Vendor import of llvm trunk r126079:vendor/llvm/llvm-r126079

http://llvm.org/svn/llvm-project/llvm/trunk@126079

1 files changed, 470 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/EarlyCSE.cpp b/lib/Transforms/Scalar/EarlyCSE.cpp
new file mode 100644
index 000000000000..3d3f17b26fc6
--- /dev/null
+++ b/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -0,0 +1,470 @@
+//===- EarlyCSE.cpp - Simple and fast CSE pass ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs a simple dominator tree walk that eliminates trivially
+// redundant instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "early-cse"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Instructions.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/RecyclingAllocator.h"
+#include "llvm/ADT/ScopedHashTable.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumSimplify, "Number of instructions simplified or DCE'd");
+STATISTIC(NumCSE,      "Number of instructions CSE'd");
+STATISTIC(NumCSELoad,  "Number of load instructions CSE'd");
+STATISTIC(NumCSECall,  "Number of call instructions CSE'd");
+STATISTIC(NumDSE,      "Number of trivial dead stores removed");
+
+static unsigned getHash(const void *V) {
+  return DenseMapInfo<const void*>::getHashValue(V);
+}
+
+//===----------------------------------------------------------------------===//
+// SimpleValue 
+//===----------------------------------------------------------------------===//
+
+namespace {
+  /// SimpleValue - Instances of this struct represent available values in the
+  /// scoped hash table.
+  struct SimpleValue {
+    Instruction *Inst;
+    
+    SimpleValue(Instruction *I) : Inst(I) {
+      assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
+    }
+    
+    bool isSentinel() const {
+      return Inst == DenseMapInfo<Instruction*>::getEmptyKey() ||
+             Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
+    }
+    
+    static bool canHandle(Instruction *Inst) {
+      // This can only handle non-void readnone functions.
+      if (CallInst *CI = dyn_cast<CallInst>(Inst))
+        return CI->doesNotAccessMemory() && !CI->getType()->isVoidTy();
+      return isa<CastInst>(Inst) || isa<BinaryOperator>(Inst) ||
+             isa<GetElementPtrInst>(Inst) || isa<CmpInst>(Inst) ||
+             isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
+             isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst) ||
+             isa<ExtractValueInst>(Inst) || isa<InsertValueInst>(Inst);
+    }
+  };
+}
+
+namespace llvm {
+// SimpleValue is POD.
+template<> struct isPodLike<SimpleValue> {
+  static const bool value = true;
+};
+
+template<> struct DenseMapInfo<SimpleValue> {
+  static inline SimpleValue getEmptyKey() {
+    return DenseMapInfo<Instruction*>::getEmptyKey();
+  }
+  static inline SimpleValue getTombstoneKey() {
+    return DenseMapInfo<Instruction*>::getTombstoneKey();
+  }
+  static unsigned getHashValue(SimpleValue Val);
+  static bool isEqual(SimpleValue LHS, SimpleValue RHS);
+};
+}
+
+unsigned DenseMapInfo<SimpleValue>::getHashValue(SimpleValue Val) {
+  Instruction *Inst = Val.Inst;
+  
+  // Hash in all of the operands as pointers.
+  unsigned Res = 0;
+  for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
+    Res ^= getHash(Inst->getOperand(i)) << i;
+
+  if (CastInst *CI = dyn_cast<CastInst>(Inst))
+    Res ^= getHash(CI->getType());
+  else if (CmpInst *CI = dyn_cast<CmpInst>(Inst))
+    Res ^= CI->getPredicate();
+  else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Inst)) {
+    for (ExtractValueInst::idx_iterator I = EVI->idx_begin(),
+         E = EVI->idx_end(); I != E; ++I)
+      Res ^= *I;
+  } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(Inst)) {
+    for (InsertValueInst::idx_iterator I = IVI->idx_begin(),
+         E = IVI->idx_end(); I != E; ++I)
+      Res ^= *I;
+  } else {
+    // nothing extra to hash in.
+    assert((isa<CallInst>(Inst) ||
+            isa<BinaryOperator>(Inst) || isa<GetElementPtrInst>(Inst) ||
+            isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
+            isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst)) &&
+           "Invalid/unknown instruction");
+  }
+
+  // Mix in the opcode.
