X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FAnalysis%2FLazyValueInfo.cpp;h=0d1d34e0cb4fc1c221f15233e6ace2f06b46ec3a;hp=243cc26acb68ebd2665be3cade8d4ba9982c1a4b;hb=HEAD;hpb=f33b302e5bef8d7c71cbf6c6bb63776f067d3d89 diff --git a/lib/Analysis/LazyValueInfo.cpp b/lib/Analysis/LazyValueInfo.cpp index 243cc26acb6..0d1d34e0cb4 100644 --- a/lib/Analysis/LazyValueInfo.cpp +++ b/lib/Analysis/LazyValueInfo.cpp @@ -1,4 +1,4 @@ -//===- LazyValueInfo.cpp - Value constraint analysis ----------------------===// +//===- LazyValueInfo.cpp - Value constraint analysis ------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // @@ -12,26 +12,38 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "lazy-value-info" #include "llvm/Analysis/LazyValueInfo.h" -#include "llvm/Constants.h" -#include "llvm/Instructions.h" +#include "llvm/ADT/DenseSet.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/Analysis/AssumptionCache.h" #include "llvm/Analysis/ConstantFolding.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Support/CFG.h" -#include "llvm/Support/ConstantRange.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/ConstantRange.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/IR/ValueHandle.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" -#include "llvm/Support/ValueHandle.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/DenseSet.h" -#include "llvm/ADT/STLExtras.h" #include -#include +#include using namespace llvm; +using namespace PatternMatch; + +#define DEBUG_TYPE "lazy-value-info" char LazyValueInfo::ID = 0; -INITIALIZE_PASS(LazyValueInfo, "lazy-value-info", +INITIALIZE_PASS_BEGIN(LazyValueInfo, "lazy-value-info", + "Lazy Value Information Analysis", false, true) +INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) +INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) +INITIALIZE_PASS_END(LazyValueInfo, "lazy-value-info", "Lazy Value Information Analysis", false, true) namespace llvm { @@ -43,8 +55,7 @@ namespace llvm { // LVILatticeVal //===----------------------------------------------------------------------===// -/// LVILatticeVal - This is the information tracked by LazyValueInfo for each -/// value. +/// This is the information tracked by LazyValueInfo for each value. /// /// FIXME: This is basically just for bringup, this can be made a lot more rich /// in the future. @@ -52,44 +63,40 @@ namespace llvm { namespace { class LVILatticeVal { enum LatticeValueTy { - /// undefined - This LLVM Value has no known value yet. + /// This Value has no known value yet. undefined, - - /// constant - This LLVM Value has a specific constant value. + + /// This Value has a specific constant value. constant, - /// notconstant - This LLVM value is known to not have the specified value. + + /// This Value is known to not have the specified value. notconstant, - - /// constantrange + + /// The Value falls within this range. constantrange, - - /// overdefined - This instruction is not known to be constant, and we know - /// it has a value. + + /// This value is not known to be constant, and we know that it has a value. overdefined }; - + /// Val: This stores the current lattice value along with the Constant* for /// the constant if this is a 'constant' or 'notconstant' value. LatticeValueTy Tag; Constant *Val; ConstantRange Range; - + public: - LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {} + LVILatticeVal() : Tag(undefined), Val(nullptr), Range(1, true) {} static LVILatticeVal get(Constant *C) { LVILatticeVal Res; - if (ConstantInt *CI = dyn_cast(C)) - Res.markConstantRange(ConstantRange(CI->getValue(), CI->getValue()+1)); - else if (!isa(C)) + if (!isa(C)) Res.markConstant(C); return Res; } static LVILatticeVal getNot(Constant *C) { LVILatticeVal Res; - if (ConstantInt *CI = dyn_cast(C)) - Res.markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue())); - else + if (!isa(C)) Res.markNotConstant(C); return Res; } @@ -98,30 +105,35 @@ public: Res.markConstantRange(CR); return Res; } + static LVILatticeVal getOverdefined() { + LVILatticeVal Res; + Res.markOverdefined(); + return Res; + } bool isUndefined() const { return Tag == undefined; } bool isConstant() const { return Tag == constant; } bool isNotConstant() const { return Tag == notconstant; } bool isConstantRange() const { return Tag == constantrange; } bool isOverdefined() const { return Tag == overdefined; } - + Constant *getConstant() const { assert(isConstant() && "Cannot get the constant of a non-constant!"); return Val; } - + Constant *getNotConstant() const { assert(isNotConstant() && "Cannot get the constant of a non-notconstant!"); return Val; } - + ConstantRange getConstantRange() const { assert(isConstantRange() && "Cannot get the constant-range of a non-constant-range!"); return Range; } - - /// markOverdefined - Return true if this is a change in status. + + /// Return true if this is a change in status. bool markOverdefined() { if (isOverdefined()) return false; @@ -129,130 +141,144 @@ public: return true; } - /// markConstant - Return true if this is a change in status. + /// Return true if this is a change in status. bool markConstant(Constant *V) { - if (isConstant()) { - assert(getConstant() == V && "Marking constant with different value"); + assert(V && "Marking constant with NULL"); + if (ConstantInt *CI = dyn_cast(V)) + return markConstantRange(ConstantRange(CI->getValue())); + if (isa(V)) return false; - } - + + assert((!isConstant() || getConstant() == V) && + "Marking constant with different value"); assert(isUndefined()); Tag = constant; - assert(V && "Marking constant with NULL"); Val = V; return true; } - - /// markNotConstant - Return true if this is a change in status. + + /// Return true if this is a change in status. bool markNotConstant(Constant *V) { - if (isNotConstant()) { - assert(getNotConstant() == V && "Marking !constant with different value"); + assert(V && "Marking constant with NULL"); + if (ConstantInt *CI = dyn_cast(V)) + return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue())); + if (isa(V)) return false; - } - - if (isConstant()) - assert(getConstant() != V && "Marking not constant with different value"); - else - assert(isUndefined()); + assert((!isConstant() || getConstant() != V) && + "Marking constant !constant with same value"); + assert((!isNotConstant() || getNotConstant() == V) && + "Marking !constant with different value"); + assert(isUndefined() || isConstant()); Tag = notconstant; - assert(V && "Marking constant with NULL"); Val = V; return true; } - - /// markConstantRange - Return true if this is a change in status. + + /// Return true if this is a change in status. bool markConstantRange(const ConstantRange NewR) { if (isConstantRange()) { if (NewR.isEmptySet()) return markOverdefined(); - - bool changed = Range == NewR; + + bool changed = Range != NewR; Range = NewR; return changed; } - + assert(isUndefined()); if (NewR.isEmptySet()) return markOverdefined(); - + Tag = constantrange; Range = NewR; return true; } - - /// mergeIn - Merge the specified lattice value into this one, updating this + + /// Merge the specified lattice value into this one, updating this /// one and returning true if anything changed. - bool mergeIn(const LVILatticeVal &RHS) { + bool