Enable access markers at -O when -enforce-exclusivity is explicit.

-enforce-exclusivity=checked now does what it says. It emits checks at -O, not
just -Onone.

This does not change the default.
-Onone default: -enforce-exclusivity=checked
-O default: -enforce-exclusivity=unchecked

Author: atrick

lib/SILOptimizer/Mandatory/AccessMarkerElimination.cpp

@@ -36,7 +36,7 @@ using namespace swift;
 // This is currently unsupported because tail duplication results in
 // address-type block arguments.
 llvm::cl::opt<bool> EnableOptimizedAccessMarkers(
-    "sil-optimized-access-markers", llvm::cl::init(false),
+    "sil-optimized-access-markers", llvm::cl::init(true),
     llvm::cl::desc("Enable memory access markers during optimization passes."));
 
 namespace {

test/SILOptimizer/access_marker_verify.swift

@@ -1,5 +1,6 @@
-// RUN: %target-swift-frontend -enable-verify-exclusivity -enforce-exclusivity=checked -enable-sil-ownership -Onone -emit-silgen -swift-version 4 -parse-as-library %s | %FileCheck %s
+// RUN: %target-swift-frontend -enable-verify-exclusivity -enforce-exclusivity=checked -enable-sil-ownership -emit-silgen -swift-version 4 -parse-as-library %s | %FileCheck %s
 // RUN: %target-swift-frontend -enable-verify-exclusivity -enforce-exclusivity=checked -enable-sil-ownership -Onone -emit-sil -swift-version 4 -parse-as-library %s
+// RUN: %target-swift-frontend -enable-verify-exclusivity -enforce-exclusivity=checked -enable-sil-ownership -O -emit-sil -swift-version 4 -parse-as-library %s
 // REQUIRES: asserts
 
 // Test the combination of SILGen + DiagnoseStaticExclusivity with verification.