embedded: don't re-abstract witness method calls for existentials

Don't convert indirect to direct arguments. This is needed to support general existentials in embedded swift.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/Utilities/GenericSpecialization.swift

@@ -148,7 +148,7 @@ func specializeWitnessTable(for conformance: Conformance, _ context: ModulePassC
       guard !methodSubs.conformances.contains(where: {!$0.isValid}),
             context.loadFunction(function: origMethod, loadCalleesRecursively: true),
             let specializedMethod = context.specialize(function: origMethod, for: methodSubs,
-                                                       convertIndirectToDirect: true, isMandatory: true)
+                                                       convertIndirectToDirect: false, isMandatory: true)
       else {
         return origEntry
       }
@@ -215,7 +215,7 @@ private func specializeDefaultMethods(for conformance: Conformance,
       guard !methodSubs.conformances.contains(where: {!$0.isValid}),
             context.loadFunction(function: origMethod, loadCalleesRecursively: true),
             let specializedMethod = context.specialize(function: origMethod, for: methodSubs,
-                                                       convertIndirectToDirect: true, isMandatory: true)
+                                                       convertIndirectToDirect: false, isMandatory: true)
       else {
         return origEntry
       }

include/swift/SILOptimizer/Utils/Generics.h

@@ -216,7 +216,9 @@ class ReabstractionInfo {
 
   ReabstractionInfo(CanSILFunctionType substitutedType,
                     SILDeclRef methodDecl,
+                    bool convertIndirectToDirect,
                     SILModule &M) :
+    ConvertIndirectToDirect(convertIndirectToDirect),
     SubstitutedType(substitutedType),
     methodDecl(methodDecl),
     M(&M), isWholeModule(M.isWholeModule()) {}

lib/SILOptimizer/Utils/Generics.cpp

@@ -2413,7 +2413,8 @@ bool swift::specializeClassMethodInst(ClassMethodInst *cm) {
   SILType substitutedType =
       funcTy.substGenericArgs(m, subs, TypeExpansionContext::minimal());
 
-  ReabstractionInfo reInfo(substitutedType.getAs<SILFunctionType>(), cm->getMember(), m);
+  ReabstractionInfo reInfo(substitutedType.getAs<SILFunctionType>(), cm->getMember(),
+                           /*convertIndirectToDirect=*/ true, m);
   reInfo.createSubstitutedAndSpecializedTypes();
   CanSILFunctionType finalFuncTy = reInfo.getSpecializedType();
   SILType finalSILTy = SILType::getPrimitiveObjectType(finalFuncTy);
@@ -2465,7 +2466,8 @@ bool swift::specializeWitnessMethodInst(WitnessMethodInst *wm) {
   SILType substitutedType =
       funcTy.substGenericArgs(m, subs, TypeExpansionContext::minimal());
 
-  ReabstractionInfo reInfo(substitutedType.getAs<SILFunctionType>(), wm->getMember(), m);
+  ReabstractionInfo reInfo(substitutedType.getAs<SILFunctionType>(), wm->getMember(),
+                           /*convertIndirectToDirect=*/ false, m);
   reInfo.createSubstitutedAndSpecializedTypes();
   CanSILFunctionType finalFuncTy = reInfo.getSpecializedType();
   SILType finalSILTy = SILType::getPrimitiveObjectType(finalFuncTy);