[Bug optimization/15265] delete_output_reload deletes necessary insn

[joern dot rennecke at superh dot com]

------- Additional Comments From joern dot rennecke at superh dot com  2004-05-06 14:17 -------
Subject: Re:  delete_output_reload deletes necessary insn

> Even with SUBREGs or such I have these difficulties.  For instance if there is 
> a "(set (subreg (reg X) 0) plus (subreg (reg X) 0) (subreg (reg X) 0))" 
> and reg X must be reloaded, but only (!) in the first operand of the plus, 
> which must match the destination. 

For some SUBREGs, a USE and/or CLOBBER is placed into the instruction
stream to describe the operand as it looked prior to reloading.

I'm not saying that we must always do double counting; what I'm saying is
that when we eliminate I in some cases, we should check that there isn't
double counting of the operands to match it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15265