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AW: [avr-gcc-list] SIGNAL and INTERRUPT overhead

From: Haase Bjoern (PT-BEU/EMT) *
Subject: AW: [avr-gcc-list] SIGNAL and INTERRUPT overhead
Date: Tue, 23 Aug 2005 11:48:31 +0200

Benjamin Titzer wrote:

>Sounds to me like the design of GCC and the constraints of a particular
>calling convention do not allow it to do something smart here. I think the
>solution that would satisfy most everyone involved would be for the
>compiler to generate code that only saves the state of registers that it
>uses (and overwrites) and then restore them upon exit. This is a simple
>use-def analysis on the registers and would be simple enough to implement.

FYI, I am working on a scheme that GCC remembers for all of the functions that 
it has already compiled which registers are actually clobbered so that all 
other functions do not need to safe/restore the registers that are preserved by 
the respective function. This could then be used also by the 
prologues/epilogues for the SIGNAL/INTERRUPT functions to improve efficiency.

This will be, however, a rather tough work, don't expect too much during the 
next week.



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