[pmo] Expand an assert that validates that we never handlePrimitiveValues when promoting takes.

The key thing to note here is that when we are processing a take, we validate
that at all destroy points we have a fully available value. So we should never
hit this code path which is correct. This assert just makes the assumption
clearer in the small when reading code locally in handlePrimitiveValue.

Author: gottesmm

lib/SILOptimizer/Mandatory/PredictableMemOpt.cpp

@@ -567,6 +567,10 @@ SILValue AvailableValueAggregator::aggregateValues(SILType LoadTy,
     return aggregateStructSubElts(SD, LoadTy, Address, FirstElt);
 
   // Otherwise, we have a non-aggregate primitive. Load or extract the value.
+  //
+  // NOTE: We should never call this when taking since when taking we know that
+  // our underlying value is always fully available.
+  assert(!isTake());
   return handlePrimitiveValue(LoadTy, Address, FirstElt);
 }
 
@@ -696,17 +700,18 @@ SILValue AvailableValueAggregator::aggregateStructSubElts(StructDecl *sd,
   return B.createStruct(Loc, loadTy, resultElts);
 }
 
-// We have looked through all of the aggregate values and finally found a
-// "primitive value". If the value is available, use it (extracting if we need
-// to), otherwise emit a load of the value with the appropriate qualifier.
+// We have looked through all of the aggregate values and finally found a value
+// that is not available without transforming, i.e. a "primitive value". If the
+// value is available, use it (extracting if we need to), otherwise emit a load
+// of the value with the appropriate qualifier.
 SILValue AvailableValueAggregator::handlePrimitiveValue(SILType loadTy,
                                                         SILValue address,
                                                         unsigned firstElt) {
-  auto &val = AvailableValueList[firstElt];
+  assert(!isTake() && "Should only take fully available values?!");
 
   // If the value is not available, load the value and update our use list.
+  auto &val = AvailableValueList[firstElt];
   if (!val) {
-    assert(!isTake() && "Should only take fully available values?!");
     LoadInst *load = ([&]() {
       if (B.hasOwnership()) {
         return B.createTrivialLoadOr(Loc, address,