Implement partial specialization behind a flag.

Partial specialization is disabled by default. Use -sil-partial-specialization to enable it.

Use -sil-partial-specialization-with-generic-substitutions to enable the partial specialization even in cases of substitutions containing generic replacement types.

Author: swiftix

include/swift/SILOptimizer/Utils/Generics.h

@@ -115,6 +115,15 @@ class ReabstractionInfo {
                                            bool HasUnboundGenericParams);
 
   void createSubstitutedAndSpecializedTypes();
+  bool prepareAndCheck(ApplySite Apply, SILFunction *Callee,
+                       SubstitutionList ParamSubs);
+  void specializeConcreteAndGenericSubstitutions(ApplySite Apply,
+                                                 SILFunction *Callee,
+                                                 SubstitutionList ParamSubs);
+  void specializeConcreteSubstitutions(ApplySite Apply, SILFunction *Callee,
+                                       SubstitutionList ParamSubs);
+
+  ReabstractionInfo() {}
 public:
   /// Constructs the ReabstractionInfo for generic function \p Orig with
   /// substitutions \p ParamSubs.
@@ -219,6 +228,10 @@ class ReabstractionInfo {
 
   /// Returns true if it is a partial generic specialization.
   bool isPartialSpecialization() const;
+
+  /// Returns true if a given apply can be specialized.
+  static bool canBeSpecialized(ApplySite Apply, SILFunction *Callee,
+                               SubstitutionList ParamSubs);
 };
 
 /// Helper class for specializing a generic function given a list of

lib/SILOptimizer/Transforms/PerformanceInliner.cpp

@@ -316,8 +316,7 @@ SILFunction *SILPerformanceInliner::getEligibleFunction(FullApplySite AI) {
 // specialization for a given call.
 static bool canSpecializeGeneric(ApplySite AI, SILFunction *F,
                                  SubstitutionList Subs) {
-  ReabstractionInfo ReInfo(AI, F, Subs);
-  return ReInfo.canBeSpecialized();
+  return ReabstractionInfo::canBeSpecialized(AI, F, Subs);
 }
 
 bool SILPerformanceInliner::isProfitableToInline(FullApplySite AI,