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Re: PR63633: May middle-end come up width hard regs for insn expanders?

From: Jeff Law <law at redhat dot com>
To: Jakub Jelinek <jakub at redhat dot com>, Georg-Johann Lay <avr at gjlay dot de>
Cc: GCC Development <gcc at gcc dot gnu dot org>
Date: Tue, 28 Oct 2014 07:39:48 -0600
Subject: Re: PR63633: May middle-end come up width hard regs for insn expanders?
Authentication-results: sourceware.org; auth=none
References: <544A5C14 dot 5030607 at gjlay dot de> <544A7CFA dot 700 at redhat dot com> <20141024162919 dot GL10376 at tucnak dot redhat dot com> <544A7EE5 dot 1040303 at redhat dot com> <544A984D dot 8080804 at gjlay dot de> <20141024182950 dot GQ10376 at tucnak dot redhat dot com> <544E9DFD dot 5040401 at gjlay dot de> <544EA045 dot 1030503 at redhat dot com> <544F86CE dot 5030401 at gjlay dot de> <20141028124054 dot GI10376 at tucnak dot redhat dot com>

On 10/28/14 06:40, Jakub Jelinek wrote:


I'd say if on the target reg26 or reg27 is used or clobbered by
multiplication, then it is a user error to use it this way, the register
then isn't suitable for the local hard register usage.

Right.

And this situation is a great example of why clobbering hard registersin patterns is a bad idea.

This has a much greater chance of working if the patterns insteadclobbered a pseudo/scratch where the constraint specifies a class thathas r26/r27 as a member (possibly its only member).


Jeff

References:
- PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Georg-Johann Lay
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jeff Law
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jakub Jelinek
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jeff Law
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Georg-Johann Lay
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jakub Jelinek
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Georg-Johann Lay
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jeff Law
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Georg-Johann Lay
- Re: PR63633: May middle-end come up width hard regs for insn expanders?
  - From: Jakub Jelinek

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