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Re: [PATCH, i386]: Expand round(a) = sgn(a) * floor(fabs(a) + 0.5) using SSE4 ROUND insn

From: Uros Bizjak <ubizjak at gmail dot com>
To: gcc-patches at gcc dot gnu dot org
Date: Sun, 14 Aug 2011 20:00:38 +0200
Subject: Re: [PATCH, i386]: Expand round(a) = sgn(a) * floor(fabs(a) + 0.5) using SSE4 ROUND insn
References: <CAFULd4atDNoY-3gC9TkbTQ7P=r6fxtQ5F-Xf+Jk18fWP2Ga55g@mail.gmail.com>

On Sun, Aug 14, 2011 at 7:24 PM, Uros Bizjak <ubizjak@gmail.com> wrote:

> We can use ROUNDSP/ROUNDSD in round(a) expansion. Currently, we expand
> round(a) as (-O2 -ffast-math):

I forgot to add that this expansion is expanded only under
flag_unsafe_math_optimizations due to addition of 0.5. For the input
of 0x1.fffffffffffffp-2, new insn sequence returns 1.0.

Uros.

References:
- [PATCH, i386]: Expand round(a) = sgn(a) * floor(fabs(a) + 0.5) using SSE4 ROUND insn
  - From: Uros Bizjak

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