+  return (Res << 1) ^ Inst->getOpcode();
+}
+
+bool DenseMapInfo<SimpleValue>::isEqual(SimpleValue LHS, SimpleValue RHS) {
+  Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
+
+  if (LHS.isSentinel() || RHS.isSentinel())
+    return LHSI == RHSI;
+  
+  if (LHSI->getOpcode() != RHSI->getOpcode()) return false;
+  return LHSI->isIdenticalTo(RHSI);
+}
+
+//===----------------------------------------------------------------------===//
+// CallValue 
+//===----------------------------------------------------------------------===//
+
+namespace {
+  /// CallValue - Instances of this struct represent available call values in
+  /// the scoped hash table.
+  struct CallValue {
+    Instruction *Inst;
+    
+    CallValue(Instruction *I) : Inst(I) {
+      assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
+    }
+    
+    bool isSentinel() const {
+      return Inst == DenseMapInfo<Instruction*>::getEmptyKey() ||
+             Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
+    }
+    
+    static bool canHandle(Instruction *Inst) {
+      // Don't value number anything that returns void.
+      if (Inst->getType()->isVoidTy())
+        return false;
+      
+      CallInst *CI = dyn_cast<CallInst>(Inst);
+      if (CI == 0 || !CI->onlyReadsMemory())
+        return false;
+      return true;
+    }
+  };
+}
+
+namespace llvm {
+  // CallValue is POD.
+  template<> struct isPodLike<CallValue> {
+    static const bool value = true;
+  };
+  
+  template<> struct DenseMapInfo<CallValue> {
+    static inline CallValue getEmptyKey() {
+      return DenseMapInfo<Instruction*>::getEmptyKey();
+    }
+    static inline CallValue getTombstoneKey() {
+      return DenseMapInfo<Instruction*>::getTombstoneKey();
+    }
+    static unsigned getHashValue(CallValue Val);
+    static bool isEqual(CallValue LHS, CallValue RHS);
+  };
+}
+unsigned DenseMapInfo<CallValue>::getHashValue(CallValue Val) {
+  Instruction *Inst = Val.Inst;
+  // Hash in all of the operands as pointers.
+  unsigned Res = 0;
+  for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) {
+    assert(!Inst->getOperand(i)->getType()->isMetadataTy() &&
+           "Cannot value number calls with metadata operands");
+    Res ^= getHash(Inst->getOperand(i)) << i;
+  }
+  
+  // Mix in the opcode.
+  return (Res << 1) ^ Inst->getOpcode();
+}
+
+bool DenseMapInfo<CallValue>::isEqual(CallValue LHS, CallValue RHS) {
+  Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
+  if (LHS.isSentinel() || RHS.isSentinel())
+    return LHSI == RHSI;
+  return LHSI->isIdenticalTo(RHSI);
+}
+
+
+//===----------------------------------------------------------------------===//
+// EarlyCSE pass. 
+//===----------------------------------------------------------------------===//
+
+namespace {
+  
+/// EarlyCSE - This pass does a simple depth-first walk over the dominator
+/// tree, eliminating trivially redundant instructions and using instsimplify
+/// to canonicalize things as it goes.  It is intended to be fast and catch
+/// obvious cases so that instcombine and other passes are more effective.  It
+/// is expected that a later pass of GVN will catch the interesting/hard
+/// cases.
+class EarlyCSE : public FunctionPass {
+public:
+  const TargetData *TD;
+  DominatorTree *DT;
+  typedef RecyclingAllocator<BumpPtrAllocator,
+                      ScopedHashTableVal<SimpleValue, Value*> > AllocatorTy;
+  typedef ScopedHashTable<SimpleValue, Value*, DenseMapInfo<SimpleValue>,
+                          AllocatorTy> ScopedHTType;
+  
+  /// AvailableValues - This scoped hash table contains the current values of
+  /// all of our simple scalar expressions.  As we walk down the domtree, we
+  /// look to see if instructions are in this: if so, we replace them with what
+  /// we find, otherwise we insert them so that dominated values can succeed in
+  /// their lookup.
+  ScopedHTType *AvailableValues;
+  
+  /// AvailableLoads - This scoped hash table contains the current values
+  /// of loads.  This allows us to get efficient access to dominating loads when
+  /// we have a fully redundant load.  In addition to the most recent load, we
+  /// keep track of a generation count of the read, which is compared against
+  /// the current generation count.  The current generation count is
+  /// incremented after every possibly writing memory operation, which ensures
+  /// that we only CSE loads with other loads that have no intervening store.
