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

From: David Brown
Subject: Re: [avr-gcc-list] SIGNAL and INTERRUPT overhead
Date: Wed, 24 Aug 2005 13:29:55 +0200

Ah, I see that is a new feature of gcc 3.4 - whose manual I haven't read as
thoroughly as older versions.  I guess it's time to change my makefiles!



----- Original Message -----
From: "Haase Bjoern (PT-BEU/EMT) *" <address@hidden>
To: "David Brown" <address@hidden>; <address@hidden>
Sent: Wednesday, August 24, 2005 11:39 AM
Subject: AW: [avr-gcc-list] SIGNAL and INTERRUPT overhead

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.



-----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.



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