#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"
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;
+ }
+};
+
/// 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)
- : FnL(F1), FnR(F2) {}
+ 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();
private:
/// Test whether two basic blocks have equivalent behaviour.
- int compare(const BasicBlock *BBL, const BasicBlock *BBR);
+ int cmpBasicBlocks(const BasicBlock *BBL, const BasicBlock *BBR);
/// Constants comparison.
/// Its analog to lexicographical comparison between hypothetical numbers
/// If these properties are equal - compare their contents.
int cmpConstants(const Constant *L, const Constant *R);
+ /// Compares two global values by number. Uses the GlobalNumbersState to
+ /// identify the same gobals across function calls.
+ int cmpGlobalValues(GlobalValue *L, GlobalValue *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.
///
/// 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:
+ /// 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
/// * PPC_FP128
/// * Label
/// * Metadata
- /// If so - return 0, yes - we can treat these types as equal only because
- /// their IDs are same.
+ /// 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.
int cmpAPInts(const APInt &L, const APInt &R) const;
int cmpAPFloats(const APFloat &L, const APFloat &R) const;
- int cmpStrings(StringRef L, StringRef 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;
// The two functions undergoing comparison.
/// 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;
+
+ // 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)){}
+ 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 {
- assert(!(*this < FunctionNode(G)) && !(FunctionNode(G) < *this) &&
- "The two functions must be equal");
-
F = G;
}
void release() { F = 0; }
- bool operator<(const FunctionNode &RHS) const {
- // Order first by hashes, then full function comparison.
- if (Hash != RHS.Hash)
- return Hash < RHS.Hash;
- return (FunctionComparator(F, RHS.getFunc()).compare()) == -1;
- }
};
}
}
int FunctionComparator::cmpAPFloats(const APFloat &L, const APFloat &R) const {
- if (int Res = cmpNumbers((uint64_t)&L.getSemantics(),
- (uint64_t)&R.getSemantics()))
+ // TODO: This correctly handles all existing fltSemantics, because they all
+ // have different precisions. This isn't very robust, however, if new types
+ // with different exponent ranges are introduced.
+ const fltSemantics &SL = L.getSemantics(), &SR = R.getSemantics();
+ if (int Res = cmpNumbers(APFloat::semanticsPrecision(SL),
+ APFloat::semanticsPrecision(SR)))
return Res;
return cmpAPInts(L.bitcastToAPInt(), R.bitcastToAPInt());
}
-int FunctionComparator::cmpStrings(StringRef L, StringRef R) const {
+int FunctionComparator::cmpMem(StringRef L, StringRef R) const {
// Prevent heavy comparison, compare sizes first.
if (int Res = cmpNumbers(L.size(), R.size()))
return Res;
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 = dyn_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: return TypesRes;
case Value::ConstantIntVal: {
}
return 0;
}
- case Value::FunctionVal:
- case Value::GlobalVariableVal:
- case Value::GlobalAliasVal:
- default: // Unknown constant, cast L and R pointers to numbers and compare.
+ case Value::BlockAddressVal: {
+ // FIXME: This still uses a pointer comparison. It isn't clear how to remove
+ // this. This only affects programs which take BlockAddresses and store them
+ // as constants, which is limited to interepreters, etc.
return cmpNumbers((uint64_t)L, (uint64_t)R);
}
+ 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) {
+ return cmpNumbers(GlobalNumbers->getNumber(L), GlobalNumbers->getNumber(R));
}
/// cmpType - compares two types,
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);
-
+ 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:
if (GEPL->accumulateConstantOffset(DL, OffsetL) &&
GEPR->accumulateConstantOffset(DL, OffsetR))
return cmpAPInts(OffsetL, OffsetR);
-
- if (int Res = cmpNumbers((uint64_t)GEPL->getPointerOperand()->getType(),
- (uint64_t)GEPR->getPointerOperand()->getType()))
+ if (int Res = cmpTypes(GEPL->getPointerOperand()->getType(),
+ GEPR->getPointerOperand()->getType()))
return Res;
if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands()))
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.
const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
if (InlineAsmL && InlineAsmR)
- return cmpNumbers((uint64_t)L, (uint64_t)R);
+ return cmpInlineAsm(InlineAsmL, InlineAsmR);
if (InlineAsmL)
return 1;
if (InlineAsmR)
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) {
+int FunctionComparator::cmpBasicBlocks(const BasicBlock *BBL,
+ const BasicBlock *BBR) {
BasicBlock::const_iterator InstL = BBL->begin(), InstLE = BBL->end();
BasicBlock::const_iterator InstR = BBR->begin(), InstRE = BBR->end();
return Res;
if (FnL->hasGC()) {
- if (int Res = cmpNumbers((uint64_t)FnL->getGC(), (uint64_t)FnR->getGC()))
+ if (int Res = cmpMem(FnL->getGC(), FnR->getGC()))
return Res;
}
return Res;
if (FnL->hasSection()) {
- if (int Res = cmpStrings(FnL->getSection(), FnR->getSection()))
+ if (int Res = cmpMem(FnL->getSection(), FnR->getSection()))
return Res;
}
if (int Res = cmpValues(BBL, BBR))
return Res;
- if (int Res = compare(BBL, BBR))
+ if (int Res = cmpBasicBlocks(BBL, BBR))
return Res;
const TerminatorInst *TermL = BBL->getTerminator();
SmallVector<const BasicBlock *, 8> BBs;
SmallSet<const BasicBlock *, 16> VisitedBBs;
- // Walk the blocks in the same order as FunctionComparator::compare(),
+ // 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]);
public:
static char ID;
MergeFunctions()
- : ModulePass(ID), HasGlobalAliases(false) {
+ : ModulePass(ID), FnTree(FunctionNodeCmp(&GlobalNumbers)),
+ HasGlobalAliases(false) {
initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override;
private:
- typedef std::set<FunctionNode> FnTreeType;
+ // 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.
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).compare();
- int Res2 = FunctionComparator(F2, F1).compare();
+ 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) {
continue;
Function *F3 = cast<Function>(*K);
- int Res3 = FunctionComparator(F1, F3).compare();
- int Res4 = FunctionComparator(F2, F3).compare();
+ int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
+ int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
bool Transitive = true;
(!F->mayBeOverridden() && !G->mayBeOverridden())) &&
"Only change functions if both are strong or both are weak");
(void)F;
+ assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&
+ "The two functions must be equal");
IterToF->replaceBy(G);
}
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