diff --git a/mlir/include/mlir/Dialect/GPU/GPUOps.td b/mlir/include/mlir/Dialect/GPU/GPUOps.td
--- a/mlir/include/mlir/Dialect/GPU/GPUOps.td
+++ b/mlir/include/mlir/Dialect/GPU/GPUOps.td
@@ -454,6 +454,10 @@
     /// the operand will be dropped.  The block argument must not have any uses.
     void eraseKernelArgument(unsigned index);
 
+    /// Add the given value as a kernel argument. Returns the corresponding newly
+    /// added BlockArgument.
+    BlockArgument addKernelArgument(Value argument);
+
     static StringRef getBlocksKeyword() { return "blocks"; }
     static StringRef getThreadsKeyword() { return "threads"; }
     static StringRef getArgsKeyword() { return "args"; }
@@ -474,11 +478,14 @@
 
 def GPU_ReturnOp : GPU_Op<"return", [Terminator]>, Arguments<(ins)>,
     Results<(outs)> {
-  let summary = "Terminator for GPU launch regions.";
+  let summary = "Terminator for GPU launch regions and GPU functions.";
   let description = [{
     A terminator operation for regions that appear in the body of `gpu.launch`
-    operation.  These regions are not expected to return any value so the
-    terminator takes no operands.
+    operation and regions that appear in the body of `gpu.func` functions. The
+    operands to the `gpu.return` are the result values returned by an 
+    incovation of the `gpu.func`.
+    As `gpu.launch` does not return any values, it is expected that a
+    corresponding `gpu.return` also has no operands.
   }];
 
   let parser = [{ return success(); }];
diff --git a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
--- a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
+++ b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
@@ -201,6 +201,8 @@
   result.addOperands(
       {gridSizeX, gridSizeY, gridSizeZ, blockSizeX, blockSizeY, blockSizeZ});
   result.addOperands(operands);
+  // We want to be able to add operands later, for instance due to code motion.
+  result.setOperandListToResizable();
 
   // Create a kernel body region with kNumConfigRegionAttributes + N arguments,
   // where the first kNumConfigRegionAttributes arguments have `index` type and
@@ -270,16 +272,16 @@
   }
 
   // Block terminators without successors are expected to exit the kernel region
-  // and must be `gpu.launch`.
+  // and must be `gpu.return`.
   for (Block &block : op.body()) {
     if (block.empty())
       continue;
     if (block.back().getNumSuccessors() != 0)
       continue;
     if (!isa<gpu::ReturnOp>(&block.back())) {
-      return block.back()
-                 .emitError("expected 'gpu.terminator' or a terminator with "
-                            "successors")
+      return (block.back().emitError()
+              << "expected '" << gpu::ReturnOp::getOperationName() << "' or a "
+              << "terminator with successors")
                  .attachNote(op.getLoc())
              << "in '" << LaunchOp::getOperationName() << "' body region";
     }
@@ -449,6 +451,15 @@
   getOperation()->eraseOperand(kNumConfigOperands + index);
 }
 
+BlockArgument LaunchOp::addKernelArgument(Value value) {
+  Block &entryBlock = body().front();
+  Operation *op = getOperation();
+  llvm::SmallVector<Value, 8> operands(op->getOperands());
+  operands.push_back(value);
+  op->setOperands(operands);
+  return entryBlock.addArgument(value.getType());
+}
+
 namespace {
 // Clone any known constants passed as operands to the kernel into its body.
 class PropagateConstantBounds : public OpRewritePattern<LaunchOp> {
diff --git a/mlir/test/Dialect/GPU/invalid.mlir b/mlir/test/Dialect/GPU/invalid.mlir
--- a/mlir/test/Dialect/GPU/invalid.mlir
+++ b/mlir/test/Dialect/GPU/invalid.mlir
@@ -79,7 +79,7 @@
   // @expected-note@+1 {{in 'gpu.launch' body region}}
   gpu.launch blocks(%bx, %by, %bz) in (%sbx = %sz, %sby = %sz, %sbz = %sz)
              threads(%tx, %ty, %tz) in (%stx = %sz, %sty = %sz, %stz = %sz) {
-    // @expected-error@+1 {{expected 'gpu.terminator' or a terminator with successors}}
+    // @expected-error@+1 {{expected 'gpu.return' or a terminator with successors}}
     return
   }
   return