[llvm] [RISCV][GISEL] Legalize G_VAARG through expansion. (PR #73065)

[Craig Topper via llvm-commits]

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@@ -7868,6 +7870,59 @@ LegalizerHelper::lowerVectorReduction(MachineInstr &MI) {
   return UnableToLegalize;
 }
 
+static Type *getTypeForLLT(LLT Ty, LLVMContext &C);
+
+LegalizerHelper::LegalizeResult LegalizerHelper::lowerVAArg(MachineInstr &MI) {
+  MachineFunction &MF = *MI.getMF();
+  const DataLayout &DL = MIRBuilder.getDataLayout();
+  LLVMContext &Ctx = MF.getFunction().getContext();
+  Register ListPtr = MI.getOperand(1).getReg();
+  LLT PtrTy = MRI.getType(ListPtr);
+
+  // LstPtr is a pointer to the head of the list. Get the address
+  // of the head of the list.
+  Align PtrAlignment = DL.getABITypeAlign(getTypeForLLT(PtrTy, Ctx));
+  MachineMemOperand *PtrLoadMMO =
+      MF.getMachineMemOperand(MachinePointerInfo::getUnknownStack(MF),
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topperc wrote:

How do you knows its on the stack?

https://github.com/llvm/llvm-project/pull/73065