cmd/compile: test register ABI for method, interface, closure calls

This is enabled with a ridiculous magic name for method,
or for last input type passed, that needs to be changed
to something inutterable before actual release.

Ridiculous method name: MagicMethodNameForTestingRegisterABI
Ridiculous last (input) type name: MagicLastTypeNameForTestingRegisterABI

RLTN is tested with strings.Contains, so you can have
MagicLastTypeNameForTestingRegisterABI1
and
MagicLastTypeNameForTestingRegisterABI2
if that is helpful

Includes test test/abi/fibish2.go

Updates #44816.

Change-Id: I592a6edc71ca9bebdd1d00e24edee1ceebb3e43f
Reviewed-on: https://go-review.googlesource.com/c/go/+/299410
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/ssa/expand_calls.go

@@ -386,41 +386,34 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 		which := selector.AuxInt
 		if which == aux.NResults() { // mem is after the results.
 			// rewrite v as a Copy of call -- the replacement call will produce a mem.
-			if call.Op == OpStaticLECall {
-				if leaf != selector {
-					panic("Unexpected selector of memory")
-				}
-				// StaticCall selector will address last element of Result.
-				// TODO do this for all the other call types eventually.
-				if aux.abiInfo == nil {
-					panic(badVal("aux.abiInfo nil for call", call))
-				}
-				if existing := x.memForCall[call.ID]; existing == nil {
-					selector.AuxInt = int64(aux.abiInfo.OutRegistersUsed())
-					x.memForCall[call.ID] = selector
-				} else {
-					selector.copyOf(existing)
-				}
-			} else {
-				leaf.copyOf(call)
+			if leaf != selector {
+				panic("Unexpected selector of memory")
 			}
+			if aux.abiInfo == nil {
+				panic(badVal("aux.abiInfo nil for call", call))
+			}
+			if existing := x.memForCall[call.ID]; existing == nil {
+				selector.AuxInt = int64(aux.abiInfo.OutRegistersUsed())
+				x.memForCall[call.ID] = selector
+			} else {
+				selector.copyOf(existing)
+			}
+
 		} else {
 			leafType := removeTrivialWrapperTypes(leaf.Type)
 			if x.canSSAType(leafType) {
 				pt := types.NewPtr(leafType)
 				// Any selection right out of the arg area/registers has to be same Block as call, use call as mem input.
-				if call.Op == OpStaticLECall { // TODO this is temporary until all calls are register-able
-					// Create a "mem" for any loads that need to occur.
-					if mem := x.memForCall[call.ID]; mem != nil {
-						if mem.Block != call.Block {
-							panic(fmt.Errorf("selector and call need to be in same block, selector=%s; call=%s", selector.LongString(), call.LongString()))
-						}
-						call = mem
-					} else {
-						mem = call.Block.NewValue1I(call.Pos.WithNotStmt(), OpSelectN, types.TypeMem, int64(aux.abiInfo.OutRegistersUsed()), call)
-						x.memForCall[call.ID] = mem
-						call = mem
+				// Create a "mem" for any loads that need to occur.
+				if mem := x.memForCall[call.ID]; mem != nil {
+					if mem.Block != call.Block {
+						panic(fmt.Errorf("selector and call need to be in same block, selector=%s; call=%s", selector.LongString(), call.LongString()))
 					}
+					call = mem
+				} else {
+					mem = call.Block.NewValue1I(call.Pos.WithNotStmt(), OpSelectN, types.TypeMem, int64(aux.abiInfo.OutRegistersUsed()), call)
+					x.memForCall[call.ID] = mem
+					call = mem
 				}
 				outParam := aux.abiInfo.OutParam(int(which))
 				if len(outParam.Registers) > 0 {
@@ -1350,14 +1343,15 @@ func expandCalls(f *Func) {
 			case OpStaticLECall:
 				v.Op = OpStaticCall
 				rts := abi.RegisterTypes(v.Aux.(*AuxCall).abiInfo.OutParams())
-				// TODO need to insert all the register types.
 				v.Type = types.NewResults(append(rts, types.TypeMem))
 			case OpClosureLECall:
 				v.Op = OpClosureCall
-				v.Type = types.TypeMem
+				rts := abi.RegisterTypes(v.Aux.(*AuxCall).abiInfo.OutParams())
+				v.Type = types.NewResults(append(rts, types.TypeMem))
 			case OpInterLECall:
 				v.Op = OpInterCall
-				v.Type = types.TypeMem
+				rts := abi.RegisterTypes(v.Aux.(*AuxCall).abiInfo.OutParams())
+				v.Type = types.NewResults(append(rts, types.TypeMem))
 			}
 		}
 	}

