Teach the SelectionDAG how to transform select_cc eq, X, 0, 1, 0 into
either seteq X, 0 or srl (ctlz X), size(X-1), depending on what's legal
for the target.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22978 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3bae15c..3ebaaa4 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -853,6 +853,23 @@
}
}
+ // Check to see if this is the equivalent of seteq X, 0.
+ // select_cc seteq X, 0, 1, 0 -> setcc X, 0, seteq -> srl (ctlz X), size(X)-1
+ if (N2C && N2C->isNullValue() && N4C && N4C->isNullValue() &&
+ N3C && (N3C->getValue() == 1)) {
+ MVT::ValueType XType = N1.getValueType();
+ if (TLI.getOperationAction(ISD::SETCC, TLI.getSetCCResultTy()) ==
+ TargetLowering::Legal) {
+ return getSetCC(TLI.getSetCCResultTy(), N1, N2, ISD::SETEQ);
+ }
+ if (TLI.getOperationAction(ISD::CTLZ, XType) == TargetLowering::Legal) {
+ SDOperand Ctlz = getNode(ISD::CTLZ, XType, N1);
+ return getNode(ISD::SRL, XType, Ctlz,
+ getConstant(MVT::getSizeInBits(XType)-1,
+ TLI.getShiftAmountTy()));
+ }
+ }
+
// Check to see if this is an integer abs. select_cc setl[te] X, 0, -X, X ->
// Y = sra (X, size(X)-1); xor (add (X, Y), Y)
if (N2C && N2C->isNullValue() && (CC == ISD::SETLT || CC == ISD::SETLE) &&