From: Jakub Jelinek <jakub@redhat.com>
To: Simon Richter <Simon.Richter@hogyros.de>,
Segher Boessenkool <segher@kernel.crashing.org>,
David Edelsohn <dje.gcc@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: POWER __builtin_add_overflow/__builtin_mul_overflow with u64
Date: Tue, 14 Feb 2023 09:23:55 +0100 [thread overview]
Message-ID: <Y+tFG7lMckrx7zGF@tucnak> (raw)
In-Reply-To: <567bf141-3d8b-201f-933b-087db28fc38b@hogyros.de>
Hi!
CCing Segher and David on this.
rs6000 indeed doesn't implement {,u}{add,sub,mul}v4_optab for
any mode and thus leaves it to the generic code.
On Tue, Feb 14, 2023 at 04:48:42AM +0100, Simon Richter wrote:
> I'm looking at the generated code for these builtins on POWER:
>
> add 4,3,4
> subfc 3,3,4
> subfe 3,3,3
> std 4,0(5)
> rldicl 3,3,0,63
> blr
>
> and
>
> mulld 10,3,4
> mulhdu 3,3,4
> addic 9,3,-1
> std 10,0(5)
> subfe 3,9,3
> blr
>
> The POWER architecture has variants of these instructions with builtin
> overflow checks (addo/mulldo), but these aren't listed in the .md files, and
> the builtins don't generate them either.
>
> Is this intentional (I've found a few comments that mulldo is microcoded on
> CellBE and should be avoided there)?
Jakub
next prev parent reply other threads:[~2023-02-14 8:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 3:48 Simon Richter
2023-02-14 8:23 ` Jakub Jelinek [this message]
2023-02-14 9:26 ` Eric Botcazou
2023-02-15 9:43 ` Segher Boessenkool
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