[pmo] Translate pred mem opt test for ownership and eliminate some unneeded Phis getting inserted by the SSA updater.

We already do the SSA updater optimization if we have an available value in the
same block. If we do not have such an available value, we insert the Phis
despite all of the available values being the same. The small change here just
fixes that issue.

Author: gottesmm

lib/SILOptimizer/Mandatory/PredictableMemOpt.cpp

@@ -583,6 +583,7 @@ AvailableValueAggregator::aggregateFullyAvailableValue(SILType loadTy,
   SILSSAUpdater updater(B.getModule());
   updater.Initialize(loadTy);
 
+  Optional<SILValue> singularValue;
   for (auto *insertPt : insertPts) {
     // Use the scope and location of the store at the insertion point.
     SILBuilderWithScope builder(insertPt, &insertedInsts);
@@ -594,10 +595,21 @@ AvailableValueAggregator::aggregateFullyAvailableValue(SILType loadTy,
       eltVal = builder.emitCopyValueOperation(loc, eltVal);
     }
 
+    if (!singularValue.hasValue()) {
+      singularValue = eltVal;
+    } else if (*singularValue != eltVal) {
+      singularValue = SILValue();
+    }
+
     // And then put the value into the SSA updater.
     updater.AddAvailableValue(insertPt->getParent(), eltVal);
   }
 
+  // If we only are tracking a singular value, we do not need to construct
+  // SSA. Just return that value.
+  if (auto val = singularValue.getValueOr(SILValue()))
+    return val;
+
   // Finally, grab the value from the SSA updater.
   SILValue result = updater.GetValueInMiddleOfBlock(B.getInsertionBB());
   assert(result.getOwnershipKind().isCompatibleWith(ValueOwnershipKind::Owned));
@@ -702,6 +714,7 @@ SILValue AvailableValueAggregator::handlePrimitiveValue(SILType loadTy,
   SILSSAUpdater updater(B.getModule());
   updater.Initialize(loadTy);
 
+  Optional<SILValue> singularValue;
   for (auto *i : insertPts) {
     // Use the scope and location of the store at the insertion point.
     SILBuilderWithScope builder(i, &insertedInsts);
@@ -711,9 +724,20 @@ SILValue AvailableValueAggregator::handlePrimitiveValue(SILType loadTy,
         !builder.hasOwnership() ||
         eltVal.getOwnershipKind().isCompatibleWith(ValueOwnershipKind::Owned));
 
+    if (!singularValue.hasValue()) {
+      singularValue = eltVal;
+    } else if (*singularValue != eltVal) {
+      singularValue = SILValue();
+    }
+
     updater.AddAvailableValue(i->getParent(), eltVal);
   }
 
+  // If we only are tracking a singular value, we do not need to construct
+  // SSA. Just return that value.
+  if (auto val = singularValue.getValueOr(SILValue()))
+    return val;
+
   // Finally, grab the value from the SSA updater.
   SILValue eltVal = updater.GetValueInMiddleOfBlock(B.getInsertionBB());
   assert(!B.hasOwnership() ||