[llvm] [GISel][RISCV]Implement indirect parameter passing for large scalars (PR #95429)

[Gábor Spaits via llvm-commits]

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@@ -764,19 +765,28 @@ bool CallLowering::handleAssignments(ValueHandler &Handler,
       // If we can't directly assign the register, we need one or more
       // intermediate values.
       Args[i].Regs.resize(NumParts);
-
-      // For each split register, create and assign a vreg that will store
-      // the incoming component of the larger value. These will later be
-      // merged to form the final vreg.
-      for (unsigned Part = 0; Part < NumParts; ++Part)
-        Args[i].Regs[Part] = MRI.createGenericVirtualRegister(NewLLT);
+    
+      // When we have indirect parameter passing we are receiving a pointer,
+      // that points to the actual value. In that case we need a pointer.
+      if (VA.getLocInfo() == CCValAssign::Indirect &&
+          Args[i].Flags[0].isSplit()) {
+        if (Handler.isIncomingArgumentHandler())
+          Args[i].Regs[0] = MRI.createGenericVirtualRegister(PointerTy);
+      } else {
+        // For each split register, create and assign a vreg that will store
+        // the incoming component of the larger value. These will later be
+        // merged to form the final vreg.
+        for (unsigned Part = 0; Part < NumParts; ++Part)
+          Args[i].Regs[Part] = MRI.createGenericVirtualRegister(NewLLT);
+      }
     }
 
     assert((j + (NumParts - 1)) < ArgLocs.size() &&
            "Too many regs for number of args");
 
     // Coerce into outgoing value types before register assignment.
-    if (!Handler.isIncomingArgumentHandler() && OrigTy != ValTy) {
+    if (!Handler.isIncomingArgumentHandler() && OrigTy != ValTy &&
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spaits wrote:

Because when passing the value, from the callers point of view, the preparation of the call (like putting the arguments in the right register) an outgoing value handler is used and and outgoing value can also be considered indirect. That case is handled later on the code.  

https://github.com/llvm/llvm-project/pull/95429