Pattern match a setcc of boolean value with 0 as a truncate.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154322 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1d135ef..dbc1ca9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4408,6 +4408,44 @@
return SDValue();
}
+// isTruncateOf - If N is a truncate of some other value, return true, record
+// the value being truncated in Op and which of Op's bits are zero in KnownZero.
+// This function computes KnownZero to avoid a duplicated call to
+// ComputeMaskedBits in the caller.
+static bool isTruncateOf(SelectionDAG &DAG, SDValue N, SDValue &Op,
+ APInt &KnownZero) {
+ APInt KnownOne;
+ if (N->getOpcode() == ISD::TRUNCATE) {
+ Op = N->getOperand(0);
+ DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
+ return true;
+ }
+
+ if (N->getOpcode() != ISD::SETCC || N->getValueType(0) != MVT::i1 ||
+ cast<CondCodeSDNode>(N->getOperand(2))->get() != ISD::SETNE)
+ return false;
+
+ SDValue Op0 = N->getOperand(0);
+ SDValue Op1 = N->getOperand(1);
+ assert(Op0.getValueType() == Op1.getValueType());
+
+ ConstantSDNode *COp0 = dyn_cast<ConstantSDNode>(Op0);
+ ConstantSDNode *COp1 = dyn_cast<ConstantSDNode>(Op1);
+ if (COp0 && COp0->getZExtValue() == 0)
+ Op = Op1;
+ else if (COp1 && COp1->getZExtValue() == 0)
+ Op = Op0;
+ else
+ return false;
+
+ DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
+
+ if (!(KnownZero | APInt(Op.getValueSizeInBits(), 1)).isAllOnesValue())
+ return false;
+
+ return true;
+}
+
SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
SDValue N0 = N->getOperand(0);
EVT VT = N->getValueType(0);
@@ -4425,15 +4463,16 @@
// (zext (truncate x)) -> (truncate x)
// This is valid when the truncated bits of x are already zero.
// FIXME: We should extend this to work for vectors too.
- if (N0.getOpcode() == ISD::TRUNCATE && !VT.isVector()) {
- SDValue Op = N0.getOperand(0);
- APInt TruncatedBits
- = APInt::getBitsSet(Op.getValueSizeInBits(),
- N0.getValueSizeInBits(),
- std::min(Op.getValueSizeInBits(),
- VT.getSizeInBits()));
- APInt KnownZero, KnownOne;
- DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
+ SDValue Op;
+ APInt KnownZero;
+ if (!VT.isVector() && isTruncateOf(DAG, N0, Op, KnownZero)) {
+ APInt TruncatedBits =
+ (Op.getValueSizeInBits() == N0.getValueSizeInBits()) ?
+ APInt(Op.getValueSizeInBits(), 0) :
+ APInt::getBitsSet(Op.getValueSizeInBits(),
+ N0.getValueSizeInBits(),
+ std::min(Op.getValueSizeInBits(),
+ VT.getSizeInBits()));
if (TruncatedBits == (KnownZero & TruncatedBits)) {
if (VT.bitsGT(Op.getValueType()))
return DAG.getNode(ISD::ZERO_EXTEND, N->getDebugLoc(), VT, Op);