mergeIn(const LVILatticeVal &RHS, const DataLayout &DL) { if (RHS.isUndefined() || isOverdefined()) return false; if (RHS.isOverdefined()) return markOverdefined(); - if (RHS.isNotConstant()) { - if (isNotConstant()) { - if (getNotConstant() != RHS.getNotConstant() || - isa(getNotConstant()) || - isa(RHS.getNotConstant())) - return markOverdefined(); - return false; - } else if (isConstant()) { - if (getConstant() == RHS.getNotConstant() || - isa(RHS.getNotConstant()) || - isa(getConstant())) - return markOverdefined(); - return markNotConstant(RHS.getNotConstant()); - } else if (isConstantRange()) { - // FIXME: This could be made more precise. + if (isUndefined()) { + Tag = RHS.Tag; + Val = RHS.Val; + Range = RHS.Range; + return true; + } + + if (isConstant()) { + if (RHS.isConstant()) { + if (Val == RHS.Val) + return false; return markOverdefined(); } - - assert(isUndefined() && "Unexpected lattice"); - return markNotConstant(RHS.getNotConstant()); - } - - if (RHS.isConstantRange()) { - if (isConstantRange()) { - ConstantRange NewR = Range.unionWith(RHS.getConstantRange()); - if (NewR.isFullSet()) + + if (RHS.isNotConstant()) { + if (Val == RHS.Val) return markOverdefined(); - else - return markConstantRange(NewR); - } else if (!isUndefined()) { + + // Unless we can prove that the two Constants are different, we must + // move to overdefined. + if (ConstantInt *Res = + dyn_cast(ConstantFoldCompareInstOperands( + CmpInst::ICMP_NE, getConstant(), RHS.getNotConstant(), DL))) + if (Res->isOne()) + return markNotConstant(RHS.getNotConstant()); + return markOverdefined(); } - - assert(isUndefined() && "Unexpected lattice"); - return markConstantRange(RHS.getConstantRange()); - } - - // RHS must be a constant, we must be constantrange, - // undef, constant, or notconstant. - if (isConstantRange()) { - // FIXME: This could be made more precise. + + // RHS is a ConstantRange, LHS is a non-integer Constant. + + // FIXME: consider the case where RHS is a range [1, 0) and LHS is + // a function. The correct result is to pick up RHS. + return markOverdefined(); } - - if (isUndefined()) - return markConstant(RHS.getConstant()); - - if (isConstant()) { - if (getConstant() != RHS.getConstant()) + + if (isNotConstant()) { + if (RHS.isConstant()) { + if (Val == RHS.Val) + return markOverdefined(); + + // Unless we can prove that the two Constants are different, we must + // move to overdefined. + if (ConstantInt *Res = + dyn_cast(ConstantFoldCompareInstOperands( + CmpInst::ICMP_NE, getNotConstant(), RHS.getConstant(), DL))) + if (Res->isOne()) + return false; + return markOverdefined(); - return false; + } + + if (RHS.isNotConstant()) { + if (Val == RHS.Val) + return false; + return markOverdefined(); + } + + return markOverdefined(); } - // If we are known "!=4" and RHS is "==5", stay at "!=4". - if (getNotConstant() == RHS.getConstant() || - isa(getNotConstant()) || - isa(RHS.getConstant())) + assert(isConstantRange() && "New LVILattice type?"); + if (!RHS.isConstantRange()) return markOverdefined(); - return false; + + ConstantRange NewR = Range.unionWith(RHS.getConstantRange()); + if (NewR.isFullSet()) + return markOverdefined(); + return markConstantRange(NewR); } - }; - + } // end anonymous namespace. namespace llvm { +raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) + LLVM_ATTRIBUTE_USED; raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) { if (Val.isUndefined()) return OS << "undefined"; @@ -273,208 +299,305 @@ raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) { //===----------------------------------------------------------------------===// namespace { - /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which + /// A callback value handle updates the cache when values are erased. + class LazyValueInfoCache; + struct LVIValueHandle final : public CallbackVH { + LazyValueInfoCache *Parent; + + LVIValueHandle(Value *V, LazyValueInfoCache *P) + : CallbackVH(V), Parent(P) { } + + void deleted() override; + void allUsesReplacedWith(Value *V) override { + deleted(); + } + }; +} + +namespace { + /// This is the cache kept by LazyValueInfo which /// maintains information about queries across the clients' queries. class LazyValueInfoCache { - public: - /// ValueCacheEntryTy - This is all of the cached block information for - /// exactly one Value*. The entries are sorted by the BasicBlock* of the + /// This is all of the cached block information for exactly one Value*. + /// The entries are sorted by the BasicBlock* of the /// entries, allowing us to do a lookup with a binary search. - typedef std::map, LVILatticeVal> ValueCacheEntryTy; - - private: - /// LVIValueHandle - A callback value handle update the cache when - /// values are erased. - struct LVIValueHandle : public CallbackVH { - LazyValueInfoCache *Parent; - - LVIValueHandle(Value *V, LazyValueInfoCache *P) - : CallbackVH(V), Parent(P) { } - - void deleted(); - void allUsesReplacedWith(Value* V) { - deleted(); - } - }; + /// Over-defined lattice values are recorded in OverDefinedCache to reduce + /// memory overhead. + typedef SmallDenseMap, LVILatticeVal, 4> + ValueCacheEntryTy; - /// ValueCache - This is all of the cached information for all values, + /// This is all of the cached information for all values, /// mapped from Value* to key information. std::map ValueCache; - - /// OverDefinedCache - This tracks, on a per-block basis, the set of - /// values that are over-defined at the end of that block. This is required - /// for cache updating. - std::set, Value*> > OverDefinedCache; - LVILatticeVal &getCachedEntryForBlock(Value *Val, BasicBlock *BB); + /// This tracks, on a per-block basis, the set of values that are + /// over-defined at the end of that block. + typedef DenseMap, SmallPtrSet> + OverDefinedCacheTy; + OverDefinedCacheTy OverDefinedCache; + + /// Keep track of all blocks that we have ever seen, so we + /// don't spend time removing unused blocks from our caches. + DenseSet > SeenBlocks; + + /// This stack holds the state of the value solver during a query. + /// It basically emulates the callstack of the naive + /// recursive value lookup process. + std::stack > BlockValueStack; + + /// Keeps track of which block-value pairs are in BlockValueStack. + DenseSet > BlockValueSet; + + /// Push BV onto BlockValueStack unless it's already in there. + /// Returns true on success. + bool pushBlockValue(const std::pair &BV) { + if (!BlockValueSet.insert(BV).second) + return false; // It's already in the stack. + + BlockValueStack.push(BV); + return true; + } + + AssumptionCache *AC; ///< A pointer to the cache of @llvm.assume calls. + const DataLayout &DL; ///< A mandatory DataLayout + DominatorTree *DT; ///< An optional DT pointer. + + friend struct LVIValueHandle; + + void insertResult(Value *Val, BasicBlock *BB, const LVILatticeVal &Result) { + SeenBlocks.insert(BB); + + // Insert over-defined values into their own cache to reduce memory + // overhead. + if (Result.isOverdefined()) + OverDefinedCache[BB].insert(Val); + else + lookup(Val)[BB] = Result; + } + LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB); - LVILatticeVal getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T); - - ValueCacheEntryTy &lookup(Value *V) { + bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T, + LVILatticeVal &Result, + Instruction *CxtI = nullptr); + bool hasBlockValue(Value *Val, BasicBlock *BB); + + // These methods process one work item and may add more. A false value + // returned means that the work item was not completely processed and must + // be revisited after going through the new items. + bool solveBlockValue(Value *Val, BasicBlock *BB); + bool solveBlockValueNonLocal(LVILatticeVal &BBLV, + Value *Val, BasicBlock *BB); + bool solveBlockValuePHINode(LVILatticeVal &BBLV, + PHINode *PN, BasicBlock *BB); + bool solveBlockValueConstantRange(LVILatticeVal &BBLV, + Instruction *BBI, BasicBlock *BB); + void mergeAssumeBlockValueConstantRange(Value *Val, LVILatticeVal &BBLV, + Instruction *BBI); + + void solve(); + + ValueCacheEntryTy &lookup(Value *V) { return ValueCache[LVIValueHandle(V, this)]; } - - LVILatticeVal setBlockValue(Value *V, BasicBlock *BB, LVILatticeVal L, - ValueCacheEntryTy &Cache) { - if (L.isOverdefined()) OverDefinedCache.insert(std::make_pair(BB, V)); - return Cache[BB] = L; + + bool isOverdefined(Value *V, BasicBlock *BB) const { + auto ODI = OverDefinedCache.find(BB); + + if (ODI == OverDefinedCache.end()) + return false; + + return ODI->second.count(V); + } + + bool hasCachedValueInfo(Value *V, BasicBlock *BB) { + if (isOverdefined(V, BB)) + return true; + + LVIValueHandle ValHandle(V, this); + auto I = ValueCache.find(ValHandle); + if (I == ValueCache.end()) + return false; + + return I->second.count(BB); + } + + LVILatticeVal getCachedValueInfo(Value *V, BasicBlock *BB) { + if (isOverdefined(V, BB)) + return LVILatticeVal::getOverdefined(); + + return lookup(V)[BB]; } public: - - /// getValueInBlock - This is the query interface to determine the lattice + /// This is the query interface to determine the lattice /// value for the specified Value* at the end of the specified block. - LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB); + LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB, + Instruction *CxtI = nullptr); - /// getValueOnEdge - This is the query interface to determine the lattice + /// This is the query interface to determine the lattice + /// value for the specified Value* at the specified instruction (generally + /// from an assume intrinsic). + LVILatticeVal getValueAt(Value *V, Instruction *CxtI); + + /// This is the query interface to determine the lattice /// value for the specified Value* that is true on the specified edge. - LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB); - - /// threadEdge - This is the update interface to inform the cache that an - /// edge from PredBB to OldSucc has been threaded to be from PredBB to - /// NewSucc. + LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB, + Instruction *CxtI = nullptr); + + /// This is the update interface to inform the cache that an edge from + /// PredBB to OldSucc has been threaded to be from PredBB to NewSucc. void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc); - - /// eraseBlock - This is part of the update interface to inform the cache + + /// This is part of the update interface to inform the cache /// that a block has been deleted. void eraseBlock(BasicBlock *BB); - + /// clear - Empty the cache. void clear() { + SeenBlocks.clear(); ValueCache.clear(); OverDefinedCache.clear(); } + + LazyValueInfoCache(AssumptionCache *AC, const DataLayout &DL, + DominatorTree *DT = nullptr) + : AC(AC), DL(DL), DT(DT) {} }; } // end anonymous namespace -void LazyValueInfoCache::LVIValueHandle::deleted() { - for (std::set, Value*> >::iterator - I = Parent->OverDefinedCache.begin(), - E = Parent->OverDefinedCache.end(); - I != E; ) { - std::set, Value*> >::iterator tmp = I; - ++I; - if (tmp->second == getValPtr()) - Parent->OverDefinedCache.erase(tmp); +void LVIValueHandle::deleted() { + SmallVector, 4> ToErase; + for (auto &I : Parent->OverDefinedCache) { + SmallPtrSetImpl &ValueSet = I.second; + if (ValueSet.count(getValPtr())) + ValueSet.erase(getValPtr()); + if (ValueSet.empty()) + ToErase.push_back(I.first); } - + for (auto &BB : ToErase) + Parent->OverDefinedCache.erase(BB); + // This erasure deallocates *this, so it MUST happen after we're done // using any and all members of *this. Parent->ValueCache.erase(*this); } void LazyValueInfoCache::eraseBlock(BasicBlock *BB) { - for (std::set, Value*> >::iterator - I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) { - std::set, Value*> >::iterator tmp = I; - ++I; - if (tmp->first == BB) - OverDefinedCache.erase(tmp); - } + // Shortcut if we have never seen this block. + DenseSet >::iterator I = SeenBlocks.find(BB); + if (I == SeenBlocks.end()) + return; + SeenBlocks.erase(I); - for (std::map::iterator - I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I) + auto ODI = OverDefinedCache.find(BB); + if (ODI != OverDefinedCache.end()) + OverDefinedCache.erase(ODI); + + for (auto I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I) I->second.erase(BB); } +void LazyValueInfoCache::solve() { + while (!BlockValueStack.empty()) { + std::pair &e = BlockValueStack.top(); + assert(BlockValueSet.count(e) && "Stack value should be in BlockValueSet!"); + + if (solveBlockValue(e.second, e.first)) { + // The work item was completely processed. + assert(BlockValueStack.top() == e && "Nothing should have been pushed!"); + assert(hasCachedValueInfo(e.second, e.first) && + "Result should be in cache!"); + + BlockValueStack.pop(); + BlockValueSet.erase(e); + } else { + // More work needs to be done before revisiting. + assert(BlockValueStack.top() != e && "Stack should have been pushed!"); + } + } +} + +bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) { + // If already a constant, there is nothing to compute. + if (isa(Val)) + return true; + + return hasCachedValueInfo(Val, BB); +} + LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) { - ValueCacheEntryTy &Cache = lookup(Val); - LVILatticeVal &BBLV = Cache[BB]; - - // If we've already computed this block's value, return it. - if (!BBLV.isUndefined()) { - DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n'); - return BBLV; + // If already a constant, there is nothing to compute. + if (Constant *VC = dyn_cast(Val)) + return LVILatticeVal::get(VC); + + SeenBlocks.insert(BB); + return getCachedValueInfo(Val, BB); +} + +static LVILatticeVal getFromRangeMetadata(Instruction *BBI) { + switch (BBI->getOpcode()) { + default: break; + case Instruction::Load: + case Instruction::Call: + case Instruction::Invoke: + if (MDNode *Ranges = BBI->getMetadata(LLVMContext::MD_range)) + if (isa(BBI->getType())) { + ConstantRange Result = getConstantRangeFromMetadata(*Ranges); + return LVILatticeVal::getRange(Result); + } + break; + }; + // Nothing known - Note that we do not want overdefined here. We may know + // something else about the value and not having range metadata shouldn't + // cause us to throw away those facts. + return LVILatticeVal(); +} + +bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) { + if (isa(Val)) + return true; + + if (hasCachedValueInfo(Val, BB)) { + // If we have a cached value, use that. + DEBUG(dbgs() << " reuse BB '" << BB->getName() + << "' val=" << getCachedValueInfo(Val, BB) << '\n'); + + // Since