[LLVMdev] x86-64 large stack offsets

Jakob Stoklund Olesen stoklund at 2pi.dk
Tue Sep 27 09:10:34 PDT 2011

On Sep 27, 2011, at 1:04 AM, Duncan Sands wrote:

> Hi Jakob,
>> The fundamental problem is that currently nothing in the x86 target depends on correct liveness after register allocation. Since many post-RA passes modify the code, there is a good chance they will update liveness incorrectly, or not at all in some cases.
>> Your patches to clean this up will be welcome, but please make x86's using the register scavenger enabled by a command line flag. The majority of x86 users don't want to pay the (small) compile time cost and risk of assertions.
> wouldn't adding a command line flag just make this feature less tested and
> more unreliable?  It hardly seems worth adding it if it is so unreliable
> that it typically has to be turned off.

If Cameron and David can clean things up so it is stable, we can consider turning it on by default.  If not, we can remove it again.

I don't know how big the problem is. The trickle of scavenger assertions from ARM has slowed down.


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