checkpoint of the new PHITransAddr code, still not done and not used by

anything.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90779 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 257 insertions, 29 deletions

diff --git a/lib/Analysis/PHITransAddr.cpp b/lib/Analysis/PHITransAddr.cpp
index ce7eca5d27..bdaaac1eaa 100644
--- a/lib/Analysis/PHITransAddr.cpp
+++ b/lib/Analysis/PHITransAddr.cpp
@@ -13,36 +13,178 @@
 
 #include "llvm/Analysis/PHITransAddr.h"
 #include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 using namespace llvm;
 
-/// IsPHITranslatable - If this needs PHI translation, return true if we have
-/// some hope of doing it.  This should be used as a filter to avoid calling
-/// GetPHITranslatedValue in hopeless situations.
-bool PHITransAddr::IsPHITranslatable() const {
-  return true; // not a good filter.
+/// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
+/// if we have some hope of doing it.  This should be used as a filter to
+/// avoid calling PHITranslateValue in hopeless situations.
+bool PHITransAddr::IsPotentiallyPHITranslatable() const {
+  // If the input value is not an instruction, or if it is not defined in CurBB,
+  // then we don't need to phi translate it.
+  Instruction *Inst = dyn_cast<Instruction>(Addr);
+  if (isa<PHINode>(Inst) ||
+      isa<BitCastInst>(Inst) ||
+      isa<GetElementPtrInst>(Inst) ||
+      (Inst->getOpcode() == Instruction::And &&
+       isa<ConstantInt>(Inst->getOperand(1))))
+    return true;
+
+  //   cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
+  //   if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
+  //     cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
+
+  return false;
 }
 
-/// GetPHITranslatedValue - Given a computation that satisfied the
-/// isPHITranslatable predicate, see if we can translate the computation into
-/// the specified predecessor block.  If so, return that value, otherwise
-/// return null.
-Value *PHITransAddr::GetPHITranslatedValue(Value *InVal, BasicBlock *CurBB,
-                                           BasicBlock *Pred,
-                                           const TargetData *TD) const {
-  // Not a great implementation.
-  return 0;
+
+Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
+                                         BasicBlock *PredBB) {
+  // If this is a non-instruction value, it can't require PHI translation.
+  Instruction *Inst = dyn_cast<Instruction>(V);
+  if (Inst == 0) return V;
+  
+  // Determine whether 'Inst' is an input to our PHI translatable expression.
+  bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst);
+  
+  // If 'Inst' is not defined in this block, it is either an input, or an
+  // intermediate result.
+  if (Inst->getParent() != CurBB) {
+    // If it is an input, then it remains an input.
+    if (isInput)
+      return Inst;
+  
+    // Otherwise, it must be an intermediate result.  See if its operands need
+    // to be phi translated, and if so, reconstruct it.
+    
+    if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
+      Value *PHIIn = PHITranslateSubExpr(BC->getOperand(0), CurBB, PredBB);
+      if (PHIIn == 0) return 0;
+      if (PHIIn == BC->getOperand(0))
+        return BC;
+      
+      // Find an available version of this cast.
+      
+      // Constants are trivial to find.
+      if (Constant *C = dyn_cast<Constant>(PHIIn))
+        return ConstantExpr::getBitCast(C, BC->getType());
+      
+      // Otherwise we have to see if a bitcasted version of the incoming pointer
+      // is available.  If so, we can use it, otherwise we have to fail.
+      for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end();
+           UI != E; ++UI) {
+        if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI))
+          if (BCI->getType() == BC->getType())
+            return BCI;
+      }
+      return 0;
+    }
+    
+    // Handle getelementptr with at least one PHI translatable operand.
+    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
+      SmallVector<Value*, 8> GEPOps;
+      BasicBlock *CurBB = GEP->getParent();
+      bool AnyChanged = false;
+      for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
+        Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB);
+        if (GEPOp == 0) return 0;
+        
+        AnyChanged = GEPOp != GEP->getOperand(i);
+        GEPOps.push_back(GEPOp);
+      }
+      
+      if (!AnyChanged)
+        return GEP;
+      
+      // Simplify the GEP to handle 'gep x, 0' -> x etc.
+      if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD))
+        return V;
+      
+      // Scan to see if we have this GEP available.
+      Value *APHIOp = GEPOps[0];
+      for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
+           UI != E; ++UI) {
+        if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
+          if (GEPI->getType() == GEP->getType() &&
+              GEPI->getNumOperands() == GEPOps.size() &&
+              GEPI->getParent()->getParent() == CurBB->getParent()) {
+            bool Mismatch = false;
+            for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
+              if (GEPI->getOperand(i) != GEPOps[i]) {
+                Mismatch = true;
+                break;
+              }
+            if (!Mismatch)
+              return GEPI;
+          }
+      }
+      return 0;
+    }
+    
+    // Handle add with a constant RHS.
+    if (Inst->getOpcode() == Instruction::Add &&
+        isa<ConstantInt>(Inst->getOperand(1))) {
+      // PHI translate the LHS.
+      Constant *RHS = cast<ConstantInt>(Inst->getOperand(1));
+      bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap();
+      bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap();
+      
+      Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB);
+      if (LHS == 0) return 0;
+      
+      // If the PHI translated LHS is an add of a constant, fold the immediates.
+      if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS))
+        if (BOp->getOpcode() == Instruction::Add)
+          if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
+            LHS = BOp->getOperand(0);
+            RHS = ConstantExpr::getAdd(RHS, CI);
+            isNSW = isNUW = false;
+          }
+      
+      // See if the add simplifies away.
+      if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD))
+        return Res;
+      
+      // Otherwise, see if we have this add available somewhere.
+      for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end();
+           UI != E; ++UI) {
+        if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI))
+          if (BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
+              BO->getParent()->getParent() == CurBB->getParent())
+            return BO;
+      }
+      
+      return 0;
+    }
+    
+    // Otherwise, we failed.
+    return 0;
+  }
+
+  // Otherwise, it is defined in this block.  It must be an input and must be
+  // phi translated.
+  assert(isInput && "Instruction defined in block must be an input");
+  
+  
+  abort(); // unimplemented so far.
 }
 
