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AW: [avr-gcc-list] Register Usage


From: Haase Bjoern (PT-BEU/EMT) *
Subject: AW: [avr-gcc-list] Register Usage
Date: Thu, 20 Oct 2005 12:57:38 +0200

It is very likely that you will get reload failures because gcc sometimes needs 
three pointer registers, but you could try to use the -ffixed option for 
marking X to be a "fixed" register. The failure would show up at compile time 
when gcc complains that there are not enough registers in class "pointer regs" 
available.

IIRC also the boot sequence will still use the X register. Also eeprom support 
in avr-libc will no longer work.

Only safe register to be marked as "fixed" is r2 ... r7, IIRC.

Bjoern.

-----Urspr√ľngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von Ram Kumar Rengaswamy
Gesendet: Donnerstag, 20. Oktober 2005 10:51
An: address@hidden
Betreff: [avr-gcc-list] Register Usage

Hi,

      I am interested in compiling a C code for ATMega128 such that  
it never uses the register pair X (R27:R26). Could someone direct me  
as to how I could go about doing it with avr-gcc.

Thanks,
-Ram


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