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Re: [PATCH][AArch64] Properly cost zero_extend+ashift forms of ubfi[xz]

From: Kyrill Tkachov <kyrylo dot tkachov at arm dot com>
To: GCC Patches <gcc-patches at gcc dot gnu dot org>
Cc: Marcus Shawcroft <marcus dot shawcroft at arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, James Greenhalgh <james dot greenhalgh at arm dot com>
Date: Fri, 11 Dec 2015 09:53:17 +0000
Subject: Re: [PATCH][AArch64] Properly cost zero_extend+ashift forms of ubfi[xz]
Authentication-results: sourceware.org; auth=none
References: <56615D45 dot 80408 at arm dot com>

Ping.
https://gcc.gnu.org/ml/gcc-patches/2015-12/msg00526.html

Thanks,
Kyrill

On 04/12/15 09:30, Kyrill Tkachov wrote:

Hi all,

We don't handle properly the patterns for the [us]bfiz and [us]bfx instructions when they
have an extend+ashift form. For example, the *<ANY_EXTEND:optab><GPI:mode>_ashl<SHORT:mode> pattern.
This leads to rtx costs recuring into the extend and assigning a cost to these patterns that is too
large.

This patch fixes that oversight.
I stumbled across this when working on a different combine patch and ended up matching the above
pattern, only to have it rejected for -mcpu=cortex-a53 due to the erroneous cost.

Bootstrapped and tested on aarch64.

Ok for trunk?

Thanks,
Kyrill

2015-12-04  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * config/aarch64/aarch64.c (aarch64_extend_bitfield_pattern_p):
    New function.
    (aarch64_rtx_costs, ZERO_EXTEND, SIGN_EXTEND cases): Use the above
    to handle extend+shift rtxes.

References:
- [PATCH][AArch64] Properly cost zero_extend+ashift forms of ubfi[xz]
  - From: Kyrill Tkachov

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