[spirv] Require source location for createReturnValue.

tools/clang/include/clang/SPIRV/SpirvBuilder.h

@@ -371,7 +371,7 @@ public:
   /// \brief Creates a return instruction.
   void createReturn(SourceLocation loc = {});
   /// \brief Creates a return value instruction.
-  void createReturnValue(SpirvInstruction *value, SourceLocation loc = {});
+  void createReturnValue(SpirvInstruction *value, SourceLocation);
 
   /// \brief Creates an OpExtInst instruction with the given instruction set,
   /// instruction number, and operands. Returns the resulting instruction

tools/clang/lib/SPIRV/SpirvEmitter.cpp

@@ -1059,6 +1059,7 @@ void SpirvEmitter::doFunctionDecl(const FunctionDecl *decl) {
     // basic block. Make sure we have a termination instruction.
     if (!spvBuilder.isCurrentBasicBlockTerminated()) {
       const auto retType = decl->getReturnType();
+      const auto returnLoc = decl->getBody()->getLocEnd();
 
       if (retType->isVoidType()) {
         spvBuilder.createReturn();
@@ -1066,7 +1067,8 @@ void SpirvEmitter::doFunctionDecl(const FunctionDecl *decl) {
         // If the source code does not provide a proper return value for some
         // control flow path, it's undefined behavior. We just return null
         // value here.
-        spvBuilder.createReturnValue(spvBuilder.getConstantNull(retType));
+        spvBuilder.createReturnValue(spvBuilder.getConstantNull(retType),
+                                     returnLoc);
       }
     }
   }