Promote and inflate string slices during scavenging GC.

test/mjsunit/string-slices.js

 // Copyright 2008 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 // 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.
 
-// Flags: --string-slices --expose-externalize-string
+// Flags: --string-slices --expose-externalize-string --expose-gc
 
 var s = 'abcdefghijklmn';
 assertEquals(s, s.substr());
 assertEquals(s, s.substr(0));
 assertEquals(s, s.substr('0'));
 assertEquals(s, s.substr(void 0));
 assertEquals(s, s.substr(null));
 assertEquals(s, s.substr(false));
 assertEquals(s, s.substr(0.9));
 assertEquals(s, s.substr({ valueOf: function() { return 0; } }));
@@ skipping 67 matching lines @@
 x += x;
 x += x;
 x += x;  // 2^10
 x += x;
 x += x;
 var xl = x.length;
 var cache = [];
 for (var i = 0; i < 1000; i++) {
   var z = x.substring(i % xl);
   assertEquals(xl - (i % xl), z.length);
-  cache.push(z);
 }
 
 
 // Same with two-byte strings
 var x = "\u2028123456789ABCDEF";
 x += x;  // 2^5
 x += x;
 x += x;
 x += x;
 x += x;
 x += x;  // 2^10
 x += x;
 x += x;
+x += x;
+x += x;
+x += x;
+x += x;
+x += x;
 var xl = x.length;
 var cache = [];
 for (var i = 0; i < 1000; i++) {
   var z = x.substring(i % xl);
   assertEquals(xl - (i % xl), z.length);
-  cache.push(z);
 }
 
 // Substring of substring.
 var cache = [];
 var last = x;
-var offset = 0;
-for (var i = 0; i < 64; i++) {
-  var z = last.substring(i);
+for (var i = 0; i < 100000; i++) {
+  var z = last.substring(1);
   last = z;
   cache.push(z);
-  offset += i;
 }
-for (var i = 63; i >= 0; i--) {
+
+// Fill up new space with junk and then invoke GC.
+var fill = [];
+for (var i = 0; i < 1000000; i++) {
+  fill.push(i + " ");
+}
+gc(true);
+
+for (var i = 100000; i > 0; i--) {
   var z = cache.pop();
   assertTrue(/\u2028123456789ABCDEF/.test(z));
-  assertEquals(xl - offset, z.length);
-  assertEquals(x.charAt(i*(i+1)/2), z.charAt(0));
-  offset -= i;
+  assertEquals(xl - i, z.length);
+  assertEquals(x.charAt(i), z.charAt(0));
 }
 
 // Test charAt for different strings.
 function f(s1, s2, s3, i) {
   assertEquals(String.fromCharCode(97+i%11), s1.charAt(i%11));
   assertEquals(String.fromCharCode(97+i%11), s2.charAt(i%11));
   assertEquals(String.fromCharCode(98+i%11), s3.charAt(i%11));
   assertEquals(String.fromCharCode(101), s3.charAt(3));
 }
 
@@ skipping 26 matching lines @@
     utf.substring(5,1) + utf.substring(3,7));
 
 /*
 // Externalizing strings.
 var a = "123456789qwertyuiopasdfghjklzxcvbnm";
 var b = a.slice(1,-1);
 assertEquals(a.slice(1,-1), b);
 externalizeString(a);
 assertEquals(a.slice(1,-1), b);
 */