[NFC] Add a method to just ask if a tuple AP vanishes under substitution

Author: rjmccall

include/swift/SIL/AbstractionPattern.h

@@ -1344,6 +1344,10 @@ class AbstractionPattern {
   /// returned element is the pattern type of the expansion.
   Optional<AbstractionPattern> getVanishingTupleElementPatternType() const;
 
+  /// Does this tuple type vanish, i.e. is it flattened to a singleton
+  /// non-expansion element under substitution?
+  bool doesTupleVanish() const;
+
   static AbstractionPattern
   projectTupleElementType(const AbstractionPattern *base, size_t index) {
     return base->getTupleElementType(index);

include/swift/SIL/AbstractionPatternGenerators.h

@@ -224,6 +224,11 @@ class TupleElementGenerator {
     return origEltIndex == numOrigElts;
   }
 
+  /// Does the entire original tuple vanish?
+  bool doesOrigTupleVanish() const {
+    return origTupleVanishes;
+  }
+
   /// Advance to the next orig element.
   void advance() {
     assert(!isFinished());

lib/SIL/IR/AbstractionPattern.cpp

@@ -314,7 +314,7 @@ bool AbstractionPattern::matchesTuple(CanType substType) const {
       return false;
     LLVM_FALLTHROUGH;
   case Kind::Tuple: {
-    if (getVanishingTupleElementPatternType()) {
+    if (doesTupleVanish()) {
       // TODO: recurse into elements.
       return true;
     }
@@ -480,6 +480,11 @@ bool AbstractionPattern::doesTupleContainPackExpansionType() const {
   llvm_unreachable("bad kind");
 }
 
+bool AbstractionPattern::doesTupleVanish() const {
+  assert(isTuple());
+  return getVanishingTupleElementPatternType().hasValue();
+}
+
 Optional<AbstractionPattern>
 AbstractionPattern::getVanishingTupleElementPatternType() const {
   if (!isTuple()) return None;
@@ -552,8 +557,7 @@ TupleElementGenerator::TupleElementGenerator(
   assert(origTupleType.isTuple());
   assert(origTupleType.matchesTuple(substType));
 
-  origTupleVanishes =
-    origTupleType.getVanishingTupleElementPatternType().hasValue();
+  origTupleVanishes = origTupleType.doesTupleVanish();
   origTupleTypeIsOpaque = origTupleType.isOpaqueTuple();
   numOrigElts = origTupleType.getNumTupleElements();
 

lib/SILGen/ResultPlan.cpp

@@ -1326,7 +1326,7 @@ ResultPlanPtr ResultPlanBuilder::buildForTuple(Initialization *init,
   // emit directly into the initialization.  If the orig tuple vanishes,
   // that counts as the initialization being splittable.
   if (init) {
-    bool vanishes = origType.getVanishingTupleElementPatternType().hasValue();
+    bool vanishes = origType.doesTupleVanish();
     if (vanishes || init->canSplitIntoTupleElements()) {
       return ResultPlanPtr(
         new TupleInitializationResultPlan(*this, init, origType, substType,

lib/SILGen/SILGenApply.cpp

@@ -3416,8 +3416,7 @@ class ArgEmitter {
     // If the original parameter type is a vanishing tuple, we want to emit
     // this as if the argument source was wrapped in an extra level of
     // tuple literal.
-    bool origTupleVanishes =
-      origParamType.getVanishingTupleElementPatternType().hasValue();
+    bool origTupleVanishes = origParamType.doesTupleVanish();
 
     auto substType = arg.getSubstRValueType();
 

lib/SILGen/SILGenStmt.cpp

@@ -588,8 +588,7 @@ prepareIndirectResultInit(SILGenFunction &SGF, SILLocation loc,
     TupleInitialization *tupleInit = nullptr;
     SmallVector<InitializationPtr, 1> singletonEltInit;
 
-    bool vanishes =
-      origResultType.getVanishingTupleElementPatternType().hasValue();
+    bool vanishes = origResultType.doesTupleVanish();
     if (!vanishes) {
       auto resultTupleType = cast<TupleType>(resultType);
       tupleInit = new TupleInitialization(resultTupleType);