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From: Simon Richter <Simon.Richter@hogyros.de>
To: gcc@gcc.gnu.org
Subject: POWER __builtin_add_overflow/__builtin_mul_overflow with u64
Date: Tue, 14 Feb 2023 04:48:42 +0100	[thread overview]
Message-ID: <567bf141-3d8b-201f-933b-087db28fc38b@hogyros.de> (raw)


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Hi,

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)?

    Simon

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             reply	other threads:[~2023-02-14  3:48 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-14  3:48 Simon Richter [this message]
2023-02-14  8:23 ` Jakub Jelinek
2023-02-14  9:26   ` Eric Botcazou
2023-02-15  9:43   ` Segher Boessenkool

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