[sil] Add a SILDeclRef field to SILFunction, have SILGen set it, and teach SILFunction how to use the field to get the SourceFile associated with the SILFunction.

(cherry picked from commit 025902f)

Author: gottesmm

include/swift/SIL/SILFunction.h

@@ -269,6 +269,9 @@ class SILFunction
   /// @_dynamicReplacement(for:) function.
   SILFunction *ReplacedFunction = nullptr;
 
+  /// The SILDeclRef that this function was created for by SILGen if one exists.
+  SILDeclRef DeclRef = SILDeclRef();
+
   /// This SILFunction REFerences an ad-hoc protocol requirement witness in
   /// order to keep it alive, such that it main be obtained in IRGen. Without
   /// this explicit reference, the witness would seem not-used, and not be
@@ -1114,6 +1117,12 @@ class SILFunction
   /// Get the source location of the function.
   const SILDebugScope *getDebugScope() const { return DebugScope; }
 
+  /// Return the SILDeclRef for this SILFunction if one was assigned by SILGen.
+  SILDeclRef getDeclRef() const { return DeclRef; }
+
+  /// Set the SILDeclRef for this SILFunction. Used mainly by SILGen.
+  void setDeclRef(SILDeclRef declRef) { DeclRef = declRef; }
+
   /// Get this function's bare attribute.
   IsBare_t isBare() const { return IsBare_t(Bare); }
   void setBare(IsBare_t isB) { Bare = isB; }
@@ -1376,6 +1385,9 @@ class SILFunction
 
   ActorIsolation getActorIsolation() const { return actorIsolation; }
 
+  /// Return the source file that this SILFunction belongs to if it exists.
+  SourceFile *getSourceFile() const;
+
   //===--------------------------------------------------------------------===//
   // Block List Access
   //===--------------------------------------------------------------------===//

lib/SIL/IR/SILFunction.cpp

@@ -1189,3 +1189,11 @@ bool SILFunction::argumentMayRead(Operand *argOp, SILValue addr) {
 
   return argumentMayReadFunction({this}, {argOp}, {addr});
 }
+
+SourceFile *SILFunction::getSourceFile() const {
+  auto declRef = getDeclRef();
+  if (!declRef)
+    return nullptr;
+
+  return declRef.getInnermostDeclContext()->getParentSourceFile();
+}

lib/SILGen/SILGen.cpp

@@ -1236,6 +1236,9 @@ void SILGenModule::preEmitFunction(SILDeclRef constant, SILFunction *F,
   // Create a debug scope for the function using astNode as source location.
   F->setDebugScope(new (M) SILDebugScope(Loc, F));
 
+  // Initialize F with the constant we created for it.
+  F->setDeclRef(constant);
+
   LLVM_DEBUG(llvm::dbgs() << "lowering ";
              F->printName(llvm::dbgs());
              llvm::dbgs() << " : ";