[GlobalISel] Revise 'assignCustomValue' interface

llvm/include/llvm/CodeGen/GlobalISel/CallLowering.h

@@ -291,8 +291,8 @@ class CallLowering {
     /// \p If the handler wants the assignments to be delayed until after
     /// mem loc assignments, then it sets \p Thunk to the thunk to do the
     /// assignment.
-    /// \return The number of \p VAs that have been assigned after the first
-    ///         one, and which should therefore be skipped from further
+    /// \return The number of \p VAs that have been assigned including the
+    ///         first one, and which should therefore be skipped from further
     ///         processing.
     virtual unsigned assignCustomValue(ArgInfo &Arg, ArrayRef<CCValAssign> VAs,
                                        std::function<void()> *Thunk = nullptr) {

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

@@ -694,7 +694,7 @@ bool CallLowering::handleAssignments(ValueHandler &Handler,
         DelayedOutgoingRegAssignments.emplace_back(Thunk);
       if (!NumArgRegs)
         return false;
-      j += NumArgRegs;
+      j += (NumArgRegs - 1);
       continue;
     }
 

llvm/lib/Target/ARM/ARMCallLowering.cpp

@@ -166,11 +166,11 @@ struct ARMOutgoingValueHandler : public CallLowering::OutgoingValueHandler {
         assignValueToReg(NewRegs[0], VA.getLocReg(), VA);
         assignValueToReg(NewRegs[1], NextVA.getLocReg(), NextVA);
       };
-      return 1;
+      return 2;
     }
     assignValueToReg(NewRegs[0], VA.getLocReg(), VA);
     assignValueToReg(NewRegs[1], NextVA.getLocReg(), NextVA);
-    return 1;
+    return 2;
   }
 
   MachineInstrBuilder MIB;
@@ -341,7 +341,7 @@ struct ARMIncomingValueHandler : public CallLowering::IncomingValueHandler {
 
     MIRBuilder.buildMergeLikeInstr(Arg.Regs[0], NewRegs);
 
-    return 1;
+    return 2;
   }
 
   /// Marking a physical register as used is different between formal

llvm/lib/Target/Mips/MipsCallLowering.cpp

@@ -185,7 +185,7 @@ MipsIncomingValueHandler::assignCustomValue(CallLowering::ArgInfo &Arg,
 
   markPhysRegUsed(VALo.getLocReg());
   markPhysRegUsed(VAHi.getLocReg());
-  return 1;
+  return 2;
 }
 
 namespace {

llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp

@@ -146,11 +146,11 @@ struct RISCVOutgoingValueHandler : public CallLowering::OutgoingValueHandler {
 
     if (Thunk) {
       *Thunk = assignFunc;
-      return 1;
+      return 2;
     }
 
     assignFunc();
-    return 1;
+    return 2;
   }
 
 private:
@@ -266,7 +266,7 @@ struct RISCVIncomingValueHandler : public CallLowering::IncomingValueHandler {
 
     MIRBuilder.buildMergeLikeInstr(Arg.Regs[0], NewRegs);
 
-    return 1;
+    return 2;
   }
 
   /// How the physical register gets marked varies between formal