tint/SingleEntryPoint: Handle diagnostic directive

Add some E2E tests to make sure that we actually produce valid code
for each backend when diagnostic filtering is present.

Bug: tint:1809
Change-Id: I5e903ac0d2ca385967211bb889f86cb85de8f418
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/117590
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/transform/single_entry_point.cc

@@ -114,6 +114,7 @@ Transform::ApplyResult SingleEntryPoint::Apply(const Program* src,
                 }
             },
             [&](const ast::Enable* ext) { b.AST().AddEnable(ctx.Clone(ext)); },
+            [&](const ast::DiagnosticControl* dc) { b.AST().AddDiagnosticControl(ctx.Clone(dc)); },
             [&](Default) {
                 TINT_UNREACHABLE(Transform, b.Diagnostics())
                     << "unhandled global declaration: " << decl->TypeInfo().name;

src/tint/transform/single_entry_point_test.cc

@@ -611,5 +611,25 @@ fn main() {
     EXPECT_EQ(expect, str(got));
 }
 
+TEST_F(SingleEntryPointTest, Directives) {
+    // Make sure that directives are preserved.
+    auto* src = R"(
+enable f16;
+diagnostic(off, derivative_uniformity);
+
+@compute @workgroup_size(1)
+fn main() {
+}
+)";
+
+    SingleEntryPoint::Config cfg("main");
+
+    DataMap data;
+    data.Add<SingleEntryPoint::Config>(cfg);
+    auto got = Run<SingleEntryPoint>(src, data);
+
+    EXPECT_EQ(src, str(got));
+}
+
 }  // namespace
 }  // namespace tint::transform