r227956 - Add some overloads so that floating point literals can be AST matched properly.

[Daniel Jasper]

This is for matching float literals and for that it should provide good
enough value. I don't think people will want to match the result of
computations here and if they do want that, we can add more complex
matchers.

On Tue, Feb 3, 2015 at 6:41 PM, Kim Gräsman <kim.grasman at gmail.com> wrote:

> Hi Daniel,
>
> On Tue, Feb 3, 2015 at 10:45 AM, Daniel Jasper <djasper at google.com> wrote:
> > Author: djasper
> > Date: Tue Feb  3 03:45:52 2015
> > New Revision: 227956
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=227956&view=rev
> > Log:
> > Add some overloads so that floating point literals can be AST matched
> properly.
> >
> > I am not entirely sure whether the implemented sematics are ideal. In
> > particular, should floatLiteral(equals(0.5)) match "0.5f" and should
> > floatLiteral(equals(0.5f)) match "0.5". With the overloads in this
> > patch, the answer to both questions is yes, but I am happy to change
> > that.
>
> This looks scary to me given the general difficulties in comparing floats:
> https://randomascii.wordpress.com/2013/07/16/floating-point-determinism/
>
> Or is it safe because they're both fixed literals and not the result
> of a calculation? Then again, nothing prevents me from doing;
>
>   floatLiteral(equals(sqrt(AnArgument)))
>
> - Kim
>
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