diff --git a/src/tcompiler.cpp b/src/tcompiler.cpp
index 612237cb..6e76c3ec 100644
--- a/src/tcompiler.cpp
+++ b/src/tcompiler.cpp
@@ -1140,14 +1140,14 @@ struct CCallingConv {
 
         return Argument(C_AGGREGATE_REG, t, StructType::get(*CU->TT->ctx, elements));
     }
-    void Classify(Obj *ftype, Obj *params, Classification *info) {
+    void Classify(Obj *ftype, CallingConv::ID cconv, Obj *params, Classification *info) {
         Obj fparams, returntype;
         ftype->obj("parameters", &fparams);
         ftype->obj("returntype", &returntype);
         int zero = 0;
         info->returntype = ClassifyArgument(&returntype, &zero, &zero, true);
 
-        if (return_empty_struct_as_void) {
+        if (return_empty_struct_as_void || cconv == CallingConv::SPIR_KERNEL) {
             // windows classifies empty structs as pass by pointer, but we need a return
             // value of unit (an empty tuple) to be translated to void. So if it is unit,
             // force the return value to be void by overriding the normal classification
@@ -1173,13 +1173,13 @@ struct CCallingConv {
                 CreateFunctionType(info, fparams.size(), ftype->boolean("isvararg"));
     }
 
-    Classification *ClassifyFunction(Obj *fntyp) {
+    Classification *ClassifyFunction(Obj *fntyp, CallingConv::ID cconv) {
         Classification *info = (Classification *)CU->symbols->getud(fntyp);
         if (!info) {
             info = new Classification();  // TODO: fix leak
             Obj params;
             fntyp->obj("parameters", &params);
-            Classify(fntyp, &params, info);
+            Classify(fntyp, cconv, &params, info);
             CU->symbols->setud(fntyp, info);
         }
         return info;
@@ -1291,8 +1291,9 @@ struct CCallingConv {
         }
     }
 
-    Function *CreateFunction(Module *M, Obj *ftype, const Twine &name) {
-        Classification *info = ClassifyFunction(ftype);
+    Function *CreateFunction(Module *M, Obj *ftype, CallingConv::ID cconv,
+                             const Twine &name) {
+        Classification *info = ClassifyFunction(ftype, cconv);
         Function *fn = Function::Create(info->fntype, Function::InternalLinkage, name, M);
         AttributeFnOrCall(fn, info);
         return fn;
@@ -1323,7 +1324,7 @@ struct CCallingConv {
     }
     void EmitEntry(IRBuilder<> *B, Obj *ftype, Function *func,
                    std::vector<Value *> *variables) {
-        Classification *info = ClassifyFunction(ftype);
+        Classification *info = ClassifyFunction(ftype, func->getCallingConv());
         assert(info->paramtypes.size() == variables->size());
         Function::arg_iterator ai = func->arg_begin();
         if (info->returntype.kind == C_AGGREGATE_MEM)
@@ -1371,7 +1372,7 @@ struct CCallingConv {
         }
     }
     void EmitReturn(IRBuilder<> *B, Obj *ftype, Function *function, Value *result) {
-        Classification *info = ClassifyFunction(ftype);
+        Classification *info = ClassifyFunction(ftype, function->getCallingConv());
         ArgumentKind kind = info->returntype.kind;
 
         if (C_AGGREGATE_REG == kind &&
@@ -1432,10 +1433,10 @@ struct CCallingConv {
         }
     }
 
-    Value *EmitCall(IRBuilder<> *B, Obj *ftype, Obj *paramtypes, Value *callee,
-                    std::vector<Value *> *actuals) {
+    Value *EmitCall(IRBuilder<> *B, Obj *ftype, CallingConv::ID cconv, Obj *paramtypes,
+                    Value *callee, std::vector<Value *> *actuals) {
         Classification info;
-        Classify(ftype, paramtypes, &info);
+        Classify(ftype, cconv, paramtypes, &info);
 
         std::vector<Value *> arguments;
 
@@ -1879,16 +1880,25 @@ struct FunctionEmitter {
                 if (fstate->func) return fstate;
             }
 
+            CallingConv::ID callingconv = CallingConv::MaxID;
+            if (funcobj->hasfield("callingconv")) {
+                callingconv = ParseCallingConv(funcobj->string("callingconv"));
+            }
+
             Obj ftype;
             funcobj->obj("type", &ftype);
             // function name is $+name so that it can't conflict with any symbols imported
             // from the C namespace
-            fstate->func = CC->CreateFunction(
-                    M, &ftype, Twine(StringRef((isextern) ? "" : "$"), name));
+            fstate->func =
+                    CC->CreateFunction(M, &ftype, callingconv,
+                                       Twine(StringRef((isextern) ? "" : "$"), name));
             if (isextern) {
                 // Set external linkage for extern functions.
                 fstate->func->setLinkage(GlobalValue::ExternalLinkage);
             }
+            if (callingconv != CallingConv::MaxID) {
+                fstate->func->setCallingConv(callingconv);
+            }
 
             if (funcobj->hasfield("alwaysinline")) {
                 if (funcobj->boolean("alwaysinline")) {
@@ -1903,10 +1913,6 @@ struct FunctionEmitter {
                     fstate->func->addFnAttr(Attribute::NoInline);
                 }
             }
-            if (funcobj->hasfield("callingconv")) {
-                const char *callingconv = funcobj->string("callingconv");
-                fstate->func->setCallingConv(ParseCallingConv(callingconv));
-            }
             if (funcobj->hasfield("noreturn")) {
                 if (funcobj->boolean("noreturn")) {
                     fstate->func->addFnAttr(Attribute::NoReturn);
@@ -3217,6 +3223,11 @@ struct FunctionEmitter {
 
         call->obj("value", &func);
 
+        CallingConv::ID callingconv = CallingConv::MaxID;
+        if (func.hasfield("callingconv")) {
+            callingconv = ParseCallingConv(func.string("callingconv"));
+        }
+
         Value *fn = emitExp(&func);
 
         Obj fnptrtyp;
@@ -3232,7 +3243,7 @@ struct FunctionEmitter {
             setInsertBlock(bb);
             deferred.push_back(bb);
         }
-        Value *r = CC->EmitCall(B, &fntyp, &paramtypes, fn, &actuals);
+        Value *r = CC->EmitCall(B, &fntyp, callingconv, &paramtypes, fn, &actuals);
         setInsertBlock(cur);  // defer may have changed it
         return r;
     }