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Date: Tue, 21 Jan 2020 08:11:50 +1100 (AEDT)
From: Damian McGuckin <damianm@....com.au>
To: musl@...ts.openwall.com
Subject: Triggering Overflow (or Underflow) without triggering Inexact on
i386
I am trying to write arithmetic expressions using only x87 instructions to
trigger an exception. The ASM instruction to raise the flag in the status
register has way too much overhead.
My normal technique of doing either of these would also trigger Inexact.
e.g.
volatile long double t;
Overflow: t = largest normal long double, t *= t;
Underflow: t = smallest normal long double, t *= t;
Can it be triggered WITHOUT also triggering INEXACT?
Regards - Damian
Pacific Engineering Systems International, 277-279 Broadway, Glebe NSW 2037
Ph:+61-2-8571-0847 .. Fx:+61-2-9692-9623 | unsolicited email not wanted here
Views & opinions here are mine and not those of any past or present employer
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