[Bug target/20296] Speeding up small interrupts on avr

[bjoern dot m dot haase at web dot de]

------- 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 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20296