare(OBR.getTagName()))
return Res;
if (int Res = cmpNumbers(OBL.Inputs.size(), OBR.Inputs.size()))
return Res;
}
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) const {
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 = cmpTypes(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 (auto *VecTyL = dyn_cast<VectorType>(TyL))
TyLWidth = VecTyL->getBitWidth();
if (auto *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;
auto GlobalValueL = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(L));
auto GlobalValueR = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(R));
if (GlobalValueL && GlobalValueR) {
return cmpGlobalValues(GlobalValueL, GlobalValueR);
}
if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
return Res;
if (const auto *SeqL = dyn_cast<ConstantDataSequential>(L)) {
const auto *SeqR = cast<ConstantDataSequential>(R);
// This handles ConstantDataArray and ConstantDataVector. Note that we
// compare the two raw data arrays, which might differ depending on the host
// endianness. This isn't a problem though, because the endiness of a module
// will affect the order of the constants, but this order is the same
// for a given input module and host platform.
return cmpMem(SeqL->getRawDataValues(), SeqR->getRawDataValues());
}
switch (L->getValueID()) {
case Value::UndefValueVal:
case Value::ConstantTokenNoneVal:
return TypesRes;
case Value::ConstantIntVal: {
const APInt &LInt = cast<ConstantInt>(L)->getValue();
const APInt &RInt = cast<ConstantInt>(R)->getValue();
return cmpAPInts(LInt, RInt);
}
case Value::ConstantFPVal: {
const APFloat &LAPF = cast<ConstantFP>(L)->getValueAPF();
const APFloat &RAPF = cast<ConstantFP>(R)->getValueAPF();
return cmpAPFloats(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::BlockAddressVal: {
const BlockAddress *LBA = cast<BlockAddress>(L);
const BlockAddress *RBA = cast<BlockAddress>(R);
if (int Res = cmpValues(LBA->getFunction(), RBA->getFunction()))
return Res;
if (LBA->getFunction() == RBA->getFunction()) {
// They are BBs in the same function. Order by which comes first in the
// BB order of the function. This order is deterministic.
Function* F = LBA->getFunction();
BasicBlock *LBB = LBA->getBasicBlock();
BasicBlock *RBB = RBA->getBasicBlock();
if (LBB == RBB)
return 0;
for(BasicBlock &BB : F->getBasicBlockList()) {
if (&BB == LBB) {
assert(&BB != RBB);
return -1;
}
if (&BB == RBB)
return 1;
}
llvm_unreachable("Basic Block Address does not point to a basic block in "
"its function.");
return -1;
} else {
// cmpValues said the functions are the same. So because they aren't
// literally the same pointer, they must respectively be the left and
// right functions.
assert(LBA->getFunction() == FnL && RBA->getFunction() == FnR);
// cmpValues will tell us if these are equivalent BasicBlocks, in the
// context of their respective functions.
return cmpValues(LBA->getBasicBlock(), RBA->getBasicBlock());
}
}
default: // Unknown constant, abort.
DEBUG(dbgs() << "Looking at valueID " << L->getValueID() << "\n");
llvm_unreachable("Constant ValueID not recognized.");
return -1;
}
}
int FunctionComparator::cmpGlobalValues(GlobalValue *L, GlobalValue *R) const {
return cmpNumbers(GlobalNumbers->getNumber(L), GlobalNumbers->getNumber(R));
}
/// cmpType - compares two types,
/// defines total ordering among the types set.
/// See method declaration comments for more details.
int FunctionComparator::cmpTypes(Type *TyL, Type *TyR) const {
PointerType *PTyL = dyn_cast<PointerType>(TyL);
PointerType *PTyR = dyn_cast<PointerType>(TyR);
const DataLayout &DL = FnL->getParent()->getDataLayout();
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:
return cmpNumbers(cast<IntegerType>(TyL)->getBitWidth(),
cast<IntegerType>(TyR)->getBitWidth());
case Type::VectorTyID: {
VectorType *VTyL = cast<VectorType>(TyL), *VTyR = cast<VectorType>(TyR);
if (int Res = cmpNumbers(VTyL->getNumElements(), VTyR->getNumElements()))
return Res;
return cmpTypes(VTyL->getElementType(), VTyR->getElementType());
}
// TyL == TyR would have returned true earlier, because types are uniqued.