we're reusing a cached value, we don't need to update the + // OverDefinedCache. The cache will have been properly updated whenever the + // cached value was inserted. + return true; } - // Otherwise, this is the first time we're seeing this block. Reset the - // lattice value to overdefined, so that cycles will terminate and be - // conservatively correct. - BBLV.markOverdefined(); - + // Hold off inserting this value into the Cache in case we have to return + // false and come back later. + LVILatticeVal Res; + Instruction *BBI = dyn_cast(Val); - if (BBI == 0 || BBI->getParent() != BB) { - LVILatticeVal Result; // Start Undefined. - - // If this is a pointer, and there's a load from that pointer in this BB, - // then we know that the pointer can't be NULL. - bool NotNull = false; - if (Val->getType()->isPointerTy()) { - for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){ - LoadInst *L = dyn_cast(BI); - if (L && L->getPointerAddressSpace() == 0 && - L->getPointerOperand()->getUnderlyingObject() == - Val->getUnderlyingObject()) { - NotNull = true; - break; - } - } - } - - unsigned NumPreds = 0; - // Loop over all of our predecessors, merging what we know from them into - // result. - for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { - Result.mergeIn(getEdgeValue(Val, *PI, BB)); - - // If we hit overdefined, exit early. The BlockVals entry is already set - // to overdefined. - if (Result.isOverdefined()) { - DEBUG(dbgs() << " compute BB '" << BB->getName() - << "' - overdefined because of pred.\n"); - // If we previously determined that this is a pointer that can't be null - // then return that rather than giving up entirely. - if (NotNull) { - const PointerType *PTy = cast(Val->getType()); - Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy)); - } - - return setBlockValue(Val, BB, Result, Cache); - } - ++NumPreds; - } - - - // If this is the entry block, we must be asking about an argument. The - // value is overdefined. - if (NumPreds == 0 && BB == &BB->getParent()->front()) { - assert(isa(Val) && "Unknown live-in to the entry block"); - Result.markOverdefined(); - return setBlockValue(Val, BB, Result, Cache); - } - - // Return the merged value, which is more precise than 'overdefined'. - assert(!Result.isOverdefined()); - return setBlockValue(Val, BB, Result, Cache); + if (!BBI || BBI->getParent() != BB) { + if (!solveBlockValueNonLocal(Res, Val, BB)) + return false; + insertResult(Val, BB, Res); + return true; } - - // If this value is defined by an instruction in this block, we have to - // process it here somehow or return overdefined. + if (PHINode *PN = dyn_cast(BBI)) { - LVILatticeVal Result; // Start Undefined. - - // Loop over all of our predecessors, merging what we know from them into - // result. - for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { - Value* PhiVal = PN->getIncomingValueForBlock(*PI); - Result.mergeIn(getValueOnEdge(PhiVal, *PI, BB)); - - // If we hit overdefined, exit early. The BlockVals entry is already set - // to overdefined. - if (Result.isOverdefined()) { - DEBUG(dbgs() << " compute BB '" << BB->getName() - << "' - overdefined because of pred.\n"); - return setBlockValue(Val, BB, Result, Cache); - } - } - - // Return the merged value, which is more precise than 'overdefined'. - assert(!Result.isOverdefined()); - return setBlockValue(Val, BB, Result, Cache); + if (!solveBlockValuePHINode(Res, PN, BB)) + return false; + insertResult(Val, BB, Res); + return true; + } + + // If this value is a nonnull pointer, record it's range and bailout. + PointerType *PT = dyn_cast(BBI->getType()); + if (PT && isKnownNonNull(BBI)) { + Res = LVILatticeVal::getNot(ConstantPointerNull::get(PT)); + insertResult(Val, BB, Res); + return true; } - assert(Cache[BB].isOverdefined() && - "Recursive query changed our cache?"); + // If this is an instruction which supports range metadata, return the + // implied range. TODO: This should be an intersection, not a union. + Res.mergeIn(getFromRangeMetadata(BBI), DL); // We can only analyze the definitions of certain classes of instructions // (integral binops and casts at the moment), so bail if this isn't one. @@ -483,10 +606,11 @@ LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) { !BBI->getType()->isIntegerTy()) { DEBUG(dbgs() << " compute BB '" << BB->getName() << "' - overdefined because inst def found.\n"); - Result.markOverdefined(); - return setBlockValue(Val, BB, Result, Cache); + Res.markOverdefined(); + insertResult(Val, BB, Res); + return true; } - + // FIXME: We're currently limited to binops with a constant RHS. This should // be improved. BinaryOperator *BO = dyn_cast(BBI); @@ -494,34 +618,231 @@ LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) { DEBUG(dbgs() << " compute BB '" << BB->getName() << "' - overdefined because inst def found.\n"); - Result.markOverdefined(); - return setBlockValue(Val, BB, Result, Cache); - } + Res.markOverdefined(); + insertResult(Val, BB, Res); + return true; + } + + if (!solveBlockValueConstantRange(Res, BBI, BB)) + return false; + insertResult(Val, BB, Res); + return true; +} + +static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) { + if (LoadInst *L = dyn_cast(I)) { + return L->getPointerAddressSpace() == 0 && + GetUnderlyingObject(L->getPointerOperand(), + L->getModule()->getDataLayout()) == Ptr; + } + if (StoreInst *S = dyn_cast(I)) { + return S->getPointerAddressSpace() == 0 && + GetUnderlyingObject(S->getPointerOperand(), + S->getModule()->getDataLayout()) == Ptr; + } + if (MemIntrinsic *MI = dyn_cast(I)) { + if (MI->isVolatile()) return false; + + // FIXME: check whether it has a valuerange that excludes zero? + ConstantInt *Len = dyn_cast(MI->getLength()); + if (!Len || Len->isZero()) return false; + + if (MI->getDestAddressSpace() == 0) + if (GetUnderlyingObject(MI->getRawDest(), + MI->getModule()->getDataLayout()) == Ptr) + return true; + if (MemTransferInst *MTI = dyn_cast(MI)) + if (MTI->getSourceAddressSpace() == 0) + if (GetUnderlyingObject(MTI->getRawSource(), + MTI->getModule()->getDataLayout()) == Ptr) + return true; + } + return false; +} + +bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV, + Value *Val, BasicBlock *BB) { + LVILatticeVal Result; // Start Undefined. + + // If this is a pointer, and there's a load from that pointer in this BB, + // then we know that the pointer can't be NULL. + bool NotNull = false; + if (Val->getType()->isPointerTy()) { + if (isKnownNonNull(Val)) { + NotNull = true; + } else { + const DataLayout &DL = BB->getModule()->getDataLayout(); + Value *UnderlyingVal = GetUnderlyingObject(Val, DL); + // If 'GetUnderlyingObject' didn't converge, skip it. It won't converge + // inside InstructionDereferencesPointer either. + if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, DL, 1)) { + for (Instruction &I : *BB) { + if (InstructionDereferencesPointer(&I, UnderlyingVal)) { + NotNull = true; + break; + } + } + } + } + } + + // If this is the entry block, we must be asking about an argument. The + // value is overdefined. + if (BB == &BB->getParent()->getEntryBlock()) { + assert(isa(Val) && "Unknown live-in to the entry block"); + if (NotNull) { + PointerType *PTy = cast(Val->getType()); + Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy)); + } else { + Result.markOverdefined(); + } + BBLV = Result; + return true; + } + + // Loop over all of our predecessors, merging what we know from them into + // result. + bool EdgesMissing = false; + for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { + LVILatticeVal EdgeResult; + EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult); + if (EdgesMissing) + continue; + + Result.mergeIn(EdgeResult, DL); + + // If we hit overdefined, exit early. The BlockVals entry is already set + // to overdefined. + if (Result.isOverdefined()) { + DEBUG(dbgs() << " compute BB '" << BB->getName() + << "' - overdefined because of pred.