From: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sparse Mailing-list <linux-sparse@vger.kernel.org>
Subject: Re: [PATCH 1/7] not: add testcases for canonicalization & simplification of negations
Date: Sun, 22 Nov 2020 21:38:00 +0100 [thread overview]
Message-ID: <20201122203800.y262kn5hk3puvcbh@ltop.local> (raw)
In-Reply-To: <CAHk-=wjoJXrG=2_vnOX37fro12eyZc+uo2WL+F-utk51g9WuBA@mail.gmail.com>
On Sun, Nov 22, 2020 at 12:13:46PM -0800, Linus Torvalds wrote:
>
> Honestly, particularly in the conditional form, the OP_SEL
> optimization might not even be the right thing. It adds register
> pressure.
>
> So maybe a better model would be to not try to do jump-conversion, but
> have some kind of general "can we simplify phi nodes", where jump
> conversion to OP_SEL is just one of the options.
Yes, for the "context imbalance" problem, it's best to eliminate
the most possible conditional branches (and if-conversion and jump
threading help each other at this (when not blocking each other)).
So, yes, probably what's missing the most is some strategy to
attack the problem.
-- Luc
next prev parent reply other threads:[~2020-11-22 20:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-22 15:27 [PATCH 0/7] simplify logical negation Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 1/7] not: add testcases for canonicalization & simplification of negations Luc Van Oostenryck
2020-11-22 19:00 ` Linus Torvalds
2020-11-22 19:57 ` Luc Van Oostenryck
2020-11-22 20:13 ` Linus Torvalds
2020-11-22 20:38 ` Luc Van Oostenryck [this message]
2020-11-22 22:26 ` Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 0/6] 'bits translation' simplification Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 1/6] add testscases for 'bits translation' optimization Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 2/6] factorize SEL(x, OP(y,z), y) into OP(SEL(x, z, 0), y) Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 3/6] add helper is_power_of_2() Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 4/6] add helper is_pow2() Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 5/6] add log base 2 function: log2_exact() Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 6/6] convert SEL(x & BIT1, BIT2, 0) into SHIFT(x & BIT1, S) Luc Van Oostenryck
2020-11-27 22:25 ` [PATCH 7/7] move up instructions blocking if-conversion Luc Van Oostenryck
2020-11-27 22:44 ` [PATCH 0/6] 'bits translation' simplification Linus Torvalds
2020-11-22 15:27 ` [PATCH 2/7] canon: put PSEUDO_ARGs in canonical order too Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 3/7] canon: put PSEUDO_REGs " Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 4/7] canon: simplify calculation of canonical order Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 5/7] opcode: add helpers opcode_negate() & opcode_swap() Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 6/7] not: simplify (~x {&,|,^} x) --> {0,~0,~0} Luc Van Oostenryck
2020-11-22 15:27 ` [PATCH 7/7] not: simplify ((x cmp y) {&,|,^} (x !cmp y)) --> {0,1,1} Luc Van Oostenryck
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