Serialize and deserialize implicit flag in SourceLocs. Also, skip

emitting unreachable block diagnostic for deserialized instructions as
it was suppressed already in the past as instructions were deserialized
as implicit by default

Author: usama54321

include/swift/SIL/SILLocation.h

@@ -263,6 +263,12 @@ class SILLocation {
     assert(filePos && !filePos->filename.empty());
   }
 
+  SILLocation(FilenameAndLocation *filePos, LocationKind K, bool Implicit)
+      : storage(filePos), kindAndFlags(K, FilenameAndLocationKind) {
+    assert(filePos && !filePos->filename.empty());
+    kindAndFlags.fields.implicit = Implicit;
+  }
+
   // It is okay to pass a nullptr, but preferably, a null-location should be
   // created with `invalid()`.
   SILLocation(ASTNodeTy Node, LocationKind K)
@@ -552,6 +558,8 @@ class RegularLocation : public SILLocation {
       : SILLocation(L, RegularKind, Implicit) {}
   RegularLocation(FilenameAndLocation *filePos)
     : SILLocation(filePos, RegularKind) {}
+  RegularLocation(FilenameAndLocation *filePos, bool Implicit)
+    : SILLocation(filePos, RegularKind, Implicit) {}
 
   /// Convert \p loc to a RegularLocation.
   explicit RegularLocation(SILLocation loc) : SILLocation(loc, RegularKind) {}
@@ -622,6 +630,9 @@ class ReturnLocation : public SILLocation {
   ReturnLocation(FilenameAndLocation *filePos)
     : SILLocation(filePos, ReturnKind) {}
 
+  ReturnLocation(FilenameAndLocation *filePos, bool Implicit)
+    : SILLocation(filePos, ReturnKind, Implicit) {}
+
   static bool isKind(const SILLocation& L) {
     return L.getKind() == ReturnKind;
   }
@@ -643,6 +654,9 @@ class ImplicitReturnLocation : public SILLocation {
   ImplicitReturnLocation(FilenameAndLocation *filePos)
     : SILLocation(filePos, ImplicitReturnKind) {}
 
+  ImplicitReturnLocation(FilenameAndLocation *filePos, bool Implicit)
+    : SILLocation(filePos, ImplicitReturnKind, Implicit) {}
+
   /// Convert \p loc to an ImplicitReturnLocation.
   explicit ImplicitReturnLocation(SILLocation Loc);
 

lib/SILOptimizer/Mandatory/DiagnoseUnreachable.cpp

@@ -994,6 +994,15 @@ static bool diagnoseUnreachableBlock(
     if (Loc.is<ImplicitReturnLocation>() || Loc.isAutoGenerated())
       return false;
 
+    // Without debug info serialization, source locations are deserialized as
+    // implicit by default and as a result this diagnostic is never produced on
+    // deserialized code.  With support for serializing debug info/source
+    // locations, the implicit flag is deserialized properly .  However, this
+    // creates new diagnostic warnings in many tests. Until these tests are
+    // fixed, we suppress these warnings to match existing behavior.
+    if (Loc.isFilenameAndLocation())
+      continue;
+
     // Check if the instruction corresponds to user-written code, also make
     // sure we don't report an error twice for the same instruction.
     if (isUserCode(&*I) && !State->BlocksWithErrors.contains(&B)) {

lib/Serialization/DeserializeSIL.cpp

@@ -396,32 +396,36 @@ SILDeserializer::readNextRecord(SmallVectorImpl<uint64_t> &scratch) {
 
 std::optional<SILLocation> SILDeserializer::readLoc(unsigned kind,
                                      SmallVectorImpl<uint64_t> &scratch) {
-  uint8_t LocationKind = 0;
+  unsigned LocationKind = 0, Implicit;
   SILLocation::FilenameAndLocation *FNameLoc = nullptr;
   if (kind == SIL_SOURCE_LOC_REF) {
     ValueID LocID;
-    SourceLocRefLayout::readRecord(scratch, LocID, LocationKind);
+    SourceLocRefLayout::readRecord(scratch, LocID, LocationKind, Implicit);
     if (LocID == 0)
       return std::optional<SILLocation>();
-    FNameLoc = ParsedLocs[LocID];
+    FNameLoc = ParsedLocs[LocID - 1];
   } else {
     ValueID Row = 0, Col = 0, FNameID = 0;
-    SourceLocLayout::readRecord(scratch, Row, Col, FNameID, LocationKind);
+    SourceLocLayout::readRecord(scratch, Row, Col, FNameID, LocationKind, Implicit);
 