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:
case Type::TokenTyID:
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 = cmpTypes(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 = cmpTypes(FTyL->getReturnType(), FTyR->getReturnType()))
return Res;
for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) {
if (int Res = cmpTypes(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 cmpTypes(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::cmpOperations(const Instruction *L,
const Instruction *R) const {
// Differences from Instruction::isSameOperationAs:
// * replace type comparison with calls to cmpTypes.
// * we test for I->getRawSubclassOptionalData (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 = cmpTypes(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 =
cmpTypes(L->getOperand(i)->getType(), R->getOperand(i)->getType()))
return Res;
}
// Check special state that is a part of some instructions.
if (const AllocaInst *AI = dyn_cast<AllocaInst>(L)) {
if (int Res = cmpTypes(AI->getAllocatedType(),
cast<AllocaInst>(R)->getAllocatedType()))
return Res;
return cmpNumbers(AI->getAlignment(), cast<AllocaInst>(R)->getAlignment());
}
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 =
cmpOrderings(LI->getOrdering(), cast<LoadInst>(R)->getOrdering()))
return Res;
if (int Res =
cmpNumbers(LI->getSynchScope(), cast<LoadInst>(R)->getSynchScope()))
return Res;
return cmpRangeMetadata(LI->getMetadata(LLVMContext::MD_range),
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 =
cmpOrderings(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;
if (int Res =
cmpAttrs(CI->getAttributes(), cast<CallInst>(R)->getAttributes()))
return Res;
if (int Res = cmpOperandBundlesSchema(CI, R))
return Res;
return cmpRangeMetadata(
CI->getMetadata(LLVMContext::MD_range),
cast<CallInst>(R)->getMetadata(LLVMContext::MD_range));
}
if (const InvokeInst *II = dyn_cast<InvokeInst>(L)) {
if (int Res = cmpNumbers(II->getCallingConv(),
cast<InvokeInst>(R)->getCallingConv()))
return Res;
if (int Res =
cmpAttrs(II->getAttributes(), cast<InvokeInst>(R)->getAttributes()))
return Res;
if (int Res = cmpOperandBundlesSchema(II, R))
return Res;
return cmpRangeMetadata(
II->getMetadata(LLVMContext::MD_range),
cast<InvokeInst>(R)->getMetadata(LLVMContext::MD_range));
}
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;
}
return 0;
}
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 =
cmpOrderings(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 =
cmpOrderings(CXI->getSuccessOrdering(),
cast<AtomicCmpXchgInst>(R)->getSuccessOrdering()))
return Res;
if (int Res =
cmpOrderings(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 = cmpOrderings(RMWI->getOrdering(),
cast<AtomicRMWInst>(R)->getOrdering()))
return Res;
return cmpNumbers(RMWI->getSynchScope(),
cast<AtomicRMWInst>(R)->getSynchScope());
}
if (const PHINode *PNL = dyn_cast<PHINode>(L)) {
const PHINode *PNR = cast<PHINode>(R);
// Ensure that in addition to the incoming values being identical
// (checked by the caller of this function), the incoming blocks
// are also identical.
for (unsigned i = 0, e = PNL->getNumIncomingValues(); i != e; ++i) {
if (int Res =
cmpValues(PNL->getIncomingBlock(i), PNR->getIncomingBlock(i)))
return Res;
}
}
return 0;
}
// Determine whether two GEP operations perform the same underlying arithmetic.
