MandatoryPerformanceOptimizations: fix the linkage of function-signature-specialized functions

We need to keep the original linkage because it would be illegal to call a shared not-serialized function from a serialized function.

Also, rename the API to create the specialized function.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/PassManager/ModulePassContext.swift

@@ -131,7 +131,7 @@ struct ModulePassContext : Context, CustomStringConvertible {
     return function.isDefinition
   }
 
-  func createSpecializedFunctionDeclaration(
+  func createEmptyFunction(
     name: String,
     parameters: [ParameterInfo],
     hasSelfParameter: Bool,
@@ -140,8 +140,8 @@ struct ModulePassContext : Context, CustomStringConvertible {
     return name._withBridgedStringRef { nameRef in
       let bridgedParamInfos = parameters.map { $0._bridged }
       return bridgedParamInfos.withUnsafeBufferPointer { paramBuf in
-        _bridged.createSpecializedFunction(nameRef, paramBuf.baseAddress, paramBuf.count,
-                                           hasSelfParameter, originalFunction.bridged).function
+        _bridged.createEmptyFunction(nameRef, paramBuf.baseAddress, paramBuf.count,
+                                     hasSelfParameter, originalFunction.bridged).function
       }
     }
   }

SwiftCompilerSources/Sources/Optimizer/Utilities/FunctionSignatureTransforms.swift

@@ -82,7 +82,7 @@ private func createSpecializedFunction(
 ) -> Function {
   let (aliveParameters, hasSelfParameter) = getAliveParameters(of: originalFunction)
 
-  let specializedFunction = context.createSpecializedFunctionDeclaration(
+  let specializedFunction = context.createEmptyFunction(
     name: name,
     parameters: aliveParameters,
     hasSelfParameter: hasSelfParameter,

include/swift/SILOptimizer/OptimizerBridging.h

@@ -286,11 +286,11 @@ struct BridgedPassContext {
   SWIFT_IMPORT_UNSAFE OptionalBridgedFunction lookUpNominalDeinitFunction(BridgedNominalTypeDecl nominal) const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedSubstitutionMap getContextSubstitutionMap(BridgedType type) const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedType getBuiltinIntegerType(SwiftInt bitWidth) const;
-  SWIFT_IMPORT_UNSAFE BridgedFunction createSpecializedFunction(BridgedStringRef name,
-                                                                const BridgedParameterInfo * _Nullable bridgedParams,
-                                                                SwiftInt paramCount,
-                                                                bool hasSelfParam,
-                                                                BridgedFunction fromFunc) const;
+  SWIFT_IMPORT_UNSAFE BridgedFunction createEmptyFunction(BridgedStringRef name,
+                                                          const BridgedParameterInfo * _Nullable bridgedParams,
+                                                          SwiftInt paramCount,
+                                                          bool hasSelfParam,
+                                                          BridgedFunction fromFunc) const;
   void moveFunctionBody(BridgedFunction sourceFunc, BridgedFunction destFunc) const;
 
   // Passmanager housekeeping

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -1731,11 +1731,11 @@ bool BridgedPassContext::enableSimplificationFor(BridgedInstruction inst) const
 }
 
 BridgedFunction BridgedPassContext::
-createSpecializedFunction(BridgedStringRef name,
-                          const BridgedParameterInfo * _Nullable bridgedParams,
-                          SwiftInt paramCount,
-                          bool hasSelfParam,
-                          BridgedFunction fromFunc) const {
+createEmptyFunction(BridgedStringRef name,
+                    const BridgedParameterInfo * _Nullable bridgedParams,
+                    SwiftInt paramCount,
+                    bool hasSelfParam,
+                    BridgedFunction fromFunc) const {
   swift::SILModule *mod = invocation->getPassManager()->getModule();
   SILFunction *fromFn = fromFunc.getFunction();
 
@@ -1761,7 +1761,7 @@ createSpecializedFunction(BridgedStringRef name,
   SILOptFunctionBuilder functionBuilder(*invocation->getTransform());
 
   SILFunction *newF = functionBuilder.createFunction(
-    SILLinkage::Shared, name.unbridged(), newTy, nullptr, fromFn->getLocation(), fromFn->isBare(),
+    fromFn->getLinkage(), name.unbridged(), newTy, nullptr, fromFn->getLocation(), fromFn->isBare(),
     fromFn->isTransparent(), fromFn->isSerialized(), IsNotDynamic, IsNotDistributed,
     IsNotRuntimeAccessible, fromFn->getEntryCount(), fromFn->isThunk(),
     fromFn->getClassSubclassScope(), fromFn->getInlineStrategy(), fromFn->getEffectsKind(),