src/cmd/compile/internal/ssa/gen/AMD64Ops.go

@@ -775,10 +775,10 @@ func init() {
 			faultOnNilArg0: true,
 		},
 
-		// With a register ABI, the actual register info for these instructions (i.e., what is used in regalloc) is augmented with per-call-site bindings of additional arguments to specific registers.
-		{name: "CALLstatic", argLength: -1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                             // call static function aux.(*obj.LSym).  arg0=mem, auxint=argsize, returns mem
-		{name: "CALLclosure", argLength: 3, reg: regInfo{inputs: []regMask{gpsp, buildReg("DX"), 0}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true}, // call function via closure.  arg0=codeptr, arg1=closure, arg2=mem, auxint=argsize, returns mem
-		{name: "CALLinter", argLength: 2, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                        // call fn by pointer.  arg0=codeptr, arg1=mem, auxint=argsize, returns mem
+		// With a register ABI, the actual register info for these instructions (i.e., what is used in regalloc) is augmented with per-call-site bindings of additional arguments to specific in and out registers.
+		{name: "CALLstatic", argLength: -1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                              // call static function aux.(*obj.LSym).  last arg=mem, auxint=argsize, returns mem
+		{name: "CALLclosure", argLength: -1, reg: regInfo{inputs: []regMask{gpsp, buildReg("DX"), 0}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true}, // call function via closure.  arg0=codeptr, arg1=closure, last arg=mem, auxint=argsize, returns mem
+		{name: "CALLinter", argLength: -1, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                        // call fn by pointer.  arg0=codeptr, last arg=mem, auxint=argsize, returns mem
 
 		// arg0 = destination pointer
 		// arg1 = source pointer

src/cmd/compile/internal/ssa/gen/genericOps.go

@@ -264,7 +264,7 @@ var genericOps = []opData{
 	//   ±0  → ±0 (sign preserved)
 	//   x<0 → NaN
 	//   NaN → NaN
-	{name: "Sqrt", argLength: 1}, // √arg0   (floating point, double precision)
+	{name: "Sqrt", argLength: 1},   // √arg0   (floating point, double precision)
 	{name: "Sqrt32", argLength: 1}, // √arg0 (floating point, single precision)
 
 	// Round to integer, float64 only.
@@ -396,9 +396,28 @@ var genericOps = []opData{
 	// TODO(josharian): ClosureCall and InterCall should have Int32 aux
 	// to match StaticCall's 32 bit arg size limit.
 	// TODO(drchase,josharian): could the arg size limit be bundled into the rules for CallOff?
-	{name: "ClosureCall", argLength: 3, aux: "CallOff", call: true},    // arg0=code pointer, arg1=context ptr, arg2=memory.  auxint=arg size.  Returns memory.
-	{name: "StaticCall", argLength: -1, aux: "CallOff", call: true},    // call function aux.(*obj.LSym), arg0..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
-	{name: "InterCall", argLength: 2, aux: "CallOff", call: true},      // interface call.  arg0=code pointer, arg1=memory, auxint=arg size.  Returns memory.
+
+	// Before lowering, LECalls receive their fixed inputs (first), memory (last),
+	// and a variable number of input values in the middle.
+	// They produce a variable number of result values.
+	// These values are not necessarily "SSA-able"; they can be too large,
+	// but in that case inputs are loaded immediately before with OpDereference,
+	// and outputs are stored immediately with OpStore.
+	//
+	// After call expansion, Calls have the same fixed-middle-memory arrangement of inputs,
+	// with the difference that the "middle" is only the register-resident inputs,
+	// and the non-register inputs are instead stored at ABI-defined offsets from SP
+	// (and the stores thread through the memory that is ultimately an input to the call).
+	// Outputs follow a similar pattern; register-resident outputs are the leading elements
+	// of a Result-typed output, with memory last, and any memory-resident outputs have been
+	// stored to ABI-defined locations.  Each non-memory input or output fits in a register.
+	//
+	// Subsequent architecture-specific lowering only changes the opcode.
+
+	{name: "ClosureCall", argLength: -1, aux: "CallOff", call: true}, // arg0=code pointer, arg1=context ptr, arg2..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
+	{name: "StaticCall", argLength: -1, aux: "CallOff", call: true},  // call function aux.(*obj.LSym), arg0..argN-1 are register inputs, argN=memory.  auxint=arg size.  Returns Result of register results, plus memory.
+	{name: "InterCall", argLength: -1, aux: "CallOff", call: true},   // interface call.  arg0=code pointer, arg1..argN-1 are register inputs, argN=memory, auxint=arg size.  Returns Result of register results, plus memory.
+
 	{name: "ClosureLECall", argLength: -1, aux: "CallOff", call: true}, // late-expanded closure call. arg0=code pointer, arg1=context ptr,  arg2..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 	{name: "StaticLECall", argLength: -1, aux: "CallOff", call: true},  // late-expanded static call function aux.(*ssa.AuxCall.Fn). arg0..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 	{name: "InterLECall", argLength: -1, aux: "CallOff", call: true},   // late-expanded interface call. arg0=code pointer, arg1..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.

