[clang] [llvm] Add AMO load with Compare and Swap Not Equal (PR #178061)

[via llvm-commits]

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@@ -11506,6 +11480,48 @@ SDValue PPCTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
   return Flags;
 }
 
+SDValue PPCTargetLowering::LowerINTRINSIC_W_CHAIN(SDValue Op,
+                                                  SelectionDAG &DAG) const {
+  unsigned IntrinsicID = Op.getConstantOperandVal(1);
+  SDLoc dl(Op);
+  switch (IntrinsicID) {
+  case Intrinsic::ppc_amo_lwat_csne:
+  case Intrinsic::ppc_amo_ldat_csne:
+    SDValue Chain = Op.getOperand(0);
+    SDValue Ptr = Op.getOperand(2);
+    SDValue CmpVal = Op.getOperand(3);
+    SDValue NewVal = Op.getOperand(4);
+
+    EVT VT = IntrinsicID == Intrinsic::ppc_amo_ldat_csne ? MVT::i64 : MVT::i32;
+    Type *Ty = VT.getTypeForEVT(*DAG.getContext());
+    Type *IntPtrTy = DAG.getDataLayout().getIntPtrType(*DAG.getContext());
+
+    TargetLowering::ArgListTy Args;
+    Args.emplace_back(DAG.getUNDEF(VT), Ty);
+    Args.emplace_back(CmpVal, Ty);
+    Args.emplace_back(NewVal, Ty);
+    Args.emplace_back(Ptr, IntPtrTy);
+
+    // Lower to dummy call to use ABI for consecutive register allocation.
+    // Places return value, compare value, and new value in X3/X4/X5 as required
+    // by lwat/ldat FC=16, avoiding a new register class for 3 adjacent
+    // registers.
+    const char *SymName = IntrinsicID == Intrinsic::ppc_amo_ldat_csne
+                              ? "__ldat_csne_dummy"
+                              : "__lwat_csne_dummy";
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RolandF77 wrote:

I think we should avoid terms like dummy in instructions that appear in traces. Maybe use pseudo or macro or something.

https://github.com/llvm/llvm-project/pull/178061