 
     FNameLoc = SILLocation::FilenameAndLocation::alloc(
         Row, Col, MF->getIdentifierText(FNameID), SILMod);
 
-    ParsedLocs.insert({ParsedLocs.size() + 1, FNameLoc});
+    ParsedLocs.push_back(FNameLoc);
   }
 
+  // FIXME: Instructions are being deserialized as implicit as existing code in
+  // readSILInstruction also deserializes instructions as implicit by default.
+  // This suppresses some diagnostics which otherwise break tests. This should
+  // be fixed in both places
   switch(LocationKind) {
     case SILLocation::ReturnKind:
-      return ReturnLocation(FNameLoc);
+      return ReturnLocation(FNameLoc, Implicit);
     case SILLocation::ImplicitReturnKind:
-      return ImplicitReturnLocation(FNameLoc);
+      return ImplicitReturnLocation(FNameLoc, Implicit);
     default:
-      return RegularLocation(FNameLoc);
+      return RegularLocation(FNameLoc, Implicit);
   }
 }
 

lib/Serialization/DeserializeSIL.h

@@ -153,7 +153,7 @@ namespace swift {
     std::optional<SILLocation> readLoc(unsigned kind, SmallVectorImpl<uint64_t> &scratch);
 
     llvm::DenseMap<unsigned, const SILDebugScope *> ParsedScopes;
-    llvm::DenseMap<unsigned, SILLocation::FilenameAndLocation *> ParsedLocs;
+    llvm::SmallVector<SILLocation::FilenameAndLocation *> ParsedLocs;
 
     SILFunction *getFuncForReference(StringRef Name, SILType Ty, TypeExpansionContext context);
     SILFunction *getFuncForReference(StringRef Name, bool forDebugScope = false);

lib/Serialization/SILFormat.h

@@ -317,13 +317,15 @@ namespace sil_block {
     ValueIDField,
     ValueIDField,
     ValueIDField,
-    BCFixed<8> /// LocationKind
+    BCFixed<3>, /// LocationKind
+    BCFixed<1> /// Implicit
   >;
 
   using SourceLocRefLayout = BCRecordLayout<
     SIL_SOURCE_LOC_REF,
     ValueIDField,
-    BCFixed<8>
+    BCFixed<3>,
+    BCFixed<1> /// Implicit
   >;
 
   using SILFunctionLayout =

lib/Serialization/SerializeSIL.cpp

@@ -3102,7 +3102,7 @@ void SILSerializer::writeSourceLoc(SILLocation Loc, const SourceManager &SM) {
   if (SourceLocMap.find(OpaquePtr) != SourceLocMap.end()) {
     SourceLocRefLayout::emitRecord(Out, ScratchRecord,
                                    SILAbbrCodes[SourceLocRefLayout::Code],
-                                   SourceLocMap[OpaquePtr], LocationKind);
+                                   SourceLocMap[OpaquePtr], LocationKind, (unsigned)Loc.isImplicit());
     return;
   }
 
@@ -3112,7 +3112,7 @@ void SILSerializer::writeSourceLoc(SILLocation Loc, const SourceManager &SM) {
 
   if (!SLoc.isValid()) {
     //emit empty source loc
-    SourceLocRefLayout::emitRecord(Out, ScratchRecord, SILAbbrCodes[SourceLocRefLayout::Code], 0, 0);
+    SourceLocRefLayout::emitRecord(Out, ScratchRecord, SILAbbrCodes[SourceLocRefLayout::Code], 0, 0, (unsigned)0);
     return;
   }
 
@@ -3121,7 +3121,7 @@ void SILSerializer::writeSourceLoc(SILLocation Loc, const SourceManager &SM) {
   SourceLocMap.insert({OpaquePtr, SourceLocMap.size() + 1});
   SourceLocLayout::emitRecord(Out, ScratchRecord,
                               SILAbbrCodes[SourceLocLayout::Code], Row, Column,
-                              FNameID, LocationKind);
+                              FNameID, LocationKind, (unsigned)Loc.isImplicit());
 }
 
 void SILSerializer::writeDebugScopes(const SILDebugScope *Scope,