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Re: Use-and-clobber insns and some ancient combine.c code
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: weigand at i1 dot informatik dot uni-erlangen dot de
- Cc: gcc at gcc dot gnu dot org
- Date: Thu, 17 Jun 04 09:49:40 EDT
- Subject: Re: Use-and-clobber insns and some ancient combine.c code
I guess I can see why we wouldn't want to substitute into the operand
of a CLOBBER itself. But why prevent substitution of an expression
containing a register that will be clobbered? This second clause was
added under this ChangeLog entry:
I don't remember the second issue, but as to this one, I think the
point is that you can't selectively substitute into the insn, so you
would update the CLOBBER. But I'm not sure.