ISel: Make VSELECT selection terminate in cases where the condition type has to

be split and the result type widened.

When the condition of a vselect has to be split it makes no sense widening the
vselect and thereby widening the condition. We end up in an endless loop of
widening (vselect result type) and splitting (condition mask type) doing this.
Instead, split both the condition and the vselect and widen the result.

I ran this over the test suite with i686 and mattr=+sse and saw no regressions.

Fixes PR18036.

llvm-svn: 203311

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 2db913d4f1e..4f57bc32011 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -2192,6 +2192,17 @@ SDValue DAGTypeLegalizer::WidenVecRes_SELECT(SDNode *N) {
     if (getTypeAction(CondVT) == TargetLowering::TypeWidenVector)
       Cond1 = GetWidenedVector(Cond1);
 
+    // If we have to split the condition there is no point in widening the
+    // select. This would result in an cycle of widening the select ->
+    // widening the condition operand -> splitting the condition operand ->
+    // splitting the select -> widening the select. Instead split this select
+    // further and widen the resulting type.
+    if (getTypeAction(CondVT) == TargetLowering::TypeSplitVector) {
+      SDValue SplitSelect = SplitVecOp_VSELECT(N, 0);
+      SDValue Res = ModifyToType(SplitSelect, WidenVT);
+      return Res;
+    }
+
     if (Cond1.getValueType() != CondWidenVT)
       Cond1 = ModifyToType(Cond1, CondWidenVT);
   }