[Vm-dev] Re: [squeak-dev] New Cog VMs available

[Douglas McPherson]

ARMv6 binaries updated accordingly.

On Dec 6, 2014, at 19:17 , Eliot Miranda wrote:

> Oops, for http://www.mirandabanda.org/files/Cog/VM/VM.r3163/ read http://www.mirandabanda.org/files/Cog/VM/VM.r3164
> 
> On Sat, Dec 6, 2014 at 1:53 PM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> ... at http://www.mirandabanda.org/files/Cog/VM/VM.r3163/.
> 
> CogVM binaries as per VMMaker.oscog-eem.972/r3163
> 
> Fix a devilishly tricky bug with 32-bit Spur and PICs in the Cogit.  In 32-bit
> Spur only zero is a valid cache tag, that for Characters, due to SmallIntegers
> having both 2r11 and 2r01 as valid tags.  The cache check prolog collapses
> these down onto 1 by anding with 1 and hence collapses Character's 2r10 to 0.
> 
> The cache tag is also tested in the PIC abort routine to distinguish between
> an MNU abort and an interpret abort.  A PIC MNU entry jumps to code that first
> zeros the cache tag (held in ClassReg) before calling the abort routine, which
> tests ClassReg and selects the relevant abort processing.
> 
> Hence in 32-bit Spur if a send site is linked for Character and later extended
> to a PIC with an interpret case, that interpret case will instead invoke MNU
> processing.  This is rare; first there needs to be a send to a CHaracter, then
> a send to something else which binds to something that must be interpreted.
> Ouch.
> 
> The fix is simple; if a send site that was linked with a zero cache tag (which
> can only happen in 32-bit Spur) link to an open PIC instead of to a closed PIC,
> or in the case of an MNU do not link.
> 
> Add a debug lookup routine that only looks up (and follows forwarding pointers).
> 
> Add a -breakmnu vm argument that calls warning on an mnu of a specific selector.
> 
> Fix SmartSyntaxPlugin code generation for Spur of
> 
> - asOop: old code assumed 4 byte oops & headers
> - Unsigned old code assumed 32-bit oops
> 
> 
> Affects AsyncFilePlugin, BochsIA32Plugin & FT2Plgin.
> 
> Avoid duplication of effort in special selector send forwarding fault handling.
> 
> Improve stack trace printing for Newspeak and Glue by providing something that
> assumes the penultimate literal is the selector or an AdditionalMethodState-like
> thing containing it.
> 
> Reimplement primitiveCopyObject to work for both pointer and bits objects.
> This to support a good Object>>clone for Spur.
> 
> Fix Spur's isWordsOrBytes[NonImm]:.  Old code answered true for CompiledMethods.
> -- 
> best,
> Eliot
> 
> 
> 
> -- 
> best,
> Eliot
> 

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