Simple support for const variables in Crankshaft....

test/mjsunit/compiler/regress-const.js

+// Copyright 2011 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
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+//       with the distribution.
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+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
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+// "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,
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+// 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.
+
+// Test const initialization and assignments.
+function f() {
+  var x = 42;
+  while (true) {
+    const y = x;
+    if (--x == 0) return y;
+  }
+}
+
+function g() {
+  const x = 42;
+  x += 1;
+  return x;
+}
+
+for (var i = 0; i < 1000000; i++) {
+  f();
+  g();
+}
+
+assertEquals(42, f());
+assertEquals(42, g());
+
+
+function h(a, b) {
+  var r = a + b;
+  const X = 42;
+  return r + X;
+}
+
+for (var i=0; i<10000000; i++) f(1,2);
+assertEquals(45, h(1,2));
+assertEquals("foo742", h("foo", 7));