-/// GetAvailablePHITranslatePointer - Return the value computed by
-/// PHITranslatePointer if it dominates PredBB, otherwise return null.
+
+/// PHITranslateValue - PHI translate the current address up the CFG from
+/// CurBB to Pred, updating our state the reflect any needed changes.  This
+/// returns true on failure.
+bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB) {
+  Addr = PHITranslateSubExpr(Addr, CurBB, PredBB);
+  return Addr == 0;
+}
+
+/// GetAvailablePHITranslatedSubExpr - Return the value computed by
+/// PHITranslateSubExpr if it dominates PredBB, otherwise return null.
 Value *PHITransAddr::
-GetAvailablePHITranslatedValue(Value *V,
-                               BasicBlock *CurBB, BasicBlock *PredBB,
-                               const TargetData *TD,
-                               const DominatorTree &DT) const {
+GetAvailablePHITranslatedSubExpr(Value *V, BasicBlock *CurBB,BasicBlock *PredBB,
+                                 const DominatorTree &DT) {
   // See if PHI translation succeeds.
-  V = GetPHITranslatedValue(V, CurBB, PredBB, TD);
-  if (V == 0) return 0;
+  V = PHITranslateSubExpr(V, CurBB, PredBB);
   
   // Make sure the value is live in the predecessor.
   if (Instruction *Inst = dyn_cast_or_null<Instruction>(V))
@@ -51,21 +193,107 @@ GetAvailablePHITranslatedValue(Value *V,
   return V;
 }
 