// Read method declaration comments for more details.
int FunctionComparator::cmpGEPs(const GEPOperator *GEPL,
const GEPOperator *GEPR) const {
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.
const DataLayout &DL = FnL->getParent()->getDataLayout();
unsigned BitWidth = DL.getPointerSizeInBits(ASL);
APInt OffsetL(BitWidth, 0), OffsetR(BitWidth, 0);
if (GEPL->accumulateConstantOffset(DL, OffsetL) &&
GEPR->accumulateConstantOffset(DL, OffsetR))
return cmpAPInts(OffsetL, OffsetR);
if (int Res = cmpTypes(GEPL->getSourceElementType(),
GEPR->getSourceElementType()))
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;
}
int FunctionComparator::cmpInlineAsm(const InlineAsm *L,
const InlineAsm *R) const {
// InlineAsm's are uniqued. If they are the same pointer, obviously they are
// the same, otherwise compare the fields.
if (L == R)
return 0;
if (int Res = cmpTypes(L->getFunctionType(), R->getFunctionType()))
return Res;
if (int Res = cmpMem(L->getAsmString(), R->getAsmString()))
return Res;
if (int Res = cmpMem(L->getConstraintString(), R->getConstraintString()))
return Res;
if (int Res = cmpNumbers(L->hasSideEffects(), R->hasSideEffects()))
return Res;
if (int Res = cmpNumbers(L->isAlignStack(), R->isAlignStack()))
return Res;
if (int Res = cmpNumbers(L->getDialect(), R->getDialect()))
return Res;
llvm_unreachable("InlineAsm blocks were not uniqued.");
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) const {
// 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 cmpInlineAsm(InlineAsmL, InlineAsmR);
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::cmpBasicBlocks(const BasicBlock *BBL,
const BasicBlock *BBR) const {
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 = cmpGEPs(GEPL, GEPR))
return Res;
} else {
if (int Res = cmpOperations(&*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;
// cmpValues should ensure this is true.
assert(cmpTypes(OpL->getType(), OpR->getType()) == 0);
}
}
++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 = cmpMem(FnL->getGC(), FnR->getGC()))
return Res;
}
if (int Res = cmpNumbers(FnL->hasSection(), FnR->hasSection()))
return Res;
if (FnL->hasSection()) {
if (int Res = cmpMem(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 = cmpTypes(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;
SmallPtrSet<const BasicBlock *, 32> 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 = cmpBasicBlocks(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)).second)
continue;
FnLBBs.push_back(TermL->getSuccessor(i));
FnRBBs.push_back(TermR->getSuccessor(i));
}
}
return 0;
}
namespace {
// Accumulate the hash of a sequence of 64-bit integers. This is similar to a
// hash of a sequence of 64bit ints, but the entire input does not need to be
// available at once. This interface is necessary for functionHash because it
// needs to accumulate the hash as the structure of the function is traversed
// without saving these values to an intermediate buffer. This form of hashing
// is not often needed, as usually the object to hash is just read from a
// buffer.
class HashAccumulator64 {
uint64_t Hash;
public:
// Initialize to random constant, so the state isn't zero.
HashAccumulator64() { Hash = 0x6acaa36bef8325c5ULL; }
void add(uint64_t V) {
Hash = llvm::hashing::detail::hash_16_bytes(Hash, V);
}
// No finishing is required, because the entire hash value is used.
uint64_t getHash() { return Hash; }
};
} // end anonymous namespace
// A function hash is calculated by considering only the number of arguments and
// whether a function is varargs, the order of basic blocks (given by the
// successors of each basic block in depth first order), and the order of
// opcodes of each instruction within each of these basic blocks. This mirrors
// the strategy compare() uses to compare functions by walking the BBs in depth
// first order and comparing each instruction in sequence. Because this hash
// does not look at the operands, it is insensitive to things such as the
// target of calls and the constants used in the function, which makes it useful
// when possibly merging functions which are the same modulo constants and call
// targets.
