83234 2012-04-04 16:31:50 -0700 DFG InstanceOf should not uselessly speculate cell 2012-04-04 17:59:24 -0700 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) All All RESOLVED FIXED P2 Normal --- 1 fpizlo webkit-unassigned oldest_to_newest 596083 0 fpizlo 2012-04-04 16:31:50 -0700 A useless speculation is one that: 1) Is performed on a value that dies at the point of speculation. 2) Handling the case where the speculation would fail is trivial and takes fewer instructions than an OSR exit trampoline (i.e. <12 bytes on x86). InstanceOf has a SpeculateCell optimization, which is probably great most of the time, but there are times when you do something like: if (o.f instanceof p) The temporary result of o.f dies immediately. Handling the case where it's not a cell is super easy: just return false. So there's little use in speculating cell here. 596087 1 135717 fpizlo 2012-04-04 16:34:55 -0700 Created attachment 135717 the patch 596153 2 fpizlo 2012-04-04 17:59:24 -0700 Landed in http://trac.webkit.org/changeset/113269 135717 2012-04-04 16:34:55 -0700 2012-04-04 16:37:30 -0700 the patch dontspeccell_patch_1.diff text/plain 1848 fpizlo SW5kZXg6IFNvdXJjZS9KYXZhU2NyaXB0Q29yZS9DaGFuZ2VMb2cKPT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQotLS0gU291 cmNlL0phdmFTY3JpcHRDb3JlL0NoYW5nZUxvZwkocmV2aXNpb24gMTEzMjYxKQorKysgU291cmNl L0phdmFTY3JpcHRDb3JlL0NoYW5nZUxvZwkod29ya2luZyBjb3B5KQpAQCAtMSwzICsxLDE2IEBA CisyMDEyLTA0LTA0ICBGaWxpcCBQaXpsbyAgPGZwaXpsb0BhcHBsZS5jb20+CisKKyAgICAgICAg REZHIEluc3RhbmNlT2Ygc2hvdWxkIG5vdCB1c2VsZXNzbHkgc3BlY3VsYXRlIGNlbGwKKyAgICAg ICAgaHR0cHM6Ly9idWdzLndlYmtpdC5vcmcvc2hvd19idWcuY2dpP2lkPTgzMjM0CisKKyAgICAg ICAgUmV2aWV3ZWQgYnkgTk9CT0RZIChPT1BTISkuCisgICAgICAgIAorICAgICAgICBJZiBJbnN0 YW5jZU9mIGlzIHRoZSBvbmx5IHVzZXIgb2YgaXRzIGNoaWxkIHRoZW4gZG9uJ3Qgc3BlY3VsYXRl IGNlbGwsIHNpbmNlCisgICAgICAgIHRoZSBub3QtY2VsbCBjYXNlIGlzIHN1cGVyIGVhc3kgdG8g aGFuZGxlLgorCisgICAgICAgICogZGZnL0RGR1NwZWN1bGF0aXZlSklULmNwcDoKKyAgICAgICAg KEpTQzo6REZHOjpTcGVjdWxhdGl2ZUpJVDo6Y29tcGlsZUluc3RhbmNlT2YpOgorCiAyMDEyLTA0 LTA0ICBNaWNoYWVsIFNhYm9mZiAgPG1zYWJvZmZAYXBwbGUuY29tPgogCiAgICAgICAgIENvbnN0 YW50IEJsaW5kaW5nIGZvciBhZGQvc3ViIGltbWVkaWF0ZSBjcmFzaGVzIGluIEFybVY3IHdoZW4g ZGVzdCBpcyBTUApJbmRleDogU291cmNlL0phdmFTY3JpcHRDb3JlL2RmZy9ERkdTcGVjdWxhdGl2 ZUpJVC5jcHAKPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PQotLS0gU291cmNlL0phdmFTY3JpcHRDb3JlL2RmZy9ERkdTcGVj dWxhdGl2ZUpJVC5jcHAJKHJldmlzaW9uIDExMzI0MykKKysrIFNvdXJjZS9KYXZhU2NyaXB0Q29y ZS9kZmcvREZHU3BlY3VsYXRpdmVKSVQuY3BwCSh3b3JraW5nIGNvcHkpCkBAIC0yMjI5LDggKzIy MjksMTIgQEAgdm9pZCBTcGVjdWxhdGl2ZUpJVDo6Y29tcGlsZUluc3RhbmNlT2ZGbwogCiB2b2lk IFNwZWN1bGF0aXZlSklUOjpjb21waWxlSW5zdGFuY2VPZihOb2RlJiBub2RlKQogewotICAgIGlm ICghIShhdChub2RlLmNoaWxkMSgpKS5wcmVkaWN0aW9uKCkgJiB+UHJlZGljdENlbGwpICYmICEh KG1fc3RhdGUuZm9yTm9kZShub2RlLmNoaWxkMSgpKS5tX3R5cGUgJiB+UHJlZGljdENlbGwpKSB7 CisgICAgaWYgKCghIShhdChub2RlLmNoaWxkMSgpKS5wcmVkaWN0aW9uKCkgJiB+UHJlZGljdENl bGwpCisgICAgICAgICAmJiAhIShtX3N0YXRlLmZvck5vZGUobm9kZS5jaGlsZDEoKSkubV90eXBl ICYgflByZWRpY3RDZWxsKSkKKyAgICAgICAgfHwgYXQobm9kZS5jaGlsZDEoKSkuYWRqdXN0ZWRS ZWZDb3VudCgpID09IDEpIHsKICAgICAgICAgLy8gSXQgbWlnaHQgbm90IGJlIGEgY2VsbC4gU3Bl Y3VsYXRlIGxlc3MgYWdncmVzc2l2ZWx5LgorICAgICAgICAvLyBPcjogaXQgbWlnaHQgb25seSBi ZSB1c2VkIG9uY2UgKGkuZS4gYnkgdXMpLCBzbyB3ZSBnZXQgemVybyBiZW5lZml0CisgICAgICAg IC8vIGZyb20gc3BlY3VsYXRpbmcgYW55IG1vcmUgYWdncmVzc2l2ZWx5IHRoYW4gd2UgYWJzb2x1 dGVseSBuZWVkIHRvLgogICAgICAgICAKICAgICAgICAgSlNWYWx1ZU9wZXJhbmQgdmFsdWUodGhp cywgbm9kZS5jaGlsZDEoKSk7CiAgICAgICAgIFNwZWN1bGF0ZUNlbGxPcGVyYW5kIHByb3RvdHlw ZSh0aGlzLCBub2RlLmNoaWxkMygpKTsK