Re: check_ext_dependent_givs

[Canqun Yang <canqun at nudt dot edu dot cn>]

Hi, Bonzini,

Thank you for your reponse.
I do not want to modify the old loop optimizer defined 
in loop.c.  I am preparing to port some improvements 
done on gcc-3.5 to gcc-4.0, and the GIV optimizations 
is part of my concerns.

On IA-64, the GIV optimization can hardly improve the 
performance. The reason is that 
check_ext_dependent_givs can not giv an exactly answer 
whether the BIVs will be wrap around or not. In most 
cases, it only produce a conservative result that the 
BIVs may overflow and the corresponding GIVs can not 
be reduced. 

I modified the code in check_ext_dependent_givs to let 
the BIVs always successfully pass the check, then test 
the example you have given to me, but the result is 
the same as before.

Would you please give me another example which will 
lead a wrong result if the check_ext_dependnet_givs 
has not been called. FORTRAN program is nice, and my 
platform is a 64bit system.

Best regards,

Canqun Yang
Creative Compiler Research Group.
National University of Defense Technology, China.