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Re: Reload with jump_insn that have a 'set' side effect.
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: Hendrik Greving <hendrik dot greving dot intel at gmail dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 18 Sep 2013 08:26:52 +0100
- Subject: Re: Reload with jump_insn that have a 'set' side effect.
- Authentication-results: sourceware.org; auth=none
- References: <CANc4vhpQzdTfKdZ6TXw46LcrBQWhsBNFzEvKp6m1SHxC1=hfkQ at mail dot gmail dot com> <87y56vic9a dot fsf at talisman dot default> <CANc4vhq3cLqGHZd7sNc6bBWFb_YTCshF6aV_5xMUtsLeuHxNcQ at mail dot gmail dot com>
Hendrik Greving <hendrik.greving.intel@gmail.com> writes:
> One follow-up question here. Is it of any disadvantage to always
> generate a clobber (scratch) during expansion? Meaning that in the
> case we don't need one (we won't split, which I am checking with
> memory_operand(myoutput_operand), that register won't get allocated
> and adds to register pressure, does it?
Yeah, the idea is that if the match_scratch isn't needed for a particular
alternative, the constraint for that alternative should be "X" rather than
a register class. That way the (scratch) stays a (scratch) even after
register allocation.
Thanks,
Richard