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Re: Reload Issue -- I can't believe we haven't hit this before


On Tue, 2005-04-19 at 08:49 +0200, Eric Botcazou wrote:
> > So the combination of the TCB merge plus the pending jump threading
> > changes apparently has ticked a reload bug which manifests itself with
> > the stage1 compiler mis-compiling the stage2 compiler.
> >
> > [...]
> >
> > Which faults because the memory location is actually  read-only memory.
> 
> PR rtl-optimization/15248.
Ah.  Good.  I was having a bloody hard time believing we hadn't run into
this before.

> 
> > What's not clear to me is how best to fix this.
> >
> > We could try to delete all assignments to pseudos which are equivalent
> > to MEMs.
> >
> > We could avoid recording equivalences when the pseudo is set more than
> > once.
> >
> > Other possibilities?
> 
> For 3.3 and 3.4, this was "fixed" by not recording memory equivalences that 
> have the infamous RTX_UNCHANGING_P flag set.
Also a possibility.  Making the equivalent change (!MEM_READONLY_P)
appears to do the trick for mainline.

Jeff


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