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Re: RFC -- update_equiv_regs and friends
- To: Joern Rennecke <amylaar at cambridge dot redhat dot com>
- Subject: Re: RFC -- update_equiv_regs and friends
- From: Jeffrey A Law <law at redhat dot com>
- Date: Fri, 02 Mar 2001 01:26:49 -0700
- cc: john at feith dot com (John Wehle), gcc at gcc dot gnu dot org, rth at redhat dot com
- Reply-To: law at redhat dot com
In message <200103020236.f222a8i11812@phal.cambridge.redhat.com>you write:
> > 2) Change update_equiv_regs so it doesn't promote a REG_EQUAL note
> > to a REG_EQUIV if there's a register mentioned.
>
> Promoting REG_EQUAL to REG_EQUIV is an important optimization for some
> procesors for sums involving the stack pointer, the frame pointer,
> virtual_stack_var_rtx and the argument pointer.
True. But we can only do those promotions when we know those registers
are live and unchanging throughout the entire function. That is the
fundamental problem I see with the code as it stands right now.
jfef