[llvm-commits] CVS: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

[Evan Cheng]

Doh. Brain cramp.

Evan
On Apr 30, 2007, at 9:39 PM, Chris Lattner wrote:

>> +    bool HasUses = false;
>> +    SmallVector<MVT::ValueType, 2> VTs;
>> +    for (unsigned i = 0, e = N->getNumValues(); i != e; ++i) {
>> +      if (!N->hasNUsesOfValue(0, i)) {
>> +        HasUses = true;
>> +        break;
>> +      }
>> +      VTs.push_back(N->getValueType(i));
>> +    }
>> +    if (!HasUses) {
>> +      SmallVector<SDOperand, 1> Ops;
>> +      return CombineTo(N, DAG.getNode(ISD::UNDEF, &VTs[0], VTs.size
>> (), 0, 0),
>> +                       Chain);
>
> This can never trigger and isn't right if it did.
>
> #1: This should trigger if the chain has uses but the other values do
> not.  If the entire node is dead, it will already have been removed.
>
> #2. you can't create an undef with multiple results, you have to
> create multiple undefs :)
>
> I'd suggest just writing this as:
>
>    if (N->getValueType(1) == MVT::Other) {
>      // single result case.
>    } else {
>      assert(N->getValueType(2) == MVT::Other);
>      // multi result case.
>    }
>
> This lets you drop the looping and smallvector.
>
> -Chris
>
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