src/cmd/compile/internal/ssa/op.go

@@ -10,6 +10,7 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"fmt"
+	"strings"
 )
 
 // An Op encodes the specific operation that a Value performs.
@@ -68,6 +69,27 @@ type regInfo struct {
 	outputs []outputInfo
 }
 
+func (r *regInfo) String() string {
+	s := ""
+	s += "INS:\n"
+	for _, i := range r.inputs {
+		mask := fmt.Sprintf("%64b", i.regs)
+		mask = strings.Replace(mask, "0", ".", -1)
+		s += fmt.Sprintf("%2d |%s|\n", i.idx, mask)
+	}
+	s += "OUTS:\n"
+	for _, i := range r.outputs {
+		mask := fmt.Sprintf("%64b", i.regs)
+		mask = strings.Replace(mask, "0", ".", -1)
+		s += fmt.Sprintf("%2d |%s|\n", i.idx, mask)
+	}
+	s += "CLOBBERS:\n"
+	mask := fmt.Sprintf("%64b", r.clobbers)
+	mask = strings.Replace(mask, "0", ".", -1)
+	s += fmt.Sprintf("   |%s|\n", mask)
+	return s
+}
+
 type auxType int8
 
 type Param struct {
@@ -116,20 +138,25 @@ func (a *AuxCall) Reg(i *regInfo, c *Config) *regInfo {
 		a.reg = i
 		return a.reg
 	}
-	a.reg.inputs = append(a.reg.inputs, i.inputs...)
+
+	k := len(i.inputs)
 	for _, p := range a.abiInfo.InParams() {
 		for _, r := range p.Registers {
 			m := archRegForAbiReg(r, c)
-			a.reg.inputs = append(a.reg.inputs, inputInfo{idx: len(a.reg.inputs), regs: (1 << m)})
+			a.reg.inputs = append(a.reg.inputs, inputInfo{idx: k, regs: (1 << m)})
+			k++
 		}
 	}
-	a.reg.outputs = append(a.reg.outputs, i.outputs...)
+	a.reg.inputs = append(a.reg.inputs, i.inputs...) // These are less constrained, thus should come last
+	k = len(i.outputs)
 	for _, p := range a.abiInfo.OutParams() {
 		for _, r := range p.Registers {
 			m := archRegForAbiReg(r, c)
-			a.reg.outputs = append(a.reg.outputs, outputInfo{idx: len(a.reg.outputs), regs: (1 << m)})
+			a.reg.outputs = append(a.reg.outputs, outputInfo{idx: k, regs: (1 << m)})
+			k++
 		}
 	}
+	a.reg.outputs = append(a.reg.outputs, i.outputs...)
 	a.reg.clobbers = i.clobbers
 	return a.reg
 }
@@ -299,12 +326,20 @@ func StaticAuxCall(sym *obj.LSym, args []Param, results []Param, paramResultInfo
 
