[llvm-commits] [llvm-gcc-4.2] r82640 - /llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp

[Evan Cheng]

On Sep 23, 2009, at 2:18 PM, Dale Johannesen wrote:

> While this is certainly necessary given the current IR definition, I'm
> not too happy about it, as we will lose something because the
> optimizers must consider that sqrt might set errno.  What I'd like to
> do is redefine llvm.sqrt in the IR to mean "same behavior as sqrt
> except that it doesn't set errno", and likewise for llvm.pow, etc.  It
> looks like that was the original intent, actually, but that's not what
> it says.  Any objections?

Are we doing any optimizations on llvm.sqrt?

Evan

>
> On Sep 23, 2009, at 11:50 AMPDT, Dale Johannesen wrote:
>
>> Author: johannes
>> Date: Wed Sep 23 13:50:32 2009
>> New Revision: 82640
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=82640&view=rev
>> Log:
>> The result of sqrt(negative) is implementation-defined, but follows
>> IEEE754 in most current implementations. llvm.sqrt, which has
>> undefined
>> behavior for such inputs, is an inappropriate substitute which can
>> change
>> the result.
>
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