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[Bug target/20296] Speeding up small interrupts on avr
- From: "bjoern dot m dot haase at web dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 4 Mar 2005 19:51:24 -0000
- Subject: [Bug target/20296] Speeding up small interrupts on avr
- References: <20050302234747.20296.berndtrog@yahoo.com>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From bjoern dot m dot haase at web dot de 2005-03-04 19:51 -------
Hi,
IMHO everyone working on the avr back-end is aware of this problem. The
difficulty is, that the present architecture of the avr back-end does not
easily permit to improve this case: Every instruction pattern (like "multiply
two 16 bit integers" or "sign-extend a 16 bit variable to 32 bits") presently
is free to assume that may overwrite or change r0 and r1 unless it leaves the
"__zero_reg__" with 0 after finishing it's task.
Resolving this issue, IMHO, would require a major refactoring of the
back-end. ... IIUC the keyword is "replace all of the more complex instruction
patterns by RTL expressions."
I suggest to mark this bug as "desired enhancement".
Yours,
Björn
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20296