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Re: [Tinycc-devel] signed zero handling is still buggy


From: Michael Matz
Subject: Re: [Tinycc-devel] signed zero handling is still buggy
Date: Sun, 12 Jan 2014 19:25:38 +0100 (CET)
User-agent: Alpine 2.00 (LNX 1167 2008-08-23)

Hi,

On Sun, 12 Jan 2014, Vincent Lefevre wrote:

On 2014-01-12 04:59:06 +0100, Michael Matz wrote:
I think I've fixed that now on mob [1].  In particular +x is regarded as
no-op for floating point types (for integer types it's still x+0 so that the
promotions still happen automatically).  And unary -x is now expanded as
subtract(-0,x) for floating point types (hacking in real support for unary
operations would have been more complicated and would have entailed changes
in all backends).

subtract(-0,x) is OK in most cases, but in rounding toward -Inf,
on -0, one would get -0 instead of +0.

Yeah, I know, but tcc has many more problems with strict IEEE arithmetic and rouding modes, so I'll ignore that smallish aspect for now. Just don't switch rounding modes to -Inf when calculating -x ;-)


Ciao,
Michael.



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