Fix phi translation in load PRE to agree with the phi

translation done by memdep, and reenable gep translation 
again.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89992 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -244,6 +244,13 @@ namespace llvm {
                                       BasicBlock *BB,
                                      SmallVectorImpl<NonLocalDepEntry> &Result);
     
+    /// PHITranslatePointer - Find an available version of the specified value
+    /// PHI translated across the specified edge.  If MemDep isn't able to
+    /// satisfy this request, it returns null.
+    Value *PHITranslatePointer(Value *V,
+                               BasicBlock *CurBB, BasicBlock *PredBB,
+                               const TargetData *TD) const;
+    
     /// removeInstruction - Remove an instruction from the dependence analysis,
     /// updating the dependence of instructions that previously depended on it.
     void removeInstruction(Instruction *InstToRemove);

lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -700,7 +700,6 @@ static bool isPHITranslatable(Instruction *Inst) {
   
   // We can translate a GEP that uses a PHI in the current block for at least
   // one of its operands.
-  if (0)
   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
     for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i)
       if (PHINode *PN = dyn_cast<PHINode>(GEP->getOperand(i)))
@@ -718,8 +717,15 @@ static bool isPHITranslatable(Instruction *Inst) {
 /// PHITranslateForPred - 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.
-static Value *PHITranslateForPred(Instruction *Inst, BasicBlock *Pred,
-                                  const TargetData *TD) {
+Value *MemoryDependenceAnalysis::
+PHITranslatePointer(Value *InVal, BasicBlock *CurBB, BasicBlock *Pred,
+                    const TargetData *TD) 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>(InVal);
+  if (Inst == 0 || Inst->getParent() != CurBB)
+    return InVal;
+  
   if (PHINode *PN = dyn_cast<PHINode>(Inst))
     return PN->getIncomingValueForBlock(Pred);
   
@@ -931,7 +937,7 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
       
       for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
         BasicBlock *Pred = *PI;
-        Value *PredPtr = PHITranslateForPred(PtrInst, Pred, TD);
+        Value *PredPtr = PHITranslatePointer(PtrInst, BB, Pred, TD);
         
         // If PHI translation fails, bail out.
         if (PredPtr == 0)

lib/Transforms/Scalar/GVN.cpp

@@ -1427,13 +1427,19 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
 
   // If the loaded pointer is PHI node defined in this block, do PHI translation
   // to get its value in the predecessor.
-  Value *LoadPtr = LI->getOperand(0)->DoPHITranslation(LoadBB, UnavailablePred);
+  Value *LoadPtr = MD->PHITranslatePointer(LI->getOperand(0),
+                                           LoadBB, UnavailablePred, TD);
+  if (LoadPtr == 0) {
+    DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR CAN'T BE PHI TRANSLATED: "
+          << *LI->getOperand(0) << '\n' << *LI << "\n");
+    return false;
+  }
 
   // Make sure the value is live in the predecessor.  If it was defined by a
   // non-PHI instruction in this block, we don't know how to recompute it above.
   if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr))
     if (!DT->dominates(LPInst->getParent(), UnavailablePred)) {
-      DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR IS UNAVAILABLE IN PRED: "
+      DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR DOES NOT DOMINATE PRED: "
                    << *LPInst << '\n' << *LI << "\n");
       return false;
     }

test/Transforms/GVN/rle-phi-translate.ll

@@ -80,9 +80,9 @@ bb2:
 	%i = phi i32 [ 7, %bb1 ], [ 17, %bb ]
   %d1 = getelementptr i32* %d, i32 %i
 	%dv = load i32* %d1
-; HECK: %dv = phi i32 [ 82, %bb1 ], [ 4, %bb ]
-; HECK-NOT: load
-; HECK: ret i32 %dv
+; CHECK: %dv = phi i32 [ 82, %bb1 ], [ 4, %bb ]
+; CHECK-NOT: load
+; CHECK: ret i32 %dv
 	ret i32 %dv
 }
 
@@ -106,9 +106,9 @@ bb2:
 	%i = phi i32 [ 7, %bb1 ], [ 0, %bb ]
   %d1 = getelementptr i32* %d, i32 %i
 	%dv = load i32* %d1
-; HECK: %dv = phi i32 [ 82, %bb1 ], [ 4, %bb ]
-; HECK-NOT: load
-; HECK: ret i32 %dv
+; CHECK: %dv = phi i32 [ 82, %bb1 ], [ 4, %bb ]
+; CHECK-NOT: load
+; CHECK: ret i32 %dv
 	ret i32 %dv
 }