[llvm-commits] Fold multiply by 0 and 1 when in UnsafeFPMath mode in SelectionDAG::getNode()

[Peter Cooper]

Oops, my bad.  Then return SDValue(Arg, 0) is what you need.
On Sep 7, 2012, at 5:07 PM, Michael Ilseman <milseman at apple.com> wrote:

> I should mention my return type is SDValue, so I'm trying to go from SDNode to SDValue in this case.
> 
> On Sep 7, 2012, at 5:04 PM, Peter Cooper <peter_cooper at apple.com> wrote:
> 
>> N1.getNode() will do it too.
>> 
>> Pete
>> On Sep 7, 2012, at 5:03 PM, Michael Ilseman <milseman at apple.com> wrote:
>> 
>>> Unfortunately, CFP is an SDNode: the assignment statement with dyncast ends up calling the SDValue's *operator. I could probably call the SDValue constructor on CFP, and in that case would the resno just be 0?
>>> 
>>> On Sep 7, 2012, at 4:59 PM, Chandler Carruth <chandlerc at google.com> wrote:
>>> 
>>>> 
>>>> On Fri, Sep 7, 2012 at 7:55 PM, Michael Ilseman <milseman at apple.com> wrote:
>>>> Thanks for the comment. New patch attached. I'm not too familiar with SDValue/SDNode, so if you see a way that it can be cleaned up further, let me know!
>>>> 
>>>> Hmm, I would have assumed (naively, and without running the compiler over it) that you could write this as:
>>>> 
>>>>       } else if (Opcode == ISD::FMUL) {
>>>>         ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N1);
>>>>         SDNode *Arg = N2;
>>>> 
>>>>         // If the first operand isn't the constant, try the second
>>>>         if (!CFP) {
>>>>           CFP = dyn_cast<ConstantFPSDNode>(N2);
>>>>           Arg = N1;
>>>>         }
>>>> 
>>>>         if (CFP) {
>>>>           // 0*x --> 0
>>>>           if (CFP->isZero())
>>>>             return CFP;
>>>>           // 1*x --> x
>>>>           if (CFP->isExactlyValue(1.0))
>>>>             return Arg;
>>>>         }
>>>> 
>>>> If that doesn't work, your version seems fine.
>>> 
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>> 
> 

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