480237 - TM: Use branching instead of logic expression when unboxing numbers

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[Andreas Gal :gal]

This generates better code. Small speedup on SS.

Old:

mov eax,0(eax+ebx*4)            
mov edx,eax                     
and edx,7                       
cmp edx,2                       
sete edx                        
movzx edx,edx                   
and eax,1                       
or eax,edx                      
test eax,eax
je 0x2a8fdc

New:

mov eax,0(eax+ebx*4)           
mov edx,eax              
and edx,1                 
cmp edx,1                  
je 0x264fcc               
and eax,7                  
cmp eax,2                 
jne 0x2a8fdc

Comment 1

[Andreas Gal :gal]

Attachment: patch

Comment 2

[Robert Sayre]

this needs to be rebased

Comment 3

[Nochum Sossonko [:Natch]]

These bugs are all part of a search I made for js bugs that are getting lost in transit:

http://tinyurl.com/jsDeadEndBugs

They all have a review+'ed, non-obsoleted patch and are not marked fixed-in-tracemonkey or checkin-needed but have not seen any activity in 300 days. Some of these got lost simply because the assignee/patch provider never requested a checkin, or just because they were forgotten about.

Comment 4

[Nicholas Nethercote [inactive]]

This bug is moot, thanks to fatvals, for which unboxing a number is much faster.