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Re: [PATCH 2/2] target/i386: fix IEEE x87 floating-point exception raisi
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From: |
Joseph Myers |
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Subject: |
Re: [PATCH 2/2] target/i386: fix IEEE x87 floating-point exception raising |
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Date: |
Tue, 19 May 2020 18:28:27 +0000 |
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User-agent: |
Alpine 2.21 (DEB 202 2017-01-01) |
On Tue, 19 May 2020, Richard Henderson wrote:
> > Note that another bug in the x87 emulation is the lack of setting C1 for
> > most instructions with inexact results based on the direction of rounding
> > (which will require a new feature to be added to the softfloat code to
> > record that information so the x87 emulation can use it).
>
> Wow, I don't believe I ever knew about that detail.
musl libc uses it to get correctly rounded double-precision sqrt with x87
arithmetic. (glibc instead temporarily sets the rounding precision to
achieve the same goal.)
--
Joseph S. Myers
address@hidden