160925 2016-08-16 17:31:27 -0700 Remove invalid assertion in the DFG backend's GetById emitter. 2016-08-17 14:03:00 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Local Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 mark.lam mark.lam benjamin fpizlo ggaren keith_miller msaboff saam webkit-bug-importer oldest_to_newest 1220683 0 mark.lam 2016-08-16 17:31:27 -0700 The DFG bytecode parser will force an OSR exit if it sees an op_get_by_id or op_get_by_val with a SpecNone prediction. Hence, it is safe to emit code for the GetById node even if its prediction is SpecNone. The GetById node may still be seen by the DFG backend, but it is valid for it to have a SpecNone prediction. 1220686 1 mark.lam 2016-08-16 17:33:15 -0700 <rdar://problem/27248961> 1220689 2 mark.lam 2016-08-16 17:43:43 -0700 (In reply to comment #0) > The DFG bytecode parser will force an OSR exit if it sees an op_get_by_id or > op_get_by_val with a SpecNone prediction. Hence, it is safe to emit code > for the GetById node even if its prediction is SpecNone. The GetById node > may still be seen by the DFG backend, but it is valid for it to have a > SpecNone prediction. This may not be true. In my test locally, I'm seeing the assertion without a ForceOSRExit node preceding the GetById node. I'll investigate further. 1220928 3 mark.lam 2016-08-17 12:45:06 -0700 My initial read of the code was wrong and misleading. The GetById assertion that the node's prediction not be SpecNone in the DFG backend is just plain wrong. It assumes that we can never have a GetById node without a type prediction, but that is not true. The following test case proves otherwise: function foo() { "use strict"; return --arguments["callee"]; } Will remove the assertion. Nothing else needs to change as the DFG is working correctly without the assertion. 1220950 4 286325 mark.lam 2016-08-17 13:52:13 -0700 Created attachment 286325 proposed patch. 1220954 5 mark.lam 2016-08-17 14:03:00 -0700 Thanks for the review. Landed in r204570: <http://trac.webkit.org/r204570>. 286325 2016-08-17 13:52:13 -0700 2016-08-17 13:55:19 -0700 proposed patch. bug-160925.patch text/plain 3621 mark.lam SW5kZXg6IEpTVGVzdHMvQ2hhbmdlTG9nCj09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIEpTVGVzdHMvQ2hhbmdlTG9n CShyZXZpc2lvbiAyMDQ1NjkpCisrKyBKU1Rlc3RzL0NoYW5nZUxvZwkod29ya2luZyBjb3B5KQpA QCAtMSwzICsxLDEzIEBACisyMDE2LTA4LTE3ICBNYXJrIExhbSAgPG1hcmsubGFtQGFwcGxlLmNv bT4KKworICAgICAgICBSZW1vdmUgYW4gaW52YWxpZCBhc3NlcnRpb24gaW4gdGhlIERGRyBiYWNr ZW5kJ3MgR2V0QnlJZCBlbWl0dGVyLgorICAgICAgICBodHRwczovL2J1Z3Mud2Via2l0Lm9yZy9z aG93X2J1Zy5jZ2k/aWQ9MTYwOTI1CisgICAgICAgIDxyZGFyOi8vcHJvYmxlbS8yNzI0ODk2MT4K KworICAgICAgICBSZXZpZXdlZCBieSBOT0JPRFkgKE9PUFMhKS4KKworICAgICAgICAqIHN0cmVz cy9kZmctZ2V0LWJ5LWlkLXNob3VsZC1ub3QtYXNzZXJ0LW5vbi1udWxsLXByZWRpY3Rpb24uanM6 IEFkZGVkLgorCiAyMDE2LTA4LTE2ICBSeWFuIEhhZGRhZCAgPHJ5YW5oYWRkYWRAYXBwbGUuY29t 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