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Re: What is acceptable for -ffast-math? (Was: associative law in combine)
- To: dewar at gnat dot com
- Subject: Re: What is acceptable for -ffast-math? (Was: associative law in combine)
- From: Joern Rennecke <amylaar at redhat dot com>
- Date: Tue, 31 Jul 2001 05:39:20 +0100 (BST)
- Cc: aoliva at redhat dot com, gdr at codesourcery dot com, amylaar at redhat dot com,gcc at gcc dot gnu dot org, moshier at moshier dot ne dot mediaone dot net,torvalds at transmeta dot com, tprince at computer dot org
> If you see a / 2.0 / 2.0
>
> it is absolutely definition OK, to compute this particular expression
> as a / 4.0 in any language no matter WHAT the standard says, since the
> result is exactly the same. But for other divisors this is not necessarily
No, if you have IEEE denormals, double rounding can give a different result.