\n"); + // If we previously determined that this is a pointer that can't be null + // then return that rather than giving up entirely. + if (NotNull) { + PointerType *PTy = cast(Val->getType()); + Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy)); + } + + BBLV = Result; + return true; + } + } + if (EdgesMissing) + return false; + + // Return the merged value, which is more precise than 'overdefined'. + assert(!Result.isOverdefined()); + BBLV = Result; + return true; +} + +bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV, + PHINode *PN, BasicBlock *BB) { + LVILatticeVal Result; // Start Undefined. + + // Loop over all of our predecessors, merging what we know from them into + // result. + bool EdgesMissing = false; + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + BasicBlock *PhiBB = PN->getIncomingBlock(i); + Value *PhiVal = PN->getIncomingValue(i); + LVILatticeVal EdgeResult; + // Note that we can provide PN as the context value to getEdgeValue, even + // though the results will be cached, because PN is the value being used as + // the cache key in the caller. + EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult, PN); + if (EdgesMissing) + continue; + + Result.mergeIn(EdgeResult, DL); + + // If we hit overdefined, exit early. The BlockVals entry is already set + // to overdefined. + if (Result.isOverdefined()) { + DEBUG(dbgs() << " compute BB '" << BB->getName() + << "' - overdefined because of pred.\n"); + + BBLV = Result; + return true; + } + } + if (EdgesMissing) + return false; + + // Return the merged value, which is more precise than 'overdefined'. + assert(!Result.isOverdefined() && "Possible PHI in entry block?"); + BBLV = Result; + return true; +} + +static bool getValueFromFromCondition(Value *Val, ICmpInst *ICI, + LVILatticeVal &Result, + bool isTrueDest = true); + +// If we can determine a constant range for the value Val in the context +// provided by the instruction BBI, then merge it into BBLV. If we did find a +// constant range, return true. +void LazyValueInfoCache::mergeAssumeBlockValueConstantRange(Value *Val, + LVILatticeVal &BBLV, + Instruction *BBI) { + BBI = BBI ? BBI : dyn_cast(Val); + if (!BBI) + return; + + for (auto &AssumeVH : AC->assumptions()) { + if (!AssumeVH) + continue; + auto *I = cast(AssumeVH); + if (!isValidAssumeForContext(I, BBI, DT)) + continue; + Value *C = I->getArgOperand(0); + if (ICmpInst *ICI = dyn_cast(C)) { + LVILatticeVal Result; + if (getValueFromFromCondition(Val, ICI, Result)) { + if (BBLV.isOverdefined()) + BBLV = Result; + else + BBLV.mergeIn(Result, DL); + } + } + } +} + +bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV, + Instruction *BBI, + BasicBlock *BB) { // Figure out the range of the LHS. If that fails, bail. - LVILatticeVal LHSVal = getValueInBlock(BBI->getOperand(0), BB); + if (!hasBlockValue(BBI->getOperand(0), BB)) { + if (pushBlockValue(std::make_pair(BB, BBI->getOperand(0)))) + return false; + BBLV.markOverdefined(); + return true; + } + + LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB); + mergeAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI); if (!LHSVal.isConstantRange()) { - Result.markOverdefined(); - return setBlockValue(Val, BB, Result, Cache); + BBLV.markOverdefined(); + return true; } - - ConstantInt *RHS = 0; + ConstantRange LHSRange = LHSVal.getConstantRange(); ConstantRange RHSRange(1); - const IntegerType *ResultTy = cast(BBI->getType()); + IntegerType *ResultTy = cast(BBI->getType()); if (isa(BBI)) { - RHS = dyn_cast(BBI->getOperand(1)); - if (!RHS) { - Result.markOverdefined(); - return setBlockValue(Val, BB, Result, Cache); + if (ConstantInt *RHS = dyn_cast(BBI->getOperand(1))) { + RHSRange = ConstantRange(RHS->getValue()); + } else { + BBLV.markOverdefined(); + return true; } - - RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1); } - + // NOTE: We're currently limited by the set of operations that ConstantRange // can evaluate symbolically. Enhancing that set will allows us to analyze // more definitions. + LVILatticeVal Result; switch (BBI->getOpcode()) { case Instruction::Add: Result.markConstantRange(LHSRange.add(RHSRange)); @@ -559,7 +880,7 @@ LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) { case Instruction::Or: Result.markConstantRange(LHSRange.binaryOr(RHSRange)); break; - + // Unhandled instructions are overdefined. default: DEBUG(dbgs() << " compute BB '" << BB->getName() @@ -567,152 +888,239 @@ LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) { Result.markOverdefined(); break; } - - return setBlockValue(Val, BB, Result, Cache); + + BBLV = Result; + return true; } +bool getValueFromFromCondition(Value *Val, ICmpInst *ICI, + LVILatticeVal &Result, bool isTrueDest) { + if (ICI && isa(ICI->getOperand(1))) { + if (ICI->isEquality() && ICI->getOperand(0) == Val) { + // We know that V has the RHS constant if this is a true SETEQ or + // false SETNE. + if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ)) + Result = LVILatticeVal::get(cast(ICI->getOperand(1))); + else + Result = LVILatticeVal::getNot(cast(ICI->getOperand(1))); + return true; + } + + // Recognize the range checking idiom that InstCombine produces. + // (X-C1) u< C2 --> [C1, C1+C2) + ConstantInt *NegOffset = nullptr; + if (ICI->getPredicate() == ICmpInst::ICMP_ULT) + match(ICI->getOperand(0), m_Add(m_Specific(Val), + m_ConstantInt(NegOffset))); + + ConstantInt *CI = dyn_cast(ICI->getOperand(1)); + if (CI && (ICI->getOperand(0) == Val || NegOffset)) { + // Calculate the range of values that are allowed by the comparison + ConstantRange CmpRange(CI->getValue()); + ConstantRange TrueValues = + ConstantRange::makeAllowedICmpRegion(ICI->getPredicate(), CmpRange); + + if (NegOffset) // Apply the offset from above. + TrueValues = TrueValues.subtract(NegOffset->getValue()); -/// getEdgeValue - This method attempts to infer more complex -LVILatticeVal LazyValueInfoCache::getEdgeValue(Value *Val, - BasicBlock *BBFrom, - BasicBlock *BBTo) { - // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we + // If we're interested in the false dest, invert the condition. + if (!isTrueDest) TrueValues = TrueValues.inverse(); + + Result = LVILatticeVal::getRange(TrueValues); + return true; + } + } + + return false; +} + +/// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if +/// Val is not constrained on the edge. +static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom, + BasicBlock *BBTo, LVILatticeVal &Result) { + // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we // know that v != 0. if (BranchInst *BI = dyn_cast(BBFrom->getTerminator())) { // If