[LLVMdev] Generating Floating point constants

Stéphane Letz letz at free.fr
Wed Jun 2 03:28:01 PDT 2010

Le 2 juin 2010 à 12:21, Eli Friedman a écrit :

> On Wed, Jun 2, 2010 at 2:59 AM, Stéphane Letz <letz at free.fr> wrote:
>> Hi,
>> We need to generate "Floating point constants" in our code. In http://llvm.org/docs/LangRef.html it is explained that FP has to follow special encoding rules to be handled by LLVM later one (hexadecimal coding...)
>> Is there any code available in LLVM  to handle this kind of "standard float to LLVM float" conversion?
> If you're writing C++ code, just stick your float into an APFloat and
> doesn't worry about the hexadecimal coding.  If you're generating
> textual IR,

Yes we are generating textual IR,

> and you don't care about the precise hexadecimal
> representation, AFAIK just printing a decimal float works.  

Seems like some values cannot be assembled later on (for instance with "llc")

> If you
> really want a hexadecimal encoding, just reinterpret the
> floating-point number as an integer and print in hexadecimal; an "LLVM
> float" is just an IEEE float printed in hexadecimal.

I will try.


Stéphane Letz

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