[llvm] [SystemZ] Handle IR struct arguments correctly. (PR #169583)

[Jonas Paulsson via llvm-commits]

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@@ -2074,16 +2096,26 @@ SDValue SystemZTargetLowering::LowerFormalArguments(
                                    MachinePointerInfo()));
       // If the original argument was split (e.g. i128), we need
       // to load all parts of it here (using the same address).
-      unsigned ArgIndex = Ins[I].OrigArgIndex;
-      assert (Ins[I].PartOffset == 0);
-      while (I + 1 != E && Ins[I + 1].OrigArgIndex == ArgIndex) {
-        CCValAssign &PartVA = ArgLocs[I + 1];
-        unsigned PartOffset = Ins[I + 1].PartOffset;
-        SDValue Address = DAG.getNode(ISD::ADD, DL, PtrVT, ArgValue,
-                                      DAG.getIntPtrConstant(PartOffset, DL));
-        InVals.push_back(DAG.getLoad(PartVA.getValVT(), DL, Chain, Address,
-                                     MachinePointerInfo()));
-        ++I;
+      MVT PartVT;
+      unsigned NumParts;
+      if (analyzeArgSplit(Ins, ArgLocs, I, PartVT, NumParts)) {
+        // TODO: It is strange that while LowerCallTo() sets the PartOffset
+        // relative to the first split part LowerArguments() sets the offset
+        // from the beginning of the struct. So with {i32, i256}, the
+        // PartOffset for the i256 parts are differently handled. Try to
+        // remove that difference and use PartOffset directly here (instead
+        // of SplitBaseOffs).
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JonPsson1 wrote:

Follow up: #170732

https://github.com/llvm/llvm-project/pull/169583