FunctionComparator::FunctionHash FunctionComparator::functionHash(Function &F) {
HashAccumulator64 H;
H.add(F.isVarArg());
H.add(F.arg_size());
SmallVector<const BasicBlock *, 8> BBs;
SmallSet<const BasicBlock *, 16> VisitedBBs;
// Walk the blocks in the same order as FunctionComparator::cmpBasicBlocks(),
// accumulating the hash of the function "structure." (BB and opcode sequence)
BBs.push_back(&F.getEntryBlock());
VisitedBBs.insert(BBs[0]);
while (!BBs.empty()) {
const BasicBlock *BB = BBs.pop_back_val();
// This random value acts as a block header, as otherwise the partition of
// opcodes into BBs wouldn't affect the hash, only the order of the opcodes
H.add(45798);
for (auto &Inst : *BB) {
H.add(Inst.getOpcode());
}
const TerminatorInst *Term = BB->getTerminator();
for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
continue;
BBs.push_back(Term->getSuccessor(i));
}
}
return H.getHash();
}
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), FnTree(FunctionNodeCmp(&GlobalNumbers)), FNodesInTree(),
HasGlobalAliases(false) {
initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override;
private:
// The function comparison operator is provided here so that FunctionNodes do
// not need to become larger with another pointer.
class FunctionNodeCmp {
GlobalNumberState* GlobalNumbers;
public:
FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
// Order first by hashes, then full function comparison.
if (LHS.getHash() != RHS.getHash())
return LHS.getHash() < RHS.getHash();
FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
return FCmp.compare() == -1;
}
};
typedef std::set<FunctionNode, FunctionNodeCmp> FnTreeType;
GlobalNumberState GlobalNumbers;
/// 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);
/// Replace function F with function G in the function tree.
void replaceFunctionInTree(const FunctionNode &FN, Function *G);
/// The set of all distinct functions. Use the insert() and remove() methods
/// to modify it. The map allows efficient lookup and deferring of Functions.
FnTreeType FnTree;
// Map functions to the iterators of the FunctionNode which contains them
// in the FnTree. This must be updated carefully whenever the FnTree is
// modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
// dangling iterators into FnTree. The invariant that preserves this is that
// there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
ValueMap<Function*, FnTreeType::iterator> FNodesInTree;
/// 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(F1, F2, &GlobalNumbers).compare();
int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).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(F1, F3, &GlobalNumbers).compare();
int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).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) {
if (skipModule(M))
return false;
bool Changed = false;
// All functions in the module, ordered by hash. Functions with a unique
// hash value are easily eliminated.
std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
HashedFuncs;
for (Function &Func : M) {
if (!Func.isDeclaration() && !Func.hasAvailableExternallyLinkage()) {
HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
}
}
std::stable_sort(
HashedFuncs.begin(), HashedFuncs.end(),
[](const std::pair<FunctionComparator::FunctionHash, Function *> &a,
const std::pair<FunctionComparator::FunctionHash, Function *> &b) {
return a.first < b.first;
});
auto S = HashedFuncs.begin();
for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
// If the hash value matches the previous value or the next one, we must
// consider merging it. Otherwise it is dropped and never considered again.
if ((I != S && std::prev(I)->first == I->first) ||
(std::next(I) != IE && std::next(I)->first == I->first) ) {
Deferred.push_back(WeakVH(I->second));
}
}
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 functions and merge 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()) {
Changed |= insert(F);
}
}
DEBUG(dbgs() << "size of FnTree: " << FnTree.size() << '\n');
} while (!Deferred.empty());
FnTree.clear();
GlobalNumbers.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)) {
// Transfer the called function's attributes to the call site. Due to the
// bitcast we will 'lose' ABI changing attributes because the 'called
// function' is no longer a Function* but the bitcast. Code that looks up
// the attributes from the called function will fail.
// FIXME: This is not actually true, at least not anymore. The callsite
// will always have the same ABI affecting attributes as the callee,
// because otherwise the original input has UB. Note that Old and New
// always have matching ABI, so no attributes need to be changed.
