Bug 121916 – Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

• Status: RESOLVED
• Resolution: WONTFIX
• Component: JavaScriptCore

[Julien Brianceau]

Remove the 2 unused void* parameters from ctiTrampoline function in baseline JIT.

With current implementation in baseline JIT, architectures using 4 argument registers (sh4 and mips for instance) are pushing 2 words on stack for each call to ctiTrampoline: the void* unused2 and the VM* parameters.

[Julien Brianceau]

Created attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

I get 2.5% speed up on my (slow) sh4 platform with this patch, and this patch didn't break anything on my mips platform.

As I don't have ready environments to test this patch properly on all other architectures (ARM, X86 & X86_64), please do not cq+ this patch right now.

[Early Warning System Bot]

Comment on attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

Attachment 212600 [details] did not pass qt-ews (qt):
Output: http://webkit-queues.appspot.com/results/2235171

[Early Warning System Bot]

Comment on attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

Attachment 212600 [details] did not pass qt-wk2-ews (qt-wk2):
Output: http://webkit-queues.appspot.com/results/2219005

[Build Bot]

Comment on attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

Attachment 212600 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.appspot.com/results/2281045

[Build Bot]

Comment on attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

Attachment 212600 [details] did not pass mac-ews (mac):
Output: http://webkit-queues.appspot.com/results/2220004

[Julien Brianceau]

Comment on attachment 212600 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT.

Oops, I forget to update savedRBX offset for X86_64

[Julien Brianceau]

Created attachment 212611 [details]
Get rid of 2 unused parameters from ctiTrampoline function in baseline JIT (2nd try)

Should be better

[Filip Pizlo]

I think those are reserved for DFG-style native calls. msaboff and I are about to make the baseline JIT use that calling convention also. So not only is this likely to break the DFG but it will get rolled out once we fix the baseline JIT. 

Or are you sure that arguments to functions that take more than 4 parameters are passed through some other set of slots?

[Julien Brianceau]

(In reply to comment #8)
> I think those are reserved for DFG-style native calls. msaboff and I are about to make the baseline JIT use that calling convention also. So not only is this likely to break the DFG but it will get rolled out once we fix the baseline JIT. 

Ok it'd better to wait your change in baseline JIT then.

[Julien Brianceau]

Closing bug, this change is no more relevant since r158751 (https://bugs.webkit.org/show_bug.cgi?id=123844)