1 files changed, 33 insertions, 0 deletions
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index f692180..944a1e2 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -585,6 +585,10 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
   // We cannot sextinreg(i1).  Expand to shifts.
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
 
+  // Custom handling for PowerPC ucmp instruction
+  setOperationAction(ISD::UCMP, MVT::i32, Custom);
+  setOperationAction(ISD::UCMP, MVT::i64, isPPC64 ? Custom : Expand);
+
   // NOTE: EH_SJLJ_SETJMP/_LONGJMP supported here is NOT intended to support
   // SjLj exception handling but a light-weight setjmp/longjmp replacement to
   // support continuation, user-level threading, and etc.. As a result, no
@@ -12618,6 +12622,33 @@ SDValue PPCTargetLowering::LowerSSUBO(SDValue Op, SelectionDAG &DAG) const {
   return DAG.getMergeValues({Sub, OverflowTrunc}, dl);
 }
 
+// Lower unsigned 3-way compare producing -1/0/1.
+SDValue PPCTargetLowering::LowerUCMP(SDValue Op, SelectionDAG &DAG) const {
+  SDLoc DL(Op);
+  SDValue A = DAG.getFreeze(Op.getOperand(0));
+  SDValue B = DAG.getFreeze(Op.getOperand(1));
+  EVT OpVT = A.getValueType();   // operand type
+  EVT ResVT = Op.getValueType(); // result type
+
+  // First compute diff = A - B (will become subf).
+  SDValue Diff = DAG.getNode(ISD::SUB, DL, OpVT, A, B);
+
+  // Generate B - A using SUBC to capture carry.
+  SDVTList VTs = DAG.getVTList(OpVT, MVT::i32);
+  SDValue SubC = DAG.getNode(PPCISD::SUBC, DL, VTs, B, A);
+  SDValue CA0 = SubC.getValue(1);
+
+  // t2 = A - B + CA0 using SUBE.
+  SDValue SubE1 = DAG.getNode(PPCISD::SUBE, DL, VTs, A, B, CA0);
+  SDValue CA1 = SubE1.getValue(1);
+
+  // res = diff - t2 + CA1 using SUBE (produces desired -1/0/1).
+  SDValue ResPair = DAG.getNode(PPCISD::SUBE, DL, VTs, Diff, SubE1, CA1);
+
+  // Extract the first result and truncate to result type if needed
+  return DAG.getSExtOrTrunc(ResPair.getValue(0), DL, ResVT);
+}
+
 /// LowerOperation - Provide custom lowering hooks for some operations.
 ///
 SDValue PPCTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
@@ -12722,6 +12753,8 @@ SDValue PPCTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::UADDO_CARRY:
   case ISD::USUBO_CARRY:
     return LowerADDSUBO_CARRY(Op, DAG);
+  case ISD::UCMP:
+    return LowerUCMP(Op, DAG);
   }
 }