[LLVMdev] JIT memory manager: NeedsExactSize() ?

nicolas geoffray nicolas.geoffray at gmail.com
Thu Jul 22 04:36:48 PDT 2010


Thanks Chris for the heads up.

No vmkit does not use that feature anymore, but I have seen some commits on
other architectures that may imply that external users are using it.

Nicolas

On Thu, Jul 22, 2010 at 2:25 AM, Chris Lattner <clattner at apple.com> wrote:

>
> On Jul 21, 2010, at 5:01 PM, Reid Kleckner wrote:
>
> > Oh god, rip it out.  IIRC it's just a complete parallel
> > reimplementation of bunch of instruction encoding stuff just to
> > compute the code size.
>
> Yeah, I know.  It's the 3rd and most incorrect copy of the instruction
> emitter.  I really really want to rip it out, but we do have a unit test for
> the 'needsexactsize()' stuff, so I figure someone might actually care.  Does
> vmkit use this?
>
> -Chris
>
>
> >
> > Reid
> >
> > On Wed, Jul 21, 2010 at 3:52 PM, Chris Lattner <clattner at apple.com>
> wrote:
> >> The JIT has a codepath that supports JIT memory managers that return
> true for NeedsExactSize().  This is particularly bad for X86, because the
> "exact size" is not exact, and looks completely wrong in a lot of cases.  Is
> anyone using this?  Can I rip it out?  This stuff should go away with the
> mc'ization of the JIT in the long term.
> >>
> >> -Chris
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>
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