 // InterfaceAuxCall returns an AuxCall for an interface call.
 func InterfaceAuxCall(args []Param, results []Param, paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
-	return &AuxCall{Fn: nil, args: args, results: results, abiInfo: paramResultInfo}
+	var reg *regInfo
+	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
+		reg = &regInfo{}
+	}
+	return &AuxCall{Fn: nil, args: args, results: results, abiInfo: paramResultInfo, reg: reg}
 }
 
 // ClosureAuxCall returns an AuxCall for a closure call.
 func ClosureAuxCall(args []Param, results []Param, paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
-	return &AuxCall{Fn: nil, args: args, results: results, abiInfo: paramResultInfo}
+	var reg *regInfo
+	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
+		reg = &regInfo{}
+	}
+	return &AuxCall{Fn: nil, args: args, results: results, abiInfo: paramResultInfo, reg: reg}
 }
 
 func (*AuxCall) CanBeAnSSAAux() {}

src/cmd/compile/internal/ssa/opGen.go

@@ -13275,7 +13275,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:         "CALLclosure",
 		auxType:      auxCallOff,
-		argLen:       3,
+		argLen:       -1,
 		clobberFlags: true,
 		call:         true,
 		reg: regInfo{
@@ -13289,7 +13289,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:         "CALLinter",
 		auxType:      auxCallOff,
-		argLen:       2,
+		argLen:       -1,
 		clobberFlags: true,
 		call:         true,
 		reg: regInfo{
@@ -35596,7 +35596,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:    "ClosureCall",
 		auxType: auxCallOff,
-		argLen:  3,
+		argLen:  -1,
 		call:    true,
 		generic: true,
 	},
@@ -35610,7 +35610,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:    "InterCall",
 		auxType: auxCallOff,
-		argLen:  2,
+		argLen:  -1,
 		call:    true,
 		generic: true,
 	},

src/cmd/compile/internal/ssagen/ssa.go

@@ -217,6 +217,10 @@ func AbiForFunc(fn *ir.Func) *abi.ABIConfig {
 	return abiForFunc(fn, ssaConfig.ABI0, ssaConfig.ABI1).Copy() // No idea what races will result, be safe
 }
 
+// TODO (NLT 2021-04-15) This must be changed to a name that cannot match; it may be helpful to other register ABI work to keep the trigger-logic
+const magicNameDotSuffix = ".MagicMethodNameForTestingRegisterABI"
+const magicLastTypeName = "MagicLastTypeNameForTestingRegisterABI"
+
 // abiForFunc implements ABI policy for a function, but does not return a copy of the ABI.
 // Passing a nil function returns ABIInternal.
 func abiForFunc(fn *ir.Func, abi0, abi1 *abi.ABIConfig) *abi.ABIConfig {
@@ -224,16 +228,38 @@ func abiForFunc(fn *ir.Func, abi0, abi1 *abi.ABIConfig) *abi.ABIConfig {
 	if !regabiEnabledForAllCompilation() {
 		a = abi0
 	}
-	if fn != nil && fn.Pragma&ir.RegisterParams != 0 { // TODO(register args) remove after register abi is working
+
+	if fn != nil {
 		name := ir.FuncName(fn)
-		if strings.Contains(name, ".") {
-			base.ErrorfAt(fn.Pos(), "Calls to //go:registerparams method %s won't work, remove the pragma from the declaration.", name)
+		magicName := strings.HasSuffix(name, magicNameDotSuffix)
+		if fn.Pragma&ir.RegisterParams != 0 { // TODO(register args) remove after register abi is working
+			if strings.Contains(name, ".") {
+				if !magicName {
+					base.ErrorfAt(fn.Pos(), "Calls to //go:registerparams method %s won't work, remove the pragma from the declaration.", name)
+				}
+			}
+			a = abi1
+		} else if magicName {
+			if base.FmtPos(fn.Pos()) == "<autogenerated>:1" {
+				// no way to put a pragma here, and it will error out in the real source code if they did not do it there.
+				a = abi1
+			} else {
+				base.ErrorfAt(fn.Pos(), "Methods with magic name %s (method %s) must also specify //go:registerparams", magicNameDotSuffix[1:], name)
+			}
+		}
+		if regAbiForFuncType(fn.Type().FuncType()) {
+			// fmt.Printf("Saw magic last type name for function %s\n", name)
+			a = abi1
 		}
-		a = abi1
 	}
 	return a
 }
 
