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[PATCH, i386]: Fix PR78794, ~9% regression in 32-bit mode for 462.libquntum on Avoton after r243202

From: Uros Bizjak <ubizjak at gmail dot com>
To: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
Date: Tue, 13 Dec 2016 18:23:37 +0100
Subject: [PATCH, i386]: Fix PR78794, ~9% regression in 32-bit mode for 462.libquntum on Avoton after r243202
Authentication-results: sourceware.org; auth=none

Hello!

Attached patch fixes STV cost function to better model gains of pandn
insn on non-BMI targets. As explained in the PR, STV converts four
scalar arithmetic insns (2 * not and 2 * and) to one (pandn). The
patch increases gain for non-BMI targets for 2 * ix86_cost->add to a
total of 3 * ix86_cost->add.

2016-12-13  Uros Bizjak  <ubizjak@gmail.com>

    PR target/78794
    * config/i386/i386.c (dimode_scalar_chain::compute_convert_gain):
    Calculate additional gain for andnot for targets without BMI.

testsuite/ChangeLog:

2016-12-13  Uros Bizjak  <ubizjak@gmail.com>

    PR target/78794
    * gcc.target/i386/pr78794.c: New test.

Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Committed to mainline SVN.

Uros.

Attachment: p.diff.txt
Description: Text document

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