Bug 126543

Summary: FTL should ascribe range meta-data when loading array.length
Product: WebKit Reporter: Filip Pizlo <fpizlo>
Component: JavaScriptCoreAssignee: Filip Pizlo <fpizlo>
Status: RESOLVED FIXED    
Severity: Normal CC: atrick, barraclough, ggaren, mark.lam, mhahnenberg, msaboff, nrotem, oliver, sam
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: All   
OS: All   
Bug Depends on:    
Bug Blocks: 112840    
Attachments:
Description Flags
the patch ggaren: review+

Filip Pizlo
Reported 2014-01-06 15:41:01 PST
This will allow some interesting optimizations on the LLVM side.
Attachments
the patch (19.42 KB, patch)
2014-01-19 17:20 PST, Filip Pizlo 		ggaren: review+
DetailsFormatted DiffDiff
View All Add attachment proposed patch, testcase, etc.
Filip Pizlo
Comment 1 2014-01-19 17:20:46 PST
Created attachment 221604 [details] the patch
Filip Pizlo
Comment 2 2014-01-19 17:22:34 PST
Landed in branch in http://trac.webkit.org/changeset/162299
Geoffrey Garen
Comment 3 2014-01-19 17:59:37 PST
Comment on attachment 221604 [details] the patch View in context: https://bugs.webkit.org/attachment.cgi?id=221604&action=review r=me > Source/JavaScriptCore/ftl/FTLCommonValues.cpp:65 > + , nonNegativeInt32(constInt(int32, 0, SignExtend), constInt(int32, 1ll << 31, SignExtend)) Why the "ll" after the "1"?
Filip Pizlo
Comment 4 2014-01-19 18:12:23 PST
(In reply to comment #3) > (From update of attachment 221604 [details]) > View in context: https://bugs.webkit.org/attachment.cgi?id=221604&action=review > > r=me > > > Source/JavaScriptCore/ftl/FTLCommonValues.cpp:65 > > + , nonNegativeInt32(constInt(int32, 0, SignExtend), constInt(int32, 1ll << 31, SignExtend)) > > Why the "ll" after the "1"? constInt() takes a long long, so I figured that I'd avoid all ambiguity in the implicit integer casting by just starting out with 1 being a long long. Also, "1" is a 32-bit int and 2^31 isn't a valid 32-bit int value. So, 1 << 31 is subject to some overflow rules, and I don't feel like figuring out what exactly they are. It's one of those things that feels like it might fall under undefined behavior and I don't like having to think about that.
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