[llvm] r237423 - Add SDNodes for umin, umax, smin and smax.

[James Molloy]

Hi Matt,

Apologies, this looks like a think-o on my part. You’re right, it should be SDAGBuilder’s job to filter out cases where the condition has multiple users.

I’ve committed a fix for this in r239037.

Cheers,

James

On 3 Jun 2015, at 21:59, Matt Arsenault <arsenm2 at gmail.com> wrote:

>
>> On May 15, 2015, at 2:03 AM, James Molloy <james.molloy at arm.com> wrote:
>>
>>
>> -  for (unsigned i = 0; i != NumValues; ++i)
>> +  // Min/max matching is only viable if all output VTs are the same.
>> +  if (std::equal(ValueVTs.begin(), ValueVTs.end(), ValueVTs.begin())) {
>> +    Value *LHS, *RHS;
>> +    SelectPatternFlavor SPF = matchSelectPattern(const_cast<User*>(&I), LHS, RHS);
>> +    ISD::NodeType Opc = ISD::DELETED_NODE;
>> +    switch (SPF) {
>> +    case SPF_UMAX: Opc = ISD::UMAX; break;
>> +    case SPF_UMIN: Opc = ISD::UMIN; break;
>> +    case SPF_SMAX: Opc = ISD::SMAX; break;
>> +    case SPF_SMIN: Opc = ISD::SMIN; break;
>> +    default: break;
>> +    }
>> +
>
> Hi,
>
> I’m trying to port R600’s target nodes to use this and hitting a problem from this. matchSelectPattern always matches, even if the condition has multiple uses. If you do something else to the condition besides the min/max, this increases the instruction count. What is the intended behavior / other uses of matchSelectPattern? Should it be rejecting cases with multiple condition uses, or should these cases be filtered out here in SelectionDAGBuilder?
>
> -Matt
>


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