[coverage] Block coverage with support for IfStatements

test/mjsunit/code-coverage-block.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --no-always-opt --block-coverage

[Michael Starzinger, 2017/06/06 11:49:32]

question: Why --no-always-opt here? Do the expected counts start to mismatch in
presence of deopt? Because that would be something worth keeping track of or
commenting on.

[jgruber, 2017/06/06 14:52:46]

--no-always-opt is inherited from the ad-hoc/precise coverage mode tests
(code-coverage-{ad-hoc,precise}). Passing --always-opt makes counts for the
top-level function disappear (see below).

I'm not sure why that happens.. Maybe there's some sort of special handling for
FeedbackVectors of top-level functions?

[jgruber, 2017/06/06 15:06:33]

Brief investigation: The top-level FeedbackVector exists, but its invocation
count is 0. As discussed offline, I'll land this as-is for now. Opened
http://crbug.com/v8/6466 for investigation.

+
+// Test precise code coverage.
+
+function GetCoverage(source) {
+  for (var script of %DebugCollectCoverage()) {
+    if (script.script.source == source) return script;
+  }
+  return undefined;
+}
+
+function TestCoverage(name, source, expectation) {
+  source = source.trim();
+  eval(source);
+  %CollectGarbage("collect dead objects");
+  var coverage = GetCoverage(source);
+  var result = JSON.stringify(coverage);
+  print(result);
+  assertEquals(JSON.stringify(expectation), result, name + " failed");
+}
+
+%DebugToggleBlockCoverage(true);
+
+TestCoverage(
+"call an IIFE",
+`
+(function f() {})();
+`,
+[{"start":0,"end":20,"count":1},{"start":1,"end":16,"count":1}]

[jgruber, 2017/06/06 14:52:46]

With --always-opt, the result is [{"start":1,"end":16,"count":1}] instead.

+);
+
+TestCoverage(
+"call locally allocated function",
+`
+for (var i = 0; i < 10; i++) {
+  let f = () => 1;
+  i += f();
+}
+`,
+[{"start":0,"end":63,"count":1},{"start":41,"end":48,"count":5}]
+);
+
+TestCoverage(
+"if statements",
+`
+function g() {}
+function f(x) {
+  if (x == 42) {
+    if (x == 43) g(); else g();
+  }
+  if (x == 42) { g(); } else { g(); }
+  if (x == 42) g(); else g();
+  if (false) g(); else g();
+  if (false) g();
+  if (true) g(); else g();
+  if (true) g();
+}
+f(42);
+f(43);
+`,
+[{"start":0,"end":258,"count":1},
+ {"start":0,"end":15,"count":11},
+ {"start":16,"end":244,"count":2},
+ {"start":45,"end":83,"count":1},
+ {"start":64,"end":69,"count":0},
+ {"start":71,"end":79,"count":1},
+ {"start":98,"end":107,"count":1},
+ {"start":109,"end":121,"count":1},
+ {"start":136,"end":141,"count":1},
+ {"start":143,"end":151,"count":1},
+ {"start":164,"end":169,"count":0},
+ {"start":171,"end":179,"count":2},
+ {"start":192,"end":197,"count":0},
+ {"start":209,"end":214,"count":2},
+ {"start":216,"end":224,"count":0},
+ {"start":236,"end":241,"count":2}]
+);
+
+%DebugToggleBlockCoverage(false);