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

[Haase Bjoern (PT-BEU/EMT) *]

Citing from the gcc documentation:

"Compiling multiple files at once to a single output file in _unit-at-a-time_ 
mode allows the compiler to use information gained from all of the files when 
compiling each of them."

-O2 and -Os switch on -funit-at-a-time.

Yours,

Björn

-----Ursprüngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von David Brown
Gesendet: Mittwoch, 24. August 2005 10:26
An: address@hidden
Betreff: Re: [avr-gcc-list] SIGNAL and INTERRUPT overhead


----- Original Message -----
From: "Haase Bjoern (PT-BEU/EMT) *" <address@hidden>

>Benjamin Titzer wrote:

>>That's a big problem with the usual way of building code, with functions
>>or set of related functions in
>>different files. When the compiler groks the files, it does not have all
>>the information that would help
>>it build a much better optimized code.

>IIUC, it would be sufficient to compile them at the same time. I.e. use gcc
file1.c file2.c -o >app.elf ...


Does compiling multiple C files at once have other benifits?  And do you
have to link them at the same time?  I have always thought that a line such
as "gcc file1.c file2.c -o app.elf" is equivilent to seperately compiling
each C file, and then linking them as a seperate pass - hence the
traditional makefile to re-compile modules to object files as necessary.

Regards,

David




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