// Transferring other attributes may help other optimizations, but that
// should be done uniformly and not in this ad-hoc way.
auto &Context = New->getContext();
auto NewFuncAttrs = New->getAttributes();
auto CallSiteAttrs = CS.getAttributes();
CallSiteAttrs = CallSiteAttrs.addAttributes(
Context, AttributeSet::ReturnIndex, NewFuncAttrs.getRetAttributes());
for (unsigned argIdx = 0; argIdx < CS.arg_size(); argIdx++) {
AttributeSet Attrs = NewFuncAttrs.getParamAttributes(argIdx);
if (Attrs.getNumSlots())
CallSiteAttrs = CallSiteAttrs.addAttributes(Context, argIdx, Attrs);
}
CS.setAttributes(CallSiteAttrs);
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<> &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, makeArrayRef(I)),
DestTy->getStructElementType(I));
Result =
Builder.CreateInsertValue(Result, Element, makeArrayRef(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->isInterposable()) {
// 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<> Builder(BB);
SmallVector<Value *, 16> Args;
unsigned i = 0;
FunctionType *FFTy = F->getFunctionType();
for (Argument & AI : NewG->args()) {
Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
++i;
}
CallInst *CI = Builder.CreateCall(F, Args);
CI->setTailCall();
CI->setCallingConv(F->getCallingConv());
CI->setAttributes(F->getAttributes());
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) {
auto *GA = GlobalAlias::create(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->isInterposable()) {
assert(G->isInterposable());
// 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());
if (HasGlobalAliases) {
writeAlias(F, G);
writeAlias(F, H);
} else {
writeThunk(F, G);
writeThunk(F, H);
}
F->setAlignment(MaxAlignment);
F->setLinkage(GlobalValue::PrivateLinkage);
++NumDoubleWeak;
} else {
writeThunkOrAlias(F, G);
}
++NumFunctionsMerged;
}
/// Replace function F by function G.
void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
Function *G) {
Function *F = FN.getFunc();
assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&
"The two functions must be equal");
auto I = FNodesInTree.find(F);
assert(I != FNodesInTree.end() && "F should be in FNodesInTree");
assert(FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G");
FnTreeType::iterator IterToFNInFnTree = I->second;
assert(&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree.");
// Remove F -> FN and insert G -> FN
FNodesInTree.erase(I);
FNodesInTree.insert({G, IterToFNInFnTree});
// Replace F with G in FN, which is stored inside the FnTree.
FN.replaceBy(G);
}
// 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(FunctionNode(NewFunction));
if (Result.second) {
assert(FNodesInTree.count(NewFunction) == 0);
FNodesInTree.insert({NewFunction, Result.first});
DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName() << '\n');
return false;
}
const FunctionNode &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;
}
}
// Impose a total order (by name) on the replacement of functions. This is
// important when operating on more than one module independently to prevent
// cycles of thunks calling each other when the modules are linked together.
//
// First of all, we process strong functions before weak functions.
if ((OldF.getFunc()->isInterposable() && !NewFunction->isInterposable()) ||
(OldF.getFunc()->isInterposable() == NewFunction->isInterposable() &&
OldF.getFunc()->getName() > NewFunction->getName())) {
// Swap the two functions.
Function *F = OldF.getFunc();
replaceFunctionInTree(*Result.first, NewFunction);
NewFunction = F;
assert(OldF.getFunc() != F && "Must have swapped the functions.");
}
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) {
auto I = FNodesInTree.find(F);
if (I != FNodesInTree.end()) {
DEBUG(dbgs() << "Deferred " << F->getName()<< ".\n");
FnTree.erase(I->second);
// I->second has been invalidated, remove it from the FNodesInTree map to
// preserve the invariant.
FNodesInTree.erase(I);
Deferred.emplace_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);
SmallSet<Value*, 8> Visited;
Visited.insert(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()) {
if (!Visited.insert(UU).second)
Worklist.push_back(UU);
}
}
}
}
}
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