[LLVMdev] how the fptrunc ... to .... is supported

[Mehdi Amini]

> On May 24, 2015, at 9:04 PM, Zhang, Kewu <Kewu.Zhang at amd.com> wrote:
> 
> Dear experts.
> 
> I am curious how the "<targettype> = fptrunc <sourcetype> <value> to <targettype>" is supported by the backends?  I searched all llvm directory with "fptrunc" key words, no lucky.
> 
> Is it supported by the front end itself?
> 
> if I have to support/overide it, which ISD node I should map to?
> why there is no such a node like "fptrunc" is defined  so I can write patterns for it?

I think that the SelectionDAG node that corresponds to fptrunc is called FP_ROUND. 

http://llvm.org/docs/doxygen/html/namespacellvm_1_1ISD.html <http://llvm.org/docs/doxygen/html/namespacellvm_1_1ISD.html>


FP_ROUND 	 X = FP_ROUND(Y, TRUNC) - Rounding 'Y' from a larger floating point type down to the precision of the destination VT. 
TRUNC is a flag, which is always an integer that is zero or one. If TRUNC is 0, this is a normal rounding, if it is 1, this FP_ROUND is known to not change the value of Y.


— 
Mehdi

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