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From: Uros Bizjak <ubizjak@gmail.com>
Date: Wed, 23 Nov 2016 19:45:00 -0000
Message-ID: <CAFULd4b8H-FJ0hnrCp1pJqJdzTtO0PjquJ1-anOmKZf62BN31Q@mail.gmail.com>
Subject: Re: [3/3] Fix PR78120, in ifcvt/rtlanal/i386.
To: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: Bernd Schmidt <bschmidt@redhat.com>
Content-Type: text/plain; charset=UTF-8
X-SW-Source: 2016-11/txt/msg02437.txt.bz2

> 3. ifcvt computes the sum of costs for the involved blocks, but only
> makes a before/after comparison when optimizing for size. When
> optimizing for speed, it uses max_seq_cost, which is an estimate
> computed from BRANCH_COST, which in turn can be zero for predictable
> branches on x86.

Can you please correct the addition below? It makes me cry thinking
that buggy function will be immortalized in the gcc testsuite...

> +static inline u128 add_u128 (u128 a, u128 b)
> +{

  a.hi += b.hi;

> +  a.lo += b.lo;
> +  if (a.lo < b.lo)
> +    a.hi++;
> +
> +  return a;

Uros.