[Test] Added swift test for ShrinkBorrowScope.

The new file tests the -O pipeline up to just before OSSA lowering.  It
will be used for verifying the effects of ShrinkBorrowScope on swift
code directly, to complement the tests done on SIL by just running a
single pass.

Author: nate-chandler

test/SILOptimizer/shrink_borrow_scope.swift

@@ -0,0 +1,40 @@
+// RUN: %target-swift-frontend -c -O -enable-copy-propagation=true -enable-lexical-lifetimes=true -sil-verify-all -Xllvm -sil-print-final-ossa-module %s | %FileCheck %s
+
+// =============================================================================
+// = DECLARATIONS                                                             {{
+// =============================================================================
+
+@_silgen_name("consumeAndProduce")
+func consumeAndProduce(_ arg: __owned AnyObject) -> AnyObject
+
+// =============================================================================
+// = DECLARATIONS                                                             }}
+// =============================================================================
+
+// =============================================================================
+// = TESTS                                                                    {{
+// =============================================================================
+
+@_silgen_name("eliminate_copy_of_returned_then_consumed_owned_value")
+public func eliminate_copy_of_returned_then_consumed_owned_value(arg: __owned AnyObject) {
+  // CHECK-LABEL: sil [ossa] @eliminate_copy_of_returned_then_consumed_owned_value : {{.*}} {
+  // CHECK:       {{bb[0-9]+}}([[ARG:%[^,]+]] : @owned $AnyObject):
+  // retain arg
+  // CHECK:       [[ARG_LIFETIME:%[^,]+]] = begin_borrow [lexical] [[ARG]]
+  // CHECK:       [[ARG_COPY:%[^,]+]] = copy_value [[ARG_LIFETIME]]
+  let x = consumeAndProduce(arg)
+  // CHECK:       [[X:%[^,]+]] = apply {{%[^,]+}}([[ARG_COPY]])
+  // no copy of 'x'
+  _ = consumeAndProduce(x)
+  // CHECK:       [[RESULT:%[^,]+]] = apply {{%[^,]+}}([[X]])
+  // CHECK:       end_borrow [[ARG_LIFETIME]]
+  // release result
+  // release arg
+  // CHECK:       destroy_value [[RESULT]]
+  // CHECK:       destroy_value [[ARG]]
+  // CHECK-LABEL: } // end sil function 'eliminate_copy_of_returned_then_consumed_owned_value'
+}
+
+// =============================================================================
+// = TESTS                                                                    }}
+// =============================================================================