[SIL] SubstitutionList -> SubstitutionMap in devirtualizer.

Author: DougGregor

lib/SILOptimizer/Utils/Devirtualize.cpp

@@ -765,7 +765,7 @@ swift::tryDevirtualizeClassMethod(FullApplySite AI, SILValue ClassInstance,
 /// \param conformanceRef The (possibly-specialized) conformance
 /// \param requirementSig The generic signature of the requirement
 /// \param witnessThunkSig The generic signature of the witness method
-/// \param origSubs The substitutions from the call instruction
+/// \param origSubMap The substitutions from the call instruction
 /// \param isDefaultWitness True if this is a default witness method
 /// \param classWitness The ClassDecl if this is a class witness method
 static SubstitutionMap
@@ -774,15 +774,13 @@ getWitnessMethodSubstitutions(
     ProtocolConformanceRef conformanceRef,
     GenericSignature *requirementSig,
     GenericSignature *witnessThunkSig,
-    SubstitutionList origSubs,
+    SubstitutionMap origSubMap,
     bool isDefaultWitness,
     ClassDecl *classWitness) {
 
   if (witnessThunkSig == nullptr)
     return SubstitutionMap();
 
-  auto origSubMap = requirementSig->getSubstitutionMap(origSubs);
-
   if (isDefaultWitness)
     return origSubMap;
 
@@ -841,7 +839,7 @@ getWitnessMethodSubstitutions(SILModule &Module, ApplySite AI, SILFunction *F,
   auto requirementSig = AI.getOrigCalleeType()->getGenericSignature();
   auto witnessThunkSig = witnessFnTy->getGenericSignature();
 
-  SubstitutionList origSubs = AI.getSubstitutions();
+  SubstitutionMap origSubs = AI.getSubstitutionMap();
 
   auto *mod = Module.getSwiftModule();
   bool isDefaultWitness =