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Re: nightmares with biased stack pointers
- To: davem at jenolan dot rutgers dot edu (David S. Miller)
- Subject: Re: nightmares with biased stack pointers
- From: Richard Henderson <rth at cygnus dot com>
- Date: Sat, 13 Sep 1997 10:11:11 -0700 (PDT)
- Cc: egcs at cygnus dot com
- Reply-To: rth at cygnus dot com (Richard Henderson)
> 3) Hey look, taking into account the known alignment of the stack
> frame and the "add sp, const, reg; srlx 4; sllx 4;" sequence,
> I can determine that this is really an alignment of the 'constant'
> so I can merge this into a constant operation and blow the two
> shifts away.
I presume you tried subtracting out the bias before applying the
const alignment logic? I don't know where you found the code that
was doing this so I don't know what else it would impact.
Failing that, I suppose you could try to use elimination from a
"soft" stack pointer to the hard stack pointer. I don't know
how many places would then have to be taught to treat manipulations
of HARD_STACK_POINTER_REGNUM specially like they sometimes do
for the current stack pointer.
r~