[turbofan] Induction variable decrement bound analysis.

test/mjsunit/induction-variable-turbofan.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[Jarin, 2016/08/22 07:27:20]

Nit: you can use a shorter copyright. E.g., see test/mjsunit/array-push2.js.

[Franzi, 2016/08/22 09:06:30]

Done.

+
+// Flags: --allow-natives-syntax --turbo
+
+// TurboFan optimizes integer loops. These tests check that we compute
+// the corret upper and lower bounds.

[Jarin, 2016/08/22 07:27:20]

Nit: corret -> correct.

[Franzi, 2016/08/22 09:06:30]

Done.

+function positive_increment() {
+  for (var i = 5; i < 10; i++) {
+    if (i < 0) break;
+    if (i > 20) break;
+    if (i === 7) return true;
+  }
+  return false;
+}
+
+function positive_increment_strict() {
+  for (var i = 5; i < 10; i++) {
+    if (i < 0) break;

[Jarin, 2016/08/22 07:27:20]

Could we change the i < 0 branches to return false? (They should never trigger.)

[Franzi, 2016/08/22 09:06:30]

Done.

+    if (i === 10) return false;
+  }
+  return true;
+}
+
+function positive_increment_non_strict() {
+  for (var i = 5; i <= 10; i++) {
+    if (i < 0) break;
+    if (i === 10) return true;
+  }
+  return false;
+}
+
+function negative_increment() {
+  for (var i = 10; i > 5;) {
+    if (i < 0) break;
+    if (i > 20) break;
+    if (i === 7) return true;
+    i -= 1;
+  }
+  return false;
+}
+
+function positive_decrement() {
+  for (var i = 10; i > 5; i--) {
+    if (i < 0) break;
+    if (i === 7) return true;
+  }
+  return false;
+}
+
+function positive_decrement_strict() {
+  for (var i = 10; i > 5; i--) {
+    if (i < 0) break;
+    if (i === 5) return false;
+  }
+  return true;
+}
+function positive_decrement_non_strict() {
+  for (var i = 10; i >= 5; i--) {
+    if (i < 0) break;
+    if (i === 5) return true;
+  }
+  return false;
+}
+
+function negative_decrement() {
+  for (var i = 5; i < 10;) {
+    if (i < 0) break;
+    if (i === 7) return true;
+    i -= -1;
+  }
+  return false;
+}
+
+function variable_bound() {
+  for (var i = 5; i < 10; i++) {
+    for (var j = 5; j < i; j++) {
+      if (j < 0) break;
+      if (j === 7) return true;
+    }
+  }
+  return false;
+
+}
+
+function test(f) {
+  f();
+  assertTrue(f());
+  %OptimizeFunctionOnNextCall(f);
+  assertTrue(f());
+}
+
+test(positive_increment);
+test(positive_increment_strict);
+test(positive_increment_non_strict);
+test(negative_increment);
+test(positive_decrement);
+test(positive_decrement_strict);
+test(positive_decrement_non_strict);
+test(negative_decrement);
+test(variable_bound);