Preserve the Implicit attribute in SILLocation. (NFC)

This change aims at reducing the need for SIL passes to check into the AST
storage of SILLocations. The end goal is to eventually merge this with the
autogenerated flag, but at the moment the emergent semantics of both properties
are not identical.

Author: adrian-prantl

include/swift/SIL/SILLocation.h

@@ -175,7 +175,7 @@ class SILLocation {
   union KindAndFlags {
     KindAndFlags() : packedKindAndFlags(0) {}
     KindAndFlags(LocationKind kind, StorageKind storageKind)
-        : fields({kind, storageKind, 0, 0}) {
+      : fields({kind, storageKind, 0, 0, 0}) {
       assert(fields.kind == kind && "LocationKind overflow");
       assert(fields.storageKind == storageKind && "StorageKind overflow");
     }
@@ -186,6 +186,7 @@ class SILLocation {
       uint8_t kind: 3;
       uint8_t storageKind: 2;
       uint8_t autoGenerated: 1;
+      uint8_t implicit: 1;
       uint8_t inPrologue: 1;
     } fields;
   };
@@ -270,8 +271,7 @@ class SILLocation {
       : storage(ext), kindAndFlags(K, ExtendedASTNodeKind) {
   }
 
-  SILLocation(SourceLoc L, LocationKind K)
-      : storage(L), kindAndFlags(K, SourceLocKind) {}
+  SILLocation(SourceLoc L, LocationKind K);
 
   // Used by SILInstruction.
   SILLocation(Storage storage, uint8_t packedKindAndFlags) :
@@ -284,10 +284,10 @@ class SILLocation {
   //
   // It is okay to pass a nullptr to these constructors, but preferably, a
   // null-location should be created with `invalid()`.
-  SILLocation(Stmt *S) : SILLocation(ASTNodeTy(S), RegularKind) {}
-  SILLocation(Expr *E) : SILLocation(ASTNodeTy(E), RegularKind) {}
-  SILLocation(Decl *D) : SILLocation(ASTNodeTy(D), RegularKind) {}
-  SILLocation(Pattern *P) : SILLocation(ASTNodeTy(P), RegularKind) {}
+  SILLocation(Stmt *S);
+  SILLocation(Expr *E);
+  SILLocation(Decl *D);
+  SILLocation(Pattern *P);
 
   /// Returns a null location.
   static SILLocation invalid() { return SILLocation(); }
@@ -354,6 +354,11 @@ class SILLocation {
   /// body, such as thunks or default destructors.
   bool isAutoGenerated() const { return kindAndFlags.fields.autoGenerated; }
 
+  /// Returns true if the location was created from an implicit AST node.
+  /// TODO: This is very similar to autogenerated,
+  ///       and these two properties should be merged.
+  bool isImplicit() const { return kindAndFlags.fields.implicit; }
+
   /// Returns false if the location should be represented in debuginfo.
   bool isHiddenFromDebugInfo() const {
     return isAutoGenerated() && !hasASTNodeForDebugging();

lib/SIL/IR/SILLocation.cpp

@@ -25,8 +25,33 @@ using namespace swift;
 static_assert(sizeof(SILLocation) <= 2 * sizeof(void *),
               "SILLocation must stay small");
 
-SILLocation::FilenameAndLocation *SILLocation::FilenameAndLocation::
-alloc(unsigned line, unsigned column, StringRef filename, SILModule &module) {
+SILLocation::SILLocation(Stmt *S) : SILLocation(ASTNodeTy(S), RegularKind) {
+  if (S->isImplicit())
+    kindAndFlags.fields.implicit = true;
+}
+
+SILLocation::SILLocation(Expr *E) : SILLocation(ASTNodeTy(E), RegularKind) {
+  if (E->isImplicit())
+    kindAndFlags.fields.implicit = true;
+}
+SILLocation::SILLocation(Decl *D) : SILLocation(ASTNodeTy(D), RegularKind) {
+  if (D && D->isImplicit())
+    kindAndFlags.fields.implicit = true;
+}
+
+SILLocation::SILLocation(Pattern *P) : SILLocation(ASTNodeTy(P), RegularKind) {
+  if (P->isImplicit())
+    kindAndFlags.fields.implicit = true;
+}
+
+SILLocation::SILLocation(SourceLoc L, LocationKind K)
+    : storage(L), kindAndFlags(K, SourceLocKind) {
+  kindAndFlags.fields.implicit = true;
+}
+
+SILLocation::FilenameAndLocation *
+SILLocation::FilenameAndLocation::alloc(unsigned line, unsigned column,
+                                        StringRef filename, SILModule &module) {
   return new (module) FilenameAndLocation(line, column, filename);
 }
 
@@ -210,6 +235,7 @@ void SILLocation::dump() const {
   }
 
   if (isAutoGenerated()) llvm::dbgs() << ":auto";
+  if (isImplicit())      llvm::dbgs() << ":implicit";
   if (pointsToEnd())     llvm::dbgs() << ":end";
   if (isInPrologue())    llvm::dbgs() << ":prologue";
   if (isSILFile())       llvm::dbgs() << ":sil";

lib/SILOptimizer/Mandatory/DiagnoseUnreachable.cpp

@@ -647,16 +647,8 @@ static bool isUserCode(const SILInstruction *I) {
 
   // If the instruction corresponds to user-written return or some other
   // statement, we know it corresponds to user code.
-  if (Loc.is<RegularLocation>() || Loc.is<ReturnLocation>()) {
-    if (auto *E = Loc.getAsASTNode<Expr>())
-      return !E->isImplicit();
-    if (auto *D = Loc.getAsASTNode<Decl>())
-      return !D->isImplicit();
-    if (auto *S = Loc.getAsASTNode<Stmt>())
-      return !S->isImplicit();
-    if (auto *P = Loc.getAsASTNode<Pattern>())
-      return !P->isImplicit();
-  }
+  if (Loc.is<RegularLocation>() || Loc.is<ReturnLocation>())
+    return !Loc.isImplicit();
   return false;
 }