SplitRes_SELECT improvement

[Relph, Richard]

On Mar 12, 2013, at 9:30 AM, Nadav Rotem <nrotem at apple.com<mailto:nrotem at apple.com>>
 wrote:

Richard,

The assertion that you suggested that we remove is about something different. It checks that the result of the select node is legalized before the condition.  Can you show us the SDNode that fails on this assertion ?

Not at the moment… ;-) With your fix to visitSIGN_EXTEND, this problem seems to have disappeared...


Thanks,
Nadav

On Mar 12, 2013, at 9:25 AM, Duncan Sands <baldrick at free.fr<mailto:baldrick at free.fr>> wrote:

Hi Richard,

On 12/03/13 16:00, Relph, Richard wrote:
DAGTypeLegalizer::SplitRes_SELECT() currently does an assert if the condition is not of type MVT::i1. This patch uses the existing type of the condition to generate the type for the split conditions instead of a fixed i1.
This is an issue for us when trying to legalize a 8x or 16x vector to a 4x type… it isn't the case that we always have an MVT::i1 condition coming in.

if the select condition is a vector then you should be using a vselect node
rather than a select node.  So I think this patch is wrong and the real problem
is that the wrong select node type is being generated somewhere.

Ciao, Duncan.


Index: lib/CodeGen/SelectionDAG/LegalizeTypesGeneric.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeTypesGeneric.cpp (revision 176837)
+++ lib/CodeGen/SelectionDAG/LegalizeTypesGeneric.cpp (working copy)
@@ -490,10 +490,10 @@
   SDValue Cond = N->getOperand(0);
   CL = CH = Cond;
   if (Cond.getValueType().isVector()) {
-    assert(Cond.getValueType().getVectorElementType() == MVT::i1 &&
-           "Condition legalized before result?");
     unsigned NumElements = Cond.getValueType().getVectorNumElements();
-    EVT VCondTy = EVT::getVectorVT(*DAG.getContext(), MVT::i1, NumElements / 2);
+    EVT VCondTy = EVT::getVectorVT(*DAG.getContext(),
+                                   Cond.getValueType().getVectorElementType(),
+                                   NumElements / 2);
     CL = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, VCondTy, Cond,
                      DAG.getIntPtrConstant(0));
     CH = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, VCondTy, Cond,



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