[PATCH] Add a target legalize hook for SplitVectorOperand

[Justin Holewinski]

To be more specific, the X86 target declares that v2i64 extract_vector_elt
needs to be custom lowered:

    if (Subtarget->is64Bit()) {
      setOperationAction(ISD::INSERT_VECTOR_ELT,  MVT::v2i64, Custom);
      setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v2i64, Custom);
    }

But if the element type is i64 and the index is constant, then its lowered
to itself:

  if (VT == MVT::i32 || VT == MVT::i64) {
    // ExtractPS/pextrq works with constant index.
    if (isa<ConstantSDNode>(Op.getOperand(1)))
      return Op;
  }



Since this is specific to SSE 4.1, I could always add "-mattr=-sse41" to
the run line, but that would make the test X86-specific.




On Mon, Jul 22, 2013 at 8:50 PM, Justin Holewinski <
justin.holewinski at gmail.com> wrote:

> Unfortunately, it's not my lowering code.  This change triggers a
> legalization loop in CodeGen/Generic/2009-03-29-SoftFloatVectorExtract.ll
> when X86 is used as the default.  The X86 target lowers an i64
> extract_vector_elt to itself, causing the loop.  I don't know enough about
> the X86 custom lowering code to know where to start looking.  I'll see if I
> can identify the issue.
>  On Jul 22, 2013 6:05 PM, "Eli Friedman" <eli.friedman at gmail.com> wrote:
>
>> On Mon, Jul 22, 2013 at 10:10 AM, Justin Holewinski
>> <justin.holewinski at gmail.com> wrote:
>> > CustomLowerNode was not being called during SplitVectorOperand,
>> > meaning custom legalization could not be used by targets.
>> >
>> > Is there a reason this is missing, or just an oversight?
>> >
>> > This also adds a test case for NVPTX that depends on this custom
>> > legalization.
>> >
>> > http://llvm-reviews.chandlerc.com/D1195
>> >
>> > Files:
>> >   lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
>> >   lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
>> >   test/CodeGen/NVPTX/vector-stores.ll
>> >
>> > Index: lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
>> > ===================================================================
>> > --- lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
>> > +++ lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
>> > @@ -919,6 +919,11 @@
>> >      // The target didn't want to custom lower it after all.
>> >      return false;
>> >
>> > +  if (!LegalizeResult && Results[0].getNode() == N)
>> > +    // The target just returned the same node, so it must not have
>> wanted to
>> > +    // custom lower it after all.
>> > +    return false;
>>
>> Please fix your custom lowering implementation...
>>
>> >    // Make everything that once used N's values now use those in
>> Results instead.
>> >    assert(Results.size() == N->getNumValues() &&
>> >           "Custom lowering returned the wrong number of results!");
>> > Index: lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
>> > ===================================================================
>> > --- lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
>> > +++ lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
>> > @@ -1031,6 +1031,10 @@
>> >          dbgs() << "\n");
>> >    SDValue Res = SDValue();
>> >
>> > +  // See if the target wants to custom split this node.
>> > +  if (CustomLowerNode(N, N->getOperand(OpNo).getValueType(), false))
>> > +    return false;
>> > +
>> >    if (Res.getNode() == 0) {
>> >      switch (N->getOpcode()) {
>> >      default:
>>
>> This looks fine.
>>
>> -Eli
>>
>


-- 

Thanks,

Justin Holewinski
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