this is a conditional branch and only one successor goes to BBTo, then - // we maybe able to infer something from the condition. + // we may be able to infer something from the condition. if (BI->isConditional() && BI->getSuccessor(0) != BI->getSuccessor(1)) { bool isTrueDest = BI->getSuccessor(0) == BBTo; assert(BI->getSuccessor(!isTrueDest) == BBTo && "BBTo isn't a successor of BBFrom"); - + // If V is the condition of the branch itself, then we know exactly what // it is. - if (BI->getCondition() == Val) - return LVILatticeVal::get(ConstantInt::get( + if (BI->getCondition() == Val) { + Result = LVILatticeVal::get(ConstantInt::get( Type::getInt1Ty(Val->getContext()), isTrueDest)); - + return true; + } + // If the condition of the branch is an equality comparison, we may be // able to infer the value. - ICmpInst *ICI = dyn_cast(BI->getCondition()); - if (ICI && ICI->getOperand(0) == Val && - isa(ICI->getOperand(1))) { - if (ICI->isEquality()) { - // We know that V has the RHS constant if this is a true SETEQ or - // false SETNE. - if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ)) - return LVILatticeVal::get(cast(ICI->getOperand(1))); - return LVILatticeVal::getNot(cast(ICI->getOperand(1))); - } - - if (ConstantInt *CI = dyn_cast(ICI->getOperand(1))) { - // Calculate the range of values that would satisfy the comparison. - ConstantRange CmpRange(CI->getValue(), CI->getValue()+1); - ConstantRange TrueValues = - ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange); - - // If we're interested in the false dest, invert the condition. - if (!isTrueDest) TrueValues = TrueValues.inverse(); - - // Figure out the possible values of the query BEFORE this branch. - LVILatticeVal InBlock = getBlockValue(Val, BBFrom); - if (!InBlock.isConstantRange()) - return LVILatticeVal::getRange(TrueValues); - - // Find all potential values that satisfy both the input and output - // conditions. - ConstantRange PossibleValues = - TrueValues.intersectWith(InBlock.getConstantRange()); - - return LVILatticeVal::getRange(PossibleValues); - } - } + if (ICmpInst *ICI = dyn_cast(BI->getCondition())) + if (getValueFromFromCondition(Val, ICI, Result, isTrueDest)) + return true; } } // If the edge was formed by a switch on the value, then we may know exactly // what it is. if (SwitchInst *SI = dyn_cast(BBFrom->getTerminator())) { - if (SI->getCondition() == Val) { - // We don't know anything in the default case. - if (SI->getDefaultDest() == BBTo) { - LVILatticeVal Result; - Result.markOverdefined(); - return Result; - } - - // We only know something if there is exactly one value that goes from - // BBFrom to BBTo. - unsigned NumEdges = 0; - ConstantInt *EdgeVal = 0; - for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) { - if (SI->getSuccessor(i) != BBTo) continue; - if (NumEdges++) break; - EdgeVal = SI->getCaseValue(i); - } - assert(EdgeVal && "Missing successor?"); - if (NumEdges == 1) - return LVILatticeVal::get(EdgeVal); + if (SI->getCondition() != Val) + return false; + + bool DefaultCase = SI->getDefaultDest() == BBTo; + unsigned BitWidth = Val->getType()->getIntegerBitWidth(); + ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/); + + for (SwitchInst::CaseIt i : SI->cases()) { + ConstantRange EdgeVal(i.getCaseValue()->getValue()); + if (DefaultCase) { + // It is possible that the default destination is the destination of + // some cases. There is no need to perform difference for those cases. + if (i.getCaseSuccessor() != BBTo) + EdgesVals = EdgesVals.difference(EdgeVal); + } else if (i.getCaseSuccessor() == BBTo) + EdgesVals = EdgesVals.unionWith(EdgeVal); } + Result = LVILatticeVal::getRange(EdgesVals); + return true; } - - // Otherwise see if the value is known in the block. - return getBlockValue(Val, BBFrom); + return false; } -LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) { +/// \brief Compute the value of Val on the edge BBFrom -> BBTo or the value at +/// the basic block if the edge does not constrain Val. +bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom, + BasicBlock *BBTo, LVILatticeVal &Result, + Instruction *CxtI) { // If already a constant, there is nothing to compute. - if (Constant *VC = dyn_cast(V)) - return LVILatticeVal::get(VC); - + if (Constant *VC = dyn_cast(Val)) { + Result = LVILatticeVal::get(VC); + return true; + } + + if (getEdgeValueLocal(Val, BBFrom, BBTo, Result)) { + if (!Result.isConstantRange() || + Result.getConstantRange().getSingleElement()) + return true; + + // FIXME: this check should be moved to the beginning of the function when + // LVI better supports recursive values. Even for the single value case, we + // can intersect to detect dead code (an empty range). + if (!hasBlockValue(Val, BBFrom)) { + if (pushBlockValue(std::make_pair(BBFrom, Val))) + return false; + Result.markOverdefined(); + return true; + } + + // Try to intersect ranges of the BB and the constraint on the edge. + LVILatticeVal InBlock = getBlockValue(Val, BBFrom); + mergeAssumeBlockValueConstantRange(Val, InBlock, BBFrom->getTerminator()); + // See note on the use of the CxtI with mergeAssumeBlockValueConstantRange, + // and caching, below. + mergeAssumeBlockValueConstantRange(Val, InBlock, CxtI); + if (!InBlock.isConstantRange()) + return true; + + ConstantRange Range = + Result.getConstantRange().intersectWith(InBlock.getConstantRange()); + Result = LVILatticeVal::getRange(Range); + return true; + } + + if (!hasBlockValue(Val, BBFrom)) { + if (pushBlockValue(std::make_pair(BBFrom, Val))) + return false; + Result.markOverdefined(); + return true; + } + + // If we couldn't compute the value on the edge, use the value from the BB. + Result = getBlockValue(Val, BBFrom); + mergeAssumeBlockValueConstantRange(Val, Result, BBFrom->getTerminator()); + // We can use the context instruction (generically the ultimate instruction + // the calling pass is trying to simplify) here, even though the result of + // this function is generally cached when called from the solve* functions + // (and that cached result might be used with queries using a different + // context instruction), because when this function is called from the solve* + // functions, the context instruction is not provided. When called from + // LazyValueInfoCache::getValueOnEdge, the context instruction is provided, + // but then the result is not cached. + mergeAssumeBlockValueConstantRange(Val, Result, CxtI); + return true; +} + +LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB, + Instruction *CxtI) { DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '" << BB->getName() << "'\n"); - + + assert(BlockValueStack.empty() && BlockValueSet.empty()); + pushBlockValue(std::make_pair(BB, V)); + + solve(); LVILatticeVal Result = getBlockValue(V, BB); - + mergeAssumeBlockValueConstantRange(V, Result, CxtI); + + DEBUG(dbgs() << " Result = " << Result << "\n"); + return Result; +} + +LVILatticeVal LazyValueInfoCache::getValueAt(Value *V, Instruction *CxtI) { + DEBUG(dbgs() << "LVI Getting value " << *V << " at '" + << CxtI->getName() << "'\n"); + + LVILatticeVal Result; + if (auto *I = dyn_cast(V)) + Result = getFromRangeMetadata(I); + mergeAssumeBlockValueConstantRange(V, Result, CxtI); + DEBUG(dbgs() << " Result = " << Result << "\n"); return Result; } LVILatticeVal LazyValueInfoCache:: -getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) { - // If already a constant, there is nothing to compute. - if (Constant *VC = dyn_cast(V)) - return LVILatticeVal::get(VC); - +getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB, + Instruction *CxtI) { DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '" << FromBB->getName() << "' to '" << ToBB->getName() << "'\n"); - - LVILatticeVal Result = getEdgeValue(V, FromBB, ToBB); - + + LVILatticeVal Result; + if (!getEdgeValue(V, FromBB, ToBB, Result, CxtI)) { + solve(); + bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result, CxtI); + (void)WasFastQuery; + assert(WasFastQuery && "More work to do after problem solved?"); + } + DEBUG(dbgs() << " Result = " << Result << "\n"); - return Result; } void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, BasicBlock *NewSucc) { - // When an edge in the graph has been threaded, values that we could not - // determine a value for before (i.e. were marked overdefined) may be possible - // to solve now. We do NOT try to proactively update these values. Instead, - // we clear their entries from the cache, and allow lazy updating to recompute - // them when needed. - - // The updating process is fairly simple: we need to dropped cached info + // When an edge in the graph has been threaded, values that we could not + // determine a value for before (i.e. were marked overdefined) may be + // possible to solve now. We do NOT try to proactively update these values. + // Instead, we clear their entries from the cache, and allow lazy updating to + // recompute them when needed. + + // The updating process is fairly simple: we need to drop cached info // for all values that were marked overdefined in OldSucc, and for those same // values in any successor of OldSucc (except NewSucc) in which they were // also marked overdefined. std::vector worklist; worklist.push_back(OldSucc); - - DenseSet ClearSet; - for (std::set, Value*> >::iterator - I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) { - if (I->first == OldSucc) - ClearSet.insert(I->second); - } - + + auto I = OverDefinedCache.find(OldSucc); + if (I == OverDefinedCache.end()) + return; // Nothing to process here. + SmallVector ValsToClear(I->second.begin(), I->second.end()); + // Use a worklist to perform a depth-first search of OldSucc's successors. // NOTE: We do not need a visited list since any blocks we have already // visited will have had their overdefined markers cleared already, and we @@ -720,33 +1128,31 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, while (!worklist.empty()) { BasicBlock *ToUpdate = worklist.back(); worklist.pop_back(); - + // Skip blocks only accessible through NewSucc. if (ToUpdate == NewSucc) continue; - + bool changed = false; - for (DenseSet::iterator I = ClearSet.begin(),E = ClearSet.end(); - I != E; ++I) { + for (Value *V : ValsToClear) { // If a value was marked overdefined in OldSucc, and is here too... - std::set, Value*> >::iterator OI = - OverDefinedCache.find(std::make_pair(ToUpdate, *I)); - if (OI == OverDefinedCache.end()) continue; - - // Remove it from the caches. - ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)]; - ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate); - - assert(CI != Entry.end() && "Couldn't find entry to update?"); - Entry.erase(CI); - OverDefinedCache.erase(OI); - - // If we removed anything, then we potentially need to update + auto OI = OverDefinedCache.find(ToUpdate); + if (OI == OverDefinedCache.end()) + continue; + SmallPtrSetImpl &ValueSet = OI->second; + if (!ValueSet.count(V)) + continue; + + ValueSet.erase(V); + if (ValueSet.empty()) + OverDefinedCache.erase(OI); + + // If we removed anything, then we potentially need to update // blocks successors too. changed = true; } - + if (!changed) continue; - + worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate)); } } @@ -755,133 +1161,265 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, // LazyValueInfo Impl //===----------------------------------------------------------------------===// -/// getCache - This lazily constructs the LazyValueInfoCache. -static LazyValueInfoCache &getCache(void *&PImpl) { - if (!PImpl) - PImpl = new LazyValueInfoCache(); +/// This lazily constructs the LazyValueInfoCache. +static LazyValueInfoCache &getCache(void *&PImpl, AssumptionCache *AC, + const DataLayout *DL, + DominatorTree *DT = nullptr) { + if (!PImpl) { + assert(DL && "getCache() called with a null DataLayout"); + PImpl = new LazyValueInfoCache(AC, *DL, DT); + } return *static_cast(PImpl); } bool LazyValueInfo::runOnFunction(Function &F) { + AC = &getAnalysis().getAssumptionCache(F); + const DataLayout &DL = F.getParent()->getDataLayout(); + + DominatorTreeWrapperPass *DTWP = + getAnalysisIfAvailable(); + DT = DTWP ? &DTWP->getDomTree() : nullptr; + + TLI = &getAnalysis().getTLI(); + if (PImpl) - getCache(PImpl).clear(); - - TD = getAnalysisIfAvailable(); + getCache(PImpl, AC, &DL, DT).clear(); + // Fully lazy. return false; } +void LazyValueInfo::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequired(); + AU.addRequired(); +} + void LazyValueInfo::releaseMemory() { // If the cache was allocated, free it. if (PImpl) { - delete &getCache(PImpl); - PImpl = 0; + delete &getCache(PImpl, AC, nullptr); + PImpl = nullptr; } } -Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) { - LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB); - +Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB, + Instruction *CxtI) { + const DataLayout &DL = BB->getModule()->getDataLayout(); + LVILatticeVal Result = + getCache(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI); + if (Result.isConstant()) return Result.getConstant(); - else if (Result.isConstantRange()) { + if (Result.isConstantRange()) { ConstantRange CR = Result.getConstantRange(); if (const APInt *SingleVal = CR.getSingleElement()) return ConstantInt::get(V->getContext(), *SingleVal); } - return 0; + return nullptr; } -/// getConstantOnEdge - Determine whether the specified value is known to be a -/// constant on the specified edge. Return null if not. +/// Determine whether the specified value is known to be a +/// constant on the specified edge. Return null if not. Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB, - BasicBlock *ToBB) { - LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB); - + BasicBlock *ToBB, + Instruction *CxtI) { + const DataLayout &DL = FromBB->getModule()->getDataLayout(); + LVILatticeVal Result = + getCache(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI); + if (Result.isConstant()) return Result.getConstant(); - else if (Result.isConstantRange()) { + if (Result.isConstantRange()) { ConstantRange CR = Result.getConstantRange(); if (const APInt *SingleVal = CR.getSingleElement()) return ConstantInt::get(V->getContext(), *SingleVal); } - return 0; + return nullptr; } -/// getPredicateOnEdge - Determine whether the specified value comparison -/// with a constant is known to be true or false on the specified CFG edge. -/// Pred is a CmpInst predicate. -LazyValueInfo::Tristate -LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C, - BasicBlock *FromBB, BasicBlock *ToBB) { - LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB); - +static LazyValueInfo::Tristate getPredicateResult(unsigned Pred, Constant *C, + LVILatticeVal &Result, + const DataLayout &DL, + TargetLibraryInfo *TLI) { + // If we know the value is a constant, evaluate the conditional. - Constant *Res = 0; + Constant *Res = nullptr; if (Result.isConstant()) { - Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD); - if (ConstantInt *ResCI = dyn_cast_or_null(Res)) - return ResCI->isZero() ? False : True; - return Unknown; + Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL, + TLI); + if (ConstantInt *ResCI = dyn_cast(Res)) + return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True; + return LazyValueInfo::Unknown; } - + if (Result.isConstantRange()) { ConstantInt *CI = dyn_cast(C); - if (!CI) return Unknown; - + if (!CI) return LazyValueInfo::Unknown; + ConstantRange CR = Result.getConstantRange(); if (Pred == ICmpInst::ICMP_EQ) { if (!CR.contains(CI->getValue())) - return False; - + return LazyValueInfo::False; + if (CR.isSingleElement() && CR.contains(CI->getValue())) - return True; + return LazyValueInfo::True; } else if (Pred == ICmpInst::ICMP_NE) { if (!CR.contains(CI->getValue())) - return True; - + return LazyValueInfo::True; + if (CR.isSingleElement() && CR.contains(CI->getValue())) - return False; + return LazyValueInfo::False; } - + // Handle more complex predicates. - ConstantRange RHS(CI->getValue(), CI->getValue()+1); - ConstantRange TrueValues = ConstantRange::makeICmpRegion(Pred, RHS); - if (CR.intersectWith(TrueValues).isEmptySet()) - return False; - else if (TrueValues.contains(CR)) - return True; - - return Unknown; + ConstantRange TrueValues = + ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue()); + if (TrueValues.contains(CR)) + return LazyValueInfo::True; + if (TrueValues.inverse().contains(CR)) + return LazyValueInfo::False; + return LazyValueInfo::Unknown; } - + if (Result.isNotConstant()) { // If this is an equality comparison, we can try to fold it knowing that // "V != C1". if (Pred == ICmpInst::ICMP_EQ) { // !C1 == C -> false iff C1 == C. Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE, - Result.getNotConstant(), C, TD); + Result.getNotConstant(), C, DL, + TLI); if (Res->isNullValue()) - return False; + return LazyValueInfo::False; } else if (Pred == ICmpInst::ICMP_NE) { // !C1 != C -> true iff C1 == C. Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE, - Result.getNotConstant(), C, TD); + Result.getNotConstant(), C, DL, + TLI); if (Res->isNullValue()) - return True; + return LazyValueInfo::True; + } + return LazyValueInfo::Unknown; + } + + return LazyValueInfo::Unknown; +} + +/// Determine whether the specified value comparison with a constant is known to +/// be true or false on the specified CFG edge. Pred is a CmpInst predicate. +LazyValueInfo::Tristate +LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C, + BasicBlock *FromBB, BasicBlock *ToBB, + Instruction *CxtI) { + const DataLayout &DL = FromBB->getModule()->getDataLayout(); + LVILatticeVal Result = + getCache(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI); + + return getPredicateResult(Pred, C, Result, DL, TLI); +} + +LazyValueInfo::Tristate +LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C, + Instruction *CxtI) { + const DataLayout &DL = CxtI->getModule()->getDataLayout(); + LVILatticeVal Result = getCache(PImpl, AC, &DL, DT).getValueAt(V, CxtI); + Tristate Ret = getPredicateResult(Pred, C, Result, DL, TLI); + if (Ret != Unknown) + return Ret; + + // Note: The following bit of code is somewhat distinct from the rest of LVI; + // LVI as a whole tries to compute a lattice value which is conservatively + // correct at a given location. In this case, we have a predicate which we + // weren't able to prove about the merged result, and we're pushing that + // predicate back along each incoming edge to see if we can prove it + // separately for each input. As a motivating example, consider: + // bb1: + // %v1 = ... ; constantrange<1, 5> + // br label %merge + // bb2: + // %v2 = ... ; constantrange<10, 20> + // br label %merge + // merge: + // %phi = phi [%v1, %v2] ; constantrange<1,20> + // %pred = icmp eq i32 %phi, 8 + // We can't tell from the lattice value for '%phi' that '%pred' is false + // along each path, but by checking the predicate over each input separately, + // we can. + // We limit the search to one step backwards from the current BB and value. + // We could consider extending this to search further backwards through the + // CFG and/or value graph, but there are non-obvious compile time vs quality + // tradeoffs. + if (CxtI) { + BasicBlock *BB = CxtI->getParent(); + + // Function entry or an unreachable block. Bail to avoid confusing + // analysis below. + pred_iterator PI = pred_begin(BB), PE = pred_end(BB); + if (PI == PE) + return Unknown; + + // If V is a PHI node in the same block as the context, we need to ask + // questions about the predicate as applied to the incoming value along + // each edge. This is useful for eliminating cases where the predicate is + // known along all incoming edges. + if (auto *PHI = dyn_cast(V)) + if (PHI->getParent() == BB) { + Tristate Baseline = Unknown; + for (unsigned i = 0, e = PHI->getNumIncomingValues(); i < e; i++) { + Value *Incoming = PHI->getIncomingValue(i); + BasicBlock *PredBB = PHI->getIncomingBlock(i); + // Note that PredBB may be BB itself. + Tristate Result = getPredicateOnEdge(Pred, Incoming, C, PredBB, BB, + CxtI); + + // Keep going as long as we've seen a consistent known result for + // all inputs. + Baseline = (i == 0) ? Result /* First iteration */ + : (Baseline == Result ? Baseline : Unknown); /* All others */ + if (Baseline == Unknown) + break; + } + if (Baseline != Unknown) + return Baseline; + } + + // For a comparison where the V is outside this block, it's possible + // that we've branched on it before. Look to see if the value is known + // on all incoming edges. + if (!isa(V) || + cast(V)->getParent() != BB) { + // For predecessor edge, determine if the comparison is true or false + // on that edge. If they're all true or all false, we can conclude + // the value of the comparison in this block. + Tristate Baseline = getPredicateOnEdge(Pred, V, C, *PI, BB, CxtI); + if (Baseline != Unknown) { + // Check that all remaining incoming values match the first one. + while (++PI != PE) { + Tristate Ret = getPredicateOnEdge(Pred, V, C, *PI, BB, CxtI); + if (Ret != Baseline) break; + } + // If we terminated early, then one of the values didn't match. + if (PI == PE) { + return Baseline; + } + } } - return Unknown; } - return Unknown; } void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, - BasicBlock* NewSucc) { - if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc); + BasicBlock *NewSucc) { + if (PImpl) { + const DataLayout &DL = PredBB->getModule()->getDataLayout(); + getCache(PImpl, AC, &DL, DT).threadEdge(PredBB, OldSucc, NewSucc); + } } void LazyValueInfo::eraseBlock(BasicBlock *BB) { - if (PImpl) getCache(PImpl).eraseBlock(BB); + if (PImpl) { + const DataLayout &DL = BB->getModule()->getDataLayout(); + getCache(PImpl, AC, &DL, DT).eraseBlock(BB); + } }