[SILOptimizer] Add prespecialization for arbitray reference types (#58846)

* [SILOptimizer] Add prespecialization for arbitray reference types

* Fix benchmark Package.swift

* Move SimpleArray to utils

* Fix multiple indirect result case

* Remove leftover code from previous attempt

* Fix test after rebase

* Move code to compute type replacements to SpecializedFunction

* Fix ownership when OSSA is enabled

* Fixes after rebase

* Changes after rebasing

* Add feature flag for layout pre-specialization

* Fix pre_specialize-macos.swift

* Add compiler flag to benchmark build

* Fix benchmark SwiftPM flags

include/swift/SIL/SILFunction.h

@@ -82,6 +82,7 @@ public:
 
   static SILSpecializeAttr *create(SILModule &M,
                                    GenericSignature specializedSignature,
+                                   ArrayRef<Type> typeErasedParams,
                                    bool exported, SpecializationKind kind,
                                    SILFunction *target, Identifier spiGroup,
                                    const ModuleDecl *spiModule,
@@ -107,6 +108,14 @@ public:
     return specializedSignature;
   }
 
+  GenericSignature getUnerasedSpecializedSignature() const {
+    return unerasedSpecializedSignature;
+  }
+
+  ArrayRef<Type> getTypeErasedParams() const {
+    return typeErasedParams;
+  }
+
   SILFunction *getFunction() const {
     return F;
   }
@@ -133,6 +142,8 @@ private:
   SpecializationKind kind;
   bool exported;
   GenericSignature specializedSignature;
+  GenericSignature unerasedSpecializedSignature;
+  llvm::SmallVector<Type, 2> typeErasedParams;
   Identifier spiGroup;
   AvailabilityContext availability;
   const ModuleDecl *spiModule = nullptr;
@@ -140,8 +151,11 @@ private:
   SILFunction *targetFunction = nullptr;
 
   SILSpecializeAttr(bool exported, SpecializationKind kind,
-                    GenericSignature specializedSignature, SILFunction *target,
-                    Identifier spiGroup, const ModuleDecl *spiModule,
+                    GenericSignature specializedSignature,
+                    GenericSignature unerasedSpecializedSignature,
+                    ArrayRef<Type> typeErasedParams,
+                    SILFunction *target, Identifier spiGroup,
+                    const ModuleDecl *spiModule,
                     AvailabilityContext availability);
 };