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

[Peter Cooper]

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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