Fix an error in BBVectorize important for vectorizing pointer types.

When vectorizing pointer types it is important to realize that potential
pairs cannot be connected via the address pointer argument of a load or store.
This is because even after vectorization, the address is still a scalar because
the address of the higher half of the pair is implicit from the address of the
lower half (it need not be, and should not be, explicitly computed).

llvm-svn: 154735

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
index ba033183758..290d82dc77a 100644
--- a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -858,16 +858,33 @@ namespace {
                       std::vector<Value *> &PairableInsts,
                       std::multimap<ValuePair, ValuePair> &ConnectedPairs,
                       ValuePair P) {
+    StoreInst *SI, *SJ;
+
     // For each possible pairing for this variable, look at the uses of
     // the first value...
     for (Value::use_iterator I = P.first->use_begin(),
          E = P.first->use_end(); I != E; ++I) {
+      if (isa<LoadInst>(*I)) {
+        // A pair cannot be connected to a load because the load only takes one
+        // operand (the address) and it is a scalar even after vectorization.
+        continue;
+      } else if ((SI = dyn_cast<StoreInst>(*I)) &&
+                 P.first == SI->getPointerOperand()) {
+        // Similarly, a pair cannot be connected to a store through its
+        // pointer operand.
+        continue;
+      }
+
       VPIteratorPair IPairRange = CandidatePairs.equal_range(*I);
 
       // For each use of the first variable, look for uses of the second
       // variable...
       for (Value::use_iterator J = P.second->use_begin(),
            E2 = P.second->use_end(); J != E2; ++J) {
+        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+            P.second == SJ->getPointerOperand())
+          continue;
+
         VPIteratorPair JPairRange = CandidatePairs.equal_range(*J);
 
         // Look for <I, J>:
@@ -883,6 +900,10 @@ namespace {
       // Look for cases where just the first value in the pair is used by
       // both members of another pair (splatting).
       for (Value::use_iterator J = P.first->use_begin(); J != E; ++J) {
+        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+            P.first == SJ->getPointerOperand())
+          continue;
+
         if (isSecondInIteratorPair<Value*>(*J, IPairRange))
           ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J)));
       }
@@ -893,9 +914,19 @@ namespace {
     // both members of another pair (splatting).
     for (Value::use_iterator I = P.second->use_begin(),
          E = P.second->use_end(); I != E; ++I) {
+      if (isa<LoadInst>(*I))
+        continue;
+      else if ((SI = dyn_cast<StoreInst>(*I)) &&
+               P.second == SI->getPointerOperand())
+        continue;
+
       VPIteratorPair IPairRange = CandidatePairs.equal_range(*I);
 
       for (Value::use_iterator J = P.second->use_begin(); J != E; ++J) {
+        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+            P.second == SJ->getPointerOperand())
+          continue;
+
         if (isSecondInIteratorPair<Value*>(*J, IPairRange))
           ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J)));
       }