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Re: [PATCH] Small reg-stack improvement (PR target/70465)

From: Jeff Law <law at redhat dot com>
To: Jakub Jelinek <jakub at redhat dot com>, Uros Bizjak <ubizjak at gmail dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Wed, 22 Feb 2017 10:10:04 -0700
Subject: Re: [PATCH] Small reg-stack improvement (PR target/70465)
Authentication-results: sourceware.org; auth=none
References: <20170221212347.GY1849@tucnak>

On 02/21/2017 02:23 PM, Jakub Jelinek wrote:

Hi!

As reported by Uros, the
fld a
fld b
fxchg %st(1)
optimization to
fld b
fld a
misses several important cases, one is FLOAT_EXTEND memory loads where
the memory is SFmode or DFmode but we extend it to a wider mode, and
the other is when we load a known i?87 constant like 0.0, 1.0, PI etc.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-02-21  Jakub Jelinek  <jakub@redhat.com>

	PR target/70465
	* reg-stack.c (emit_swap_insn): Treat (float_extend:?F (mem:?F))
	and (const_double:?F) like (mem:?F) for the purpose of fxch %st(1)
	elimination by swapping fld*.

	* gcc.target/i386/pr70465-2.c: New test.

OK.
jeff

References:
- [PATCH] Small reg-stack improvement (PR target/70465)
  - From: Jakub Jelinek

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