+  typedef RecyclingAllocator<BumpPtrAllocator,
+    ScopedHashTableVal<Value*, std::pair<Value*, unsigned> > > LoadMapAllocator;
+  typedef ScopedHashTable<Value*, std::pair<Value*, unsigned>,
+                          DenseMapInfo<Value*>, LoadMapAllocator> LoadHTType;
+  LoadHTType *AvailableLoads;
+  
+  /// AvailableCalls - This scoped hash table contains the current values
+  /// of read-only call values.  It uses the same generation count as loads.
+  typedef ScopedHashTable<CallValue, std::pair<Value*, unsigned> > CallHTType;
+  CallHTType *AvailableCalls;
+  
+  /// CurrentGeneration - This is the current generation of the memory value.
+  unsigned CurrentGeneration;
+  
+  static char ID;
+  explicit EarlyCSE() : FunctionPass(ID) {
+    initializeEarlyCSEPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F);
+
+private:
+  
+  bool processNode(DomTreeNode *Node);
+  
+  // This transformation requires dominator postdominator info
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.addRequired<DominatorTree>();
+    AU.setPreservesCFG();
+  }
+};
+}
+
+char EarlyCSE::ID = 0;
+
+// createEarlyCSEPass - The public interface to this file.
+FunctionPass *llvm::createEarlyCSEPass() {
+  return new EarlyCSE();
+}
+
+INITIALIZE_PASS_BEGIN(EarlyCSE, "early-cse", "Early CSE", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_END(EarlyCSE, "early-cse", "Early CSE", false, false)
+
+bool EarlyCSE::processNode(DomTreeNode *Node) {
+  // Define a scope in the scoped hash table.  When we are done processing this
+  // domtree node and recurse back up to our parent domtree node, this will pop
+  // off all the values we install.
+  ScopedHTType::ScopeTy Scope(*AvailableValues);
+  
+  // Define a scope for the load values so that anything we add will get
+  // popped when we recurse back up to our parent domtree node.
+  LoadHTType::ScopeTy LoadScope(*AvailableLoads);
+  
+  // Define a scope for the call values so that anything we add will get
+  // popped when we recurse back up to our parent domtree node.
+  CallHTType::ScopeTy CallScope(*AvailableCalls);
+  
+  BasicBlock *BB = Node->getBlock();
+  
+  // If this block has a single predecessor, then the predecessor is the parent
+  // of the domtree node and all of the live out memory values are still current
+  // in this block.  If this block has multiple predecessors, then they could
+  // have invalidated the live-out memory values of our parent value.  For now,
+  // just be conservative and invalidate memory if this block has multiple
+  // predecessors.
+  if (BB->getSinglePredecessor() == 0)
+    ++CurrentGeneration;
+  
+  /// LastStore - Keep track of the last non-volatile store that we saw... for
+  /// as long as there in no instruction that reads memory.  If we see a store
+  /// to the same location, we delete the dead store.  This zaps trivial dead
+  /// stores which can occur in bitfield code among other things.
+  StoreInst *LastStore = 0;
+  
+  bool Changed = false;
+
+  // See if any instructions in the block can be eliminated.  If so, do it.  If
+  // not, add them to AvailableValues.
+  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
+    Instruction *Inst = I++;
+    
+    // Dead instructions should just be removed.
+    if (isInstructionTriviallyDead(Inst)) {
+      DEBUG(dbgs() << "EarlyCSE DCE: " << *Inst << '\n');
+      Inst->eraseFromParent();
+      Changed = true;
+      ++NumSimplify;
+      continue;
+    }
+    
+    // If the instruction can be simplified (e.g. X+0 = X) then replace it with
+    // its simpler value.
+    if (Value *V = SimplifyInstruction(Inst, TD, DT)) {
+      DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << "  to: " << *V << '\n');
+      Inst->replaceAllUsesWith(V);
+      Inst->eraseFromParent();
+      Changed = true;
+      ++NumSimplify;
+      continue;
+    }
+    
+    // If this is a simple instruction that we can value number, process it.
+    if (SimpleValue::canHandle(Inst)) {
+      // See if the instruction has an available value.  If so, use it.
+      if (Value *V = AvailableValues->lookup(Inst)) {
+        DEBUG(dbgs() << "EarlyCSE CSE: " << *Inst << "  to: " << *V << '\n');
+        Inst->replaceAllUsesWith(V);
+        Inst->eraseFromParent();
+        Changed = true;
+        ++NumCSE;
+        continue;
+      }
+      
+      // Otherwise, just remember that this value is available.
