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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" 

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.


-----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


      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.


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