dag combine sext(setcc) -> vsetcc before legalize. To make this safe,
VSETCC must define all bits, which is different than it was documented
to before. Since all targets that implement VSETCC already have this
behavior, and we don't optimize based on this, just change the
documentation. We now get nice code for vec_compare.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74978 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 609ec82..b10751b 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3071,14 +3071,32 @@
}
}
- // sext(setcc x, y, cc) -> (select_cc x, y, -1, 0, cc)
if (N0.getOpcode() == ISD::SETCC) {
+ // sext(setcc) -> sext_in_reg(vsetcc) for vectors.
+ if (VT.isVector() &&
+ // We know that the # elements of the results is the same as the
+ // # elements of the compare (and the # elements of the compare result
+ // for that matter). Check to see that they are the same size. If so,
+ // we know that the element size of the sext'd result matches the
+ // element size of the compare operands.
+ VT.getSizeInBits() == N0.getOperand(0).getValueType().getSizeInBits() &&
+
+ // Only do this before legalize for now.
+ !LegalOperations) {
+ return DAG.getVSetCC(N->getDebugLoc(), VT, N0.getOperand(0),
+ N0.getOperand(1),
+ cast<CondCodeSDNode>(N0.getOperand(2))->get());
+ }
+
+ // sext(setcc x, y, cc) -> (select_cc x, y, -1, 0, cc)
SDValue SCC =
SimplifySelectCC(N->getDebugLoc(), N0.getOperand(0), N0.getOperand(1),
DAG.getConstant(~0ULL, VT), DAG.getConstant(0, VT),
cast<CondCodeSDNode>(N0.getOperand(2))->get(), true);
if (SCC.getNode()) return SCC;
}
+
+
// fold (sext x) -> (zext x) if the sign bit is known zero.
if ((!LegalOperations || TLI.isOperationLegal(ISD::ZERO_EXTEND, VT)) &&