diff --git a/src/cmd/compile/internal/amd64/ssa.go b/src/cmd/compile/internal/amd64/ssa.go
index 42c12953f9..38d2d43e27 100644
--- a/src/cmd/compile/internal/amd64/ssa.go
+++ b/src/cmd/compile/internal/amd64/ssa.go
@@ -989,9 +989,9 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		// The loop only runs once.
 		for _, ap := range v.Block.Func.RegArgs {
 			// Pass the spill/unspill information along to the assembler, offset by size of return PC pushed on stack.
-			addr := ssagen.SpillSlotAddr(ap.Mem(), x86.REG_SP, v.Block.Func.Config.PtrSize)
+			addr := ssagen.SpillSlotAddr(ap, x86.REG_SP, v.Block.Func.Config.PtrSize)
 			s.FuncInfo().AddSpill(
-				obj.RegSpill{Reg: ap.Reg(), Addr: addr, Unspill: loadByType(ap.Type()), Spill: storeByType(ap.Type())})
+				obj.RegSpill{Reg: ap.Reg, Addr: addr, Unspill: loadByType(ap.Type), Spill: storeByType(ap.Type)})
 		}
 		v.Block.Func.RegArgs = nil
 		ssagen.CheckArgReg(v)
diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go
index 819d7573d6..378a73a95a 100644
--- a/src/cmd/compile/internal/ssa/func.go
+++ b/src/cmd/compile/internal/ssa/func.go
@@ -64,7 +64,7 @@ type Func struct {
 	Names []LocalSlot
 
 	// RegArgs is a slice of register-memory pairs that must be spilled and unspilled in the uncommon path of function entry.
-	RegArgs []ArgPair
+	RegArgs []Spill
 	// AuxCall describing parameters and results for this function.
 	OwnAux *AuxCall
 
diff --git a/src/cmd/compile/internal/ssa/location.go b/src/cmd/compile/internal/ssa/location.go
index af0a913d17..252c47cdeb 100644
--- a/src/cmd/compile/internal/ssa/location.go
+++ b/src/cmd/compile/internal/ssa/location.go
@@ -102,28 +102,8 @@ func (t LocResults) String() string {
 	return a
 }
 
-type ArgPair struct {
-	reg *Register
-	mem LocalSlot
-}
-
-func (ap *ArgPair) Reg() int16 {
-	return ap.reg.objNum
-}
-
-func (ap *ArgPair) Type() *types.Type {
-	return ap.mem.Type
-}
-
-func (ap *ArgPair) Mem() *LocalSlot {
-	return &ap.mem
-}
-
-func (t ArgPair) String() string {
-	n0 := "nil"
-	if t.reg != nil {
-		n0 = t.reg.String()
-	}
-	n1 := t.mem.String()
-	return fmt.Sprintf("<%s,%s>", n0, n1)
+type Spill struct {
+	Type   *types.Type
+	Offset int64
+	Reg    int16
 }
diff --git a/src/cmd/compile/internal/ssa/stackalloc.go b/src/cmd/compile/internal/ssa/stackalloc.go
index 45058d4e72..8fe18e5f02 100644
--- a/src/cmd/compile/internal/ssa/stackalloc.go
+++ b/src/cmd/compile/internal/ssa/stackalloc.go
@@ -165,15 +165,6 @@ func (s *stackAllocState) stackalloc() {
 			f.setHome(v, loc)
 			continue
 		}
-
-		nameOff := v.Aux.(*AuxNameOffset)
-		loc := LocalSlot{N: nameOff.Name, Type: v.Type, Off: nameOff.Offset}
-		if f.pass.debug > stackDebug {
-			fmt.Printf("stackalloc Op%s %s to %s\n", v.Op, v, loc)
-		}
-		// register args already allocated to registers, but need to know the stack allocation for later
-		reg := f.getHome(v.ID).(*Register)
-		f.RegArgs = append(f.RegArgs, ArgPair{reg: reg, mem: loc})
 	}
 
 	// For each type, we keep track of all the stack slots we
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index f0bce0756a..e7d4865375 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -641,6 +641,22 @@ func buildssa(fn *ir.Func, worker int) *ssa.Func {
 		s.emitOpenDeferInfo()
 	}
 
+	// Record incoming parameter spill information for morestack calls emitted in the assembler.
+	// This is done here, using all the parameters (used, partially used, and unused) because
+	// it mimics the behavior of the former ABI (everything stored) and because it's not 100%
+	// clear if naming conventions are respected in autogenerated code.
+	// TODO figure out exactly what's unused, don't spill it. Make liveness fine-grained, also.
+	// TODO non-amd64 architectures have link registers etc that may require adjustment here.
+	for _, p := range params.InParams() {
+		typs, offs := p.RegisterTypesAndOffsets()
+		for i, t := range typs {
+			o := offs[i]                // offset within parameter
+			fo := p.FrameOffset(params) // offset of parameter in frame
+			reg := ssa.ObjRegForAbiReg(p.Registers[i], s.f.Config)
+			s.f.RegArgs = append(s.f.RegArgs, ssa.Spill{Reg: reg, Offset: fo + o, Type: t})
+		}
+	}
+
 	return s.f
 }
 
@@ -7578,16 +7594,12 @@ func deferstruct(stksize int64) *types.Type {
 // The resulting addr is used in a non-standard context -- in the prologue
 // of a function, before the frame has been constructed, so the standard
 // addressing for the parameters will be wrong.
-func SpillSlotAddr(slot *ssa.LocalSlot, baseReg int16, extraOffset int64) obj.Addr {
-	n, off := slot.N, slot.Off
-	if n.Class != ir.PPARAM && n.Class != ir.PPARAMOUT {
-		panic("Only expected to see param and returns here")
-	}
+func SpillSlotAddr(spill ssa.Spill, baseReg int16, extraOffset int64) obj.Addr {
 	return obj.Addr{
 		Name:   obj.NAME_NONE,
 		Type:   obj.TYPE_MEM,
 		Reg:    baseReg,
-		Offset: off + extraOffset + n.FrameOffset(),
+		Offset: spill.Offset + extraOffset,
 	}
 }