Improve array to string conversion.

test/mjsunit/string-natives.js

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-// Flags: --allow-natives-syntax
+// Flags: --expose-gc --allow-natives-syntax
 
-// The original problem from the bug: In the example below SMI check for b
-// generated for inlining of equals invocation (marked with (*)) will be hoisted
-// out of the loop across the typeof b === "object" condition and cause an
-// immediate deopt. Another problem here is that no matter how many time we
-// deopt and reopt we will continue to produce the wrong code.
-//
-// The fix is to notice when a deopt and subsequent reopt doesn't find
-// additional type information, indicating that optimistic LICM should be
-// disabled during compilation.
+function test() {
+  var s1 = %NewString(26, true);
+  for (i = 0; i < 26; i++) %_OneByteSeqStringSetChar(s1, i, i+65);
+  assertEquals("ABCDEFGHIJKLMNOPQRSTUVWXYZ", s1);
+  %TruncateString(s1, 13);
+  assertEquals("ABCDEFGHIJKLM", s1);
+  assertThrows(function() { %TruncateString(s1, 14) });
+  assertThrows(function() { %TruncateString(s1, 0) });
 
-function eq(a, b) {
-  if (typeof b === "object") {
-    return b.equals(a);  // (*)
+  var s2 = %NewString(26, false);
+  for (i = 0; i < 26; i++) %_TwoByteSeqStringSetChar(s2, i, i+65);
+  assertEquals("ABCDEFGHIJKLMNOPQRSTUVWXYZ", s2);
+  %TruncateString(s2, 13);
+  assertEquals("ABCDEFGHIJKLM", s2);
+
+  var s3 = %NewString(26, false);
+  for (i = 0; i < 26; i++) %_TwoByteSeqStringSetChar(s3, i, i+1000);
+  for (i = 0; i < 26; i++) assertEquals(s3[i], String.fromCharCode(i+1000));
+
+  var a = [];
+  for (var i = 0; i < 1000; i++) {
+    var s = %NewString(10000, i % 2 == 1);
+    a.push(s);
   }
-  return a === b;
+
+  gc();
+
+  for (var i = 0; i < 1000; i++) {
+    assertEquals(10000, a[i].length);
+    %TruncateString(a[i], 5000);
+  }
+
+  gc();
+
+  for (var i = 0; i < 1000; i++) {
+    assertEquals(5000, a[i].length);
+  }
 }
 
-Object.prototype.equals = function (other) {
-  return (this === other);
-};
 
-function test() {
-  for (var i = 0; !eq(i, 10); i++)
-    ;
-}
-
-eq({}, {});
-eq({}, {});
-eq(1, 1);
-eq(1, 1);
+test();
 test();
 %OptimizeFunctionOnNextCall(test);
 test();
-%OptimizeFunctionOnNextCall(test);
-// Second compilation should have noticed that LICM wasn't a good idea, and now
-// function should no longer deopt when called.
-test();
-assertTrue(2 != %GetOptimizationStatus(test));