+func regAbiForFuncType(ft *types.Func) bool {
+	np := ft.Params.NumFields()
+	return np > 0 && strings.Contains(ft.Params.FieldType(np-1).String(), magicLastTypeName)
+}
+
 func regabiEnabledForAllCompilation() bool {
 	// TODO compiler does not yet change behavior for GOEXPERIMENT=regabi
 	return false && objabi.Regabi_enabled != 0
@@ -4863,6 +4889,22 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 	var callArgs []*ssa.Value // For late-expansion, the args themselves (not stored, args to the call instead).
 	inRegisters := false
 
+	var magicFnNameSym *types.Sym
+	if fn.Name() != nil {
+		magicFnNameSym = fn.Name().Sym()
+		ss := magicFnNameSym.Name
+		if strings.HasSuffix(ss, magicNameDotSuffix) {
+			inRegisters = true
+		}
+	}
+	if magicFnNameSym == nil && n.Op() == ir.OCALLINTER {
+		magicFnNameSym = fn.(*ir.SelectorExpr).Sym()
+		ss := magicFnNameSym.Name
+		if strings.HasSuffix(ss, magicNameDotSuffix[1:]) {
+			inRegisters = true
+		}
+	}
+
 	switch n.Op() {
 	case ir.OCALLFUNC:
 		if k == callNormal && fn.Op() == ir.ONAME && fn.(*ir.Name).Class == ir.PFUNC {
@@ -4871,7 +4913,7 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 			// TODO(register args) remove after register abi is working
 			inRegistersImported := fn.Pragma()&ir.RegisterParams != 0
 			inRegistersSamePackage := fn.Func != nil && fn.Func.Pragma&ir.RegisterParams != 0
-			inRegisters = inRegistersImported || inRegistersSamePackage
+			inRegisters = inRegisters || inRegistersImported || inRegistersSamePackage
 			break
 		}
 		closure = s.expr(fn)
@@ -4898,6 +4940,11 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 	types.CalcSize(fn.Type())
 	stksize := fn.Type().ArgWidth() // includes receiver, args, and results
 
+	if regAbiForFuncType(n.X.Type().FuncType()) {
+		// fmt.Printf("Saw magic last type in call %v\n", n)
+		inRegisters = true
+	}
+
 	callABI := s.f.ABI1
 	if !inRegisters {
 		callABI = s.f.ABI0
@@ -5047,11 +5094,11 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 			// critical that we not clobber any arguments already
 			// stored onto the stack.
 			codeptr = s.rawLoad(types.Types[types.TUINTPTR], closure)
-			aux := ssa.ClosureAuxCall(ACArgs, ACResults, s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
+			aux := ssa.ClosureAuxCall(ACArgs, ACResults, callABI.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
 			call = s.newValue2A(ssa.OpClosureLECall, aux.LateExpansionResultType(), aux, codeptr, closure)
 		case codeptr != nil:
 			// Note that the "receiver" parameter is nil because the actual receiver is the first input parameter.
-			aux := ssa.InterfaceAuxCall(ACArgs, ACResults, s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
+			aux := ssa.InterfaceAuxCall(ACArgs, ACResults, params)
 			call = s.newValue1A(ssa.OpInterLECall, aux.LateExpansionResultType(), aux, codeptr)
 		case callee != nil:
 			aux := ssa.StaticAuxCall(callTargetLSym(callee, s.curfn.LSym), ACArgs, ACResults, params)

test/abi/fibish2.go

@@ -0,0 +1,40 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+// Test that register results are correctly returned (and passed)
+
+type MagicLastTypeNameForTestingRegisterABI func(int,MagicLastTypeNameForTestingRegisterABI) int
+
+//go:registerparams
+//go:noinline
+func minus(decrement int) MagicLastTypeNameForTestingRegisterABI {
+	return MagicLastTypeNameForTestingRegisterABI( func(x int, _ MagicLastTypeNameForTestingRegisterABI) int { return x-decrement} )
+}
+
+//go:noinline
+func f(x int, sub1 MagicLastTypeNameForTestingRegisterABI) (int, int) {
+
+	if x < 