+
+/// PHITranslateWithInsertion - PHI translate this value into the specified
+/// predecessor block, inserting a computation of the value if it is
+/// unavailable.
+///
+/// All newly created instructions are added to the NewInsts list.  This
+/// returns null on failure.
+///
+Value *PHITransAddr::
+PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
+                          const DominatorTree &DT,
+                          SmallVectorImpl<Instruction*> &NewInsts) {
+  unsigned NISize = NewInsts.size();
+  
+  // Attempt to PHI translate with insertion.
+  Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts);
+  
+  // If successful, return the new value.
+  if (Addr) return Addr;
+  
+  // If not, destroy any intermediate instructions inserted.
+  while (NewInsts.size() != NISize)
+    NewInsts.pop_back_val()->eraseFromParent();
+  return 0;
+}
+
+
 /// InsertPHITranslatedPointer - Insert a computation of the PHI translated
 /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
 /// block.  All newly created instructions are added to the NewInsts list.
 /// This returns null on failure.
 ///
 Value *PHITransAddr::
-InsertPHITranslatedPointer(Value *InVal, BasicBlock *CurBB,
-                           BasicBlock *PredBB, const TargetData *TD,
-                           const DominatorTree &DT,
-                           SmallVectorImpl<Instruction*> &NewInsts) const {
+InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
+                           BasicBlock *PredBB, const DominatorTree &DT,
+                           SmallVectorImpl<Instruction*> &NewInsts) {
   // See if we have a version of this value already available and dominating
-  // PredBB.  If so, there is no need to insert a new copy.
-  if (Value *Res = GetAvailablePHITranslatedValue(InVal, CurBB, PredBB, TD, DT))
+  // PredBB.  If so, there is no need to insert a new instance of it.
+  if (Value *Res = GetAvailablePHITranslatedSubExpr(InVal, CurBB, PredBB, DT))
     return Res;
 
-  // Not a great implementation.
+  // If we don't have an available version of this value, it must be an
+  // instruction.
+  Instruction *Inst = cast<Instruction>(InVal);
+  
+  // Handle bitcast of PHI translatable value.
+  if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
+    Value *OpVal = InsertPHITranslatedSubExpr(BC->getOperand(0),
+                                              CurBB, PredBB, DT, NewInsts);
+    if (OpVal == 0) return 0;
+    
+    // Otherwise insert a bitcast at the end of PredBB.
+    BitCastInst *New = new BitCastInst(OpVal, InVal->getType(),
+                                       InVal->getName()+".phi.trans.insert",
+                                       PredBB->getTerminator());
+    NewInsts.push_back(New);
+    return New;
+  }
+  
+  // Handle getelementptr with at least one PHI operand.
+  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
+    SmallVector<Value*, 8> GEPOps;
+    BasicBlock *CurBB = GEP->getParent();
+    for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
+      Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i),
+                                                CurBB, PredBB, DT, NewInsts);
+      if (OpVal == 0) return 0;
+      GEPOps.push_back(OpVal);
+    }
+    
+    GetElementPtrInst *Result = 
+    GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(),
+                              InVal->getName()+".phi.trans.insert",
+                              PredBB->getTerminator());
+    Result->setIsInBounds(GEP->isInBounds());
+    NewInsts.push_back(Result);
+    return Result;
+  }
+  
+#if 0
+  // FIXME: This code works, but it is unclear that we actually want to insert
+  // a big chain of computation in order to make a value available in a block.
+  // This needs to be evaluated carefully to consider its cost trade offs.
+  
+  // Handle add with a constant RHS.
+  if (Inst->getOpcode() == Instruction::Add &&
+      isa<ConstantInt>(Inst->getOperand(1))) {
+    // PHI translate the LHS.
+    Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0),
+                                              CurBB, PredBB, DT, NewInsts);
+    if (OpVal == 0) return 0;
+    
+    BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1),
+                                           InVal->getName()+".phi.trans.insert",
+                                                    PredBB->getTerminator());
+    Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap());
+    Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap());
+    NewInsts.push_back(Res);
+    return Res;
+  }
+#endif
+  
   return 0;
 }