1263543 - SpiderMonkey cannot work on 64 bits AIX

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine, defect)

Description

[Matthieu S]

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0
Build ID: 20160304114926

Steps to reproduce:

Build MongoDB 3.2 (including SpiderMonkey 38) on 64 bits AIX.


Actual results:

Lots of crashes in MongoDB JavaScript tests


Expected results:

No crashes

Comment 1

[Matthieu S]

The issue is related to the punboxing.
Using 47 bits pointer and 17 bits tags only works if all the pointer have 17 non-significant bits.

But on AIX, mmap returns pointers in the 0x07000000_00000000-0x07FFFFFF_FFFFFFFF range (see : https://www.ibm.com/support/knowledgecenter/ssw_aix_72/com.ibm.aix.genprogc/understanding_mem_mapping.htm ), which means there are only 6 non-significant bits.

This is compromising the port to AIX for all projects using SpiderMonkey.

Comment 2

[Nicolas B. Pierron [:nbp | PTO until 11/11]]

See also Bug 1250400.

Comment 3

[kademorton]

As stated above this may be a  duplicate of Bug 1250400 https://bugzilla.mozilla.org/show_bug.cgi?id=1250400 which may in turn be a duplicate of Bug 1143022 https://bugzilla.mozilla.org/show_bug.cgi?id=1143022 but unsure.

Comment 4

[Matthieu S]

Yes, looks like the same issue. The choice of 47 bits pointer seems to be closely linked to AMD64 limitations (virtual addresses limited to 48 significant bits), so it could be an issue with any other 64 bits architecture allowing more than 47 significant bits, not just IBM Power or ARM.

It might also becomes an issue with x86-64 if the significant part is extended in future implementations (but this won't probably come soon).