llvm dev - Mar 2010 - [LLVMdev] folding x * 0 = 0

> Is x*0 =>  0 true if isnan(x)?
>    
then where do I have to add it if I want to make it a non-standard 
modification
of my local llvm version?
would it make sense to add a subset of float to llvm or a kind of modifier
(e.g. valid float to indicate that it is always valid and not nan) to 
allow more aggressive optimization?
just like e.g. inbounds for load

-Jochen

On Mar 3, 2010, at 9:32 AM, Jochen Wilhelmy wrote:
> 
>> Is x*0 =>  0 true if isnan(x)?
>> 
> then where do I have to add it if I want to make it a non-standard 
> modification
> of my local llvm version?
> would it make sense to add a subset of float to llvm or a kind of modifier
> (e.g. valid float to indicate that it is always valid and not nan) to 
> allow more aggressive optimization?
> just like e.g. inbounds for load
You should check out the -enable-finite-only-fp-math and -enable-unsafe-fp-math
options.

> You should check out the -enable-finite-only-fp-math and
-enable-unsafe-fp-math options.
Good hint, but

     llvm::UnsafeFPMath = true;
     llvm::FiniteOnlyFPMathOption = true;

at the beginning of my code does not help.
I found llvm::Reassociate::OptimizeExpression in 
llvm\lib\Transforms\Scalar\Reassociate.cpp
which looks like it does X * 0 = 0 for int, but it does not get called 
for int,
but it works for int.

-Jochen