Multiple cse and loop opts

Michael Hayes m.hayes@elec.canterbury.ac.nz
Sun Jan 31 23:58:00 GMT 1999


Jeffrey A Law writes:
 >   In message < 199901100425.WAA32150@isua5.iastate.edu >you write:
 >   > 
 >   >   Are there any bad consequences of adding a second loop optimization
 >   > followed by a third CSE pass, other than increase in compilation time?
 >   > I have been playing with two loops under egcs v1.1.1 that look like
 >   > these:
 > I'd recommend against it.  It's going to slow the compiler down with marginal
 > benefit.  I don't think you'll find much real code that will show any real
 > benefit from adding another loop & cse pass.

What is probably of more benefit is a pass to mop up after reload;
removing redundant moves and especially hoisting invariant reloads out
of loops.

How feasible is it to use the gcse/pre stuff for this after reload?

Michael.



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