+      AvailableValues->insert(Inst, Inst);
+      continue;
+    }
+    
+    // If this is a non-volatile load, process it.
+    if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+      // Ignore volatile loads.
+      if (LI->isVolatile()) {
+        LastStore = 0;
+        continue;
+      }
+      
+      // If we have an available version of this load, and if it is the right
+      // generation, replace this instruction.
+      std::pair<Value*, unsigned> InVal =
+        AvailableLoads->lookup(Inst->getOperand(0));
+      if (InVal.first != 0 && InVal.second == CurrentGeneration) {
+        DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst << "  to: "
+              << *InVal.first << '\n');
+        if (!Inst->use_empty()) Inst->replaceAllUsesWith(InVal.first);
+        Inst->eraseFromParent();
+        Changed = true;
+        ++NumCSELoad;
+        continue;
+      }
+      
+      // Otherwise, remember that we have this instruction.
+      AvailableLoads->insert(Inst->getOperand(0),
+                          std::pair<Value*, unsigned>(Inst, CurrentGeneration));
+      LastStore = 0;
+      continue;
+    }
+    
+    // If this instruction may read from memory, forget LastStore.
+    if (Inst->mayReadFromMemory())
+      LastStore = 0;
+    
+    // If this is a read-only call, process it.
+    if (CallValue::canHandle(Inst)) {
+      // If we have an available version of this call, and if it is the right
+      // generation, replace this instruction.
+      std::pair<Value*, unsigned> InVal = AvailableCalls->lookup(Inst);
+      if (InVal.first != 0 && InVal.second == CurrentGeneration) {
+        DEBUG(dbgs() << "EarlyCSE CSE CALL: " << *Inst << "  to: "
+                     << *InVal.first << '\n');
+        if (!Inst->use_empty()) Inst->replaceAllUsesWith(InVal.first);
+        Inst->eraseFromParent();
+        Changed = true;
+        ++NumCSECall;
+        continue;
+      }
+      
+      // Otherwise, remember that we have this instruction.
+      AvailableCalls->insert(Inst,
+                         std::pair<Value*, unsigned>(Inst, CurrentGeneration));
+      continue;
+    }
+    
+    // Okay, this isn't something we can CSE at all.  Check to see if it is
+    // something that could modify memory.  If so, our available memory values
+    // cannot be used so bump the generation count.
+    if (Inst->mayWriteToMemory()) {
+      ++CurrentGeneration;
+     
+      if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+        // We do a trivial form of DSE if there are two stores to the same
+        // location with no intervening loads.  Delete the earlier store.
+        if (LastStore &&
+            LastStore->getPointerOperand() == SI->getPointerOperand()) {
+          DEBUG(dbgs() << "EarlyCSE DEAD STORE: " << *LastStore << "  due to: "
+                       << *Inst << '\n');
+          LastStore->eraseFromParent();
+          Changed = true;
+          ++NumDSE;
+          LastStore = 0;
+          continue;
+        }
+        
+        // Okay, we just invalidated anything we knew about loaded values.  Try
+        // to salvage *something* by remembering that the stored value is a live
+        // version of the pointer.  It is safe to forward from volatile stores
+        // to non-volatile loads, so we don't have to check for volatility of
+        // the store.
+        AvailableLoads->insert(SI->getPointerOperand(),
+         std::pair<Value*, unsigned>(SI->getValueOperand(), CurrentGeneration));
+        
+        // Remember that this was the last store we saw for DSE.
+        if (!SI->isVolatile())
+          LastStore = SI;
+      }
+    }
+  }
+  
+  unsigned LiveOutGeneration = CurrentGeneration;
+  for (DomTreeNode::iterator I = Node->begin(), E = Node->end(); I != E; ++I) {
+    Changed |= processNode(*I);
+    // Pop any generation changes off the stack from the recursive walk.
+    CurrentGeneration = LiveOutGeneration;
+  }
+  return Changed;
+}
+
+
+bool EarlyCSE::runOnFunction(Function &F) {
+  TD = getAnalysisIfAvailable<TargetData>();
+  DT = &getAnalysis<DominatorTree>();
+  
+  // Tables that the pass uses when walking the domtree.
+  ScopedHTType AVTable;
+  AvailableValues = &AVTable;
+  LoadHTType LoadTable;
+  AvailableLoads = &LoadTable;
+  CallHTType CallTable;
+  AvailableCalls = &CallTable;
+  
+  CurrentGeneration = 0;
+  return processNode(DT->getRootNode());
+}