From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] tree-optimization/114074 - CHREC multiplication and undefined overflow
Date: Mon, 26 Feb 2024 15:22:43 +0100 [thread overview]
Message-ID: <Zdyes9V+OUIBCygR@tucnak> (raw)
In-Reply-To: <83476.124022609150401789@us-mta-131.us.mimecast.lan>
On Mon, Feb 26, 2024 at 03:15:02PM +0100, Richard Biener wrote:
> When folding a multiply CHRECs are handled like {a, +, b} * c
> is {a*c, +, b*c} but that isn't generally correct when overflow
> invokes undefined behavior. The following uses unsigned arithmetic
> unless either a is zero or a and b have the same sign.
>
> I've used simple early outs for INTEGER_CSTs and otherwise use
> a range-query since we lack a tree_expr_nonpositive_p.
What about testing
(get_range_pos_neg (CHREC_LEFT (op0))
| get_range_pos_neg (CHREC_RIGHT (op0))) != 3
?
Jakub
next parent reply other threads:[~2024-02-26 14:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <83476.124022609150401789@us-mta-131.us.mimecast.lan>
2024-02-26 14:22 ` Jakub Jelinek [this message]
2024-02-26 14:29 ` Richard Biener
2024-02-26 14:45 ` Jakub Jelinek
2024-02-26 15:51 ` Michael Matz
2024-02-26 15:56 ` Jakub Jelinek
[not found] <20240226141510.C27103858C33@sourceware.org>
2024-02-26 16:02 ` Jakub Jelinek
2024-02-26 14:15 Richard Biener
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