[turbofan] Induction variable decrement bound analysis.

test/mjsunit/induction-variable-turbofan.js

+// Copyright 2016 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 --turbo
+
+// TurboFan optimizes integer loops. These tests check that we compute
+// the correct upper and lower bounds.
+function positive_increment() {
+  for (var i = 5; i < 10; i++) {
+    if (i < 0) return false;
+    if (i > 20) return false;
+    if (i === 7) return true;
+  }
+  return false;
+}
+
+function positive_increment_strict() {
+  for (var i = 5; i < 10; i++) {
+    if (i < 0) return false;
+    if (i === 10) return false;
+  }
+  return true;
+}
+
+function positive_increment_non_strict() {
+  for (var i = 5; i <= 10; i++) {
+    if (i < 0) return false;
+    if (i === 10) return true;
+  }
+  return false;
+}
+
+function negative_increment() {
+  for (var i = 10; i > 5;) {
+    if (i < 0) return false;
+    if (i > 20) return false;
+    if (i === 7) return true;
+    i -= 1;
+  }
+  return false;
+}
+
+function positive_decrement() {
+  for (var i = 10; i > 5; i--) {
+    if (i < 0) return false;
+    if (i === 7) return true;
+  }
+  return false;
+}
+
+function positive_decrement_strict() {
+  for (var i = 10; i > 5; i--) {
+    if (i < 0) return false;
+    if (i === 5) return false;
+  }
+  return true;
+}
+function positive_decrement_non_strict() {
+  for (var i = 10; i >= 5; i--) {
+    if (i < 0) return false;
+    if (i === 5) return true;
+  }
+  return false;
+}
+
+function negative_decrement() {
+  for (var i = 5; i < 10;) {
+    if (i < 0) return false;
+    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) return false;
+      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);