[regexp] Avoid unneeded accesses to lastIndex

test/mjsunit/regress/regress-2437.js

 // Copyright 2012 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.
 
 // Summary of the spec: lastIndex is reset to 0 if
-// - a regexp fails to match, regardless of global or non-global.
+// - a global or sticky regexp fails to match.
 // - a global regexp is used in a function that returns multiple results,
 //   such as String.prototype.replace or String.prototype.match, since it
 //   repeats the regexp until it fails to match.
 // Otherwise lastIndex is only set when a global regexp matches, to the index
 // after the match.
 
 // Test Regexp.prototype.exec
 r = /a/;
 r.lastIndex = 1;
 r.exec("zzzz");
-assertEquals(0, r.lastIndex);
+assertEquals(1, r.lastIndex);
 
 // Test Regexp.prototype.test
 r = /a/;
 r.lastIndex = 1;
 r.test("zzzz");
-assertEquals(0, r.lastIndex);
+assertEquals(1, r.lastIndex);
 
 // Test String.prototype.match
 r = /a/;
 r.lastIndex = 1;
 "zzzz".match(r);
-assertEquals(0, r.lastIndex);
+assertEquals(1, r.lastIndex);
 
 // Test String.prototype.replace with atomic regexp and empty string.
 r = /a/;
 r.lastIndex = 1;
 "zzzz".replace(r, "");
 assertEquals(0, r.lastIndex);
 
 // Test String.prototype.replace with non-atomic regexp and empty string.
 r = /\d/;
 r.lastIndex = 1;
@@ skipping 46 matching lines @@
 r.lastIndex = -1;
 "01234567".replace(r, "x");
 assertEquals(0, r.lastIndex);
 
 r.lastIndex = -1;
 "0123abcd".match(r);
 assertEquals(-1, r.lastIndex);
 
 r.lastIndex = -1;
 "01234567".match(r);
-assertEquals(0, r.lastIndex);
+assertEquals(-1, r.lastIndex);
 
 // Also test RegExp.prototype.exec and RegExp.prototype.test
 r = /a/g;
 r.lastIndex = 1;
 r.exec("01234567");
 assertEquals(0, r.lastIndex);
 
 r.lastIndex = 1;
 r.exec("0123abcd");
 assertEquals(5, r.lastIndex);
 
 r = /a/;
 r.lastIndex = 1;
 r.exec("01234567");
-assertEquals(0, r.lastIndex);
+assertEquals(1, r.lastIndex);
 
 r.lastIndex = 1;
 r.exec("0123abcd");
 assertEquals(1, r.lastIndex);
 
 r = /a/g;
 r.lastIndex = 1;
 r.test("01234567");
 assertEquals(0, r.lastIndex);
 
 r.lastIndex = 1;
 r.test("0123abcd");
 assertEquals(5, r.lastIndex);
 
 r = /a/;
 r.lastIndex = 1;
 r.test("01234567");
-assertEquals(0, r.lastIndex);
+assertEquals(1, r.lastIndex);
 
 r.lastIndex = 1;
 r.test("0123abcd");
 assertEquals(1, r.lastIndex);