[Serialization] Serialize hasCReferences to keep linkage

lib/Serialization/DeserializeSIL.cpp

@@ -511,14 +511,14 @@ SILDeserializer::readSILFunctionChecked(DeclID FID, SILFunction *existingFn,
   GenericSignatureID genericSigID;
   unsigned rawLinkage, isTransparent, isSerialized, isThunk,
       isWithoutactuallyEscapingThunk, specialPurpose, inlineStrategy,
-      optimizationMode, subclassScope, effect, numSpecAttrs,
+      optimizationMode, subclassScope, hasCReferences, effect, numSpecAttrs,
       hasQualifiedOwnership, isWeakImported, LIST_VER_TUPLE_PIECES(available),
       isDynamic, isExactSelfClass;
   ArrayRef<uint64_t> SemanticsIDs;
   SILFunctionLayout::readRecord(
       scratch, rawLinkage, isTransparent, isSerialized, isThunk,
       isWithoutactuallyEscapingThunk, specialPurpose, inlineStrategy,
-      optimizationMode, subclassScope, effect, numSpecAttrs,
+      optimizationMode, subclassScope, hasCReferences, effect, numSpecAttrs,
       hasQualifiedOwnership, isWeakImported, LIST_VER_TUPLE_PIECES(available),
       isDynamic, isExactSelfClass, funcTyID, replacedFunctionID, genericSigID,
       clangNodeOwnerID, SemanticsIDs);
@@ -639,6 +639,7 @@ SILDeserializer::readSILFunctionChecked(DeclID FID, SILFunction *existingFn,
     fn->setOptimizationMode(OptimizationMode(optimizationMode));
     fn->setAlwaysWeakImported(isWeakImported);
     fn->setClassSubclassScope(SubclassScope(subclassScope));
+    fn->setHasCReferences(bool(hasCReferences));
 
     llvm::VersionTuple available;
     DECODE_VER_TUPLE(available);
@@ -2824,14 +2825,14 @@ bool SILDeserializer::hasSILFunction(StringRef Name,
   GenericSignatureID genericSigID;
   unsigned rawLinkage, isTransparent, isSerialized, isThunk,
       isWithoutactuallyEscapingThunk, isGlobal, inlineStrategy,
-      optimizationMode, subclassScope, effect, numSpecAttrs,
+      optimizationMode, subclassScope, hasCReferences, effect, numSpecAttrs,
       hasQualifiedOwnership, isWeakImported, LIST_VER_TUPLE_PIECES(available),
       isDynamic, isExactSelfClass;
   ArrayRef<uint64_t> SemanticsIDs;
   SILFunctionLayout::readRecord(
       scratch, rawLinkage, isTransparent, isSerialized, isThunk,
       isWithoutactuallyEscapingThunk, isGlobal, inlineStrategy,
-      optimizationMode, subclassScope, effect, numSpecAttrs,
+      optimizationMode, subclassScope, hasCReferences, effect, numSpecAttrs,
       hasQualifiedOwnership, isWeakImported, LIST_VER_TUPLE_PIECES(available),
       isDynamic, isExactSelfClass, funcTyID, replacedFunctionID, genericSigID,
       clangOwnerID, SemanticsIDs);

lib/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 575; // GlobalInitOnceFunction SILFunction purpose
+const uint16_t SWIFTMODULE_VERSION_MINOR = 576; // hasCReferences
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

lib/Serialization/SILFormat.h

@@ -281,6 +281,7 @@ namespace sil_block {
                      BCFixed<2>,  // inlineStrategy
                      BCFixed<2>,  // optimizationMode
                      BCFixed<2>,  // classSubclassScope
+                     BCFixed<1>,  // hasCReferences
                      BCFixed<3>,  // side effect info.
                      BCVBR<8>,    // number of specialize attributes
                      BCFixed<1>,  // has qualified ownership

lib/Serialization/SerializeSIL.cpp

@@ -433,9 +433,9 @@ void SILSerializer::writeSILFunction(const SILFunction &F, bool DeclOnly) {
       Out, ScratchRecord, abbrCode, toStableSILLinkage(Linkage),
       (unsigned)F.isTransparent(), (unsigned)F.isSerialized(),
       (unsigned)F.isThunk(), (unsigned)F.isWithoutActuallyEscapingThunk(),
-      (unsigned)F.getSpecialPurpose(),
-      (unsigned)F.getInlineStrategy(), (unsigned)F.getOptimizationMode(),
-      (unsigned)F.getClassSubclassScope(), (unsigned)F.getEffectsKind(),
+      (unsigned)F.getSpecialPurpose(), (unsigned)F.getInlineStrategy(),
+      (unsigned)F.getOptimizationMode(), (unsigned)F.getClassSubclassScope(),
+      (unsigned)F.hasCReferences(), (unsigned)F.getEffectsKind(),
       (unsigned)numSpecAttrs, (unsigned)F.hasOwnership(),
       F.isAlwaysWeakImported(), LIST_VER_TUPLE_PIECES(available),
       (unsigned)F.isDynamicallyReplaceable(), (unsigned)F.isExactSelfClass(),

test/Serialization/cdecl_attr.swift

@@ -0,0 +1,12 @@
+// RUN: %empty-directory(%t)
+// Ensure .swift -> .ll
+// RUN: %target-swift-frontend -emit-ir %s | %FileCheck %s
+
+// Ensure .swift -> .sib -> .ll
+// RUN: %target-swift-frontend -emit-sib %s -o %t/cdecl_attr.sib
+// RUN: %target-swift-frontend -emit-ir %t/cdecl_attr.sib | %FileCheck %s
+
+// CHECK: define hidden {{.*}} @foo
+
+@_cdecl("foo")
+func foo() {}