[llvm] [GlobalISel][RISCV] SelectionDAG like indirect parameter passing (PR #216724)

[Craig Topper via llvm-commits]

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@@ -859,25 +846,44 @@ bool CallLowering::handleAssignments(ValueHandler &Handler,
     // Now split the registers into the assigned types.
     Args[i].OrigRegs.assign(Args[i].Regs.begin(), Args[i].Regs.end());
 
+    int IndirectFrameIdx = 0;
+    Register IndirectPointerToStackReg{};
+    TypeSize CurrentIndirectChunkSize = TypeSize::getZero();
+    for (unsigned Part = 0; Part < NumParts; Part++) {
+      if (ArgLocs[j + Part].getLocInfo() == CCValAssign::Indirect)
+        CurrentIndirectChunkSize += ArgLocs[j + Part].getValVT().getStoreSize();
+      else if (CurrentIndirectChunkSize != 0)
+        llvm_unreachable("Indirect parameter passing where the middle part of "
+                         "a parameter is indirect isn't yet supported!");
+    }
+
     if (NumParts != 1 || NewLLT != OrigTy) {
-      // If we can't directly assign the register, we need one or more
-      // intermediate values.
-      Args[i].Regs.resize(NumParts);
-
-      // When we have indirect parameter passing we are receiving a pointer,
-      // that points to the actual value, so we need one "temporary" pointer.
-      if (VA.getLocInfo() == CCValAssign::Indirect) {
-        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);
+      Args[i].Regs.clear();
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topperc wrote:

The loop here always pushs NumParts times. I was wondering if we could allocate NumParts entries after the clear. This way each push_back in th e loop doesn't need to check for if the vector needs to be resized.

https://github.com/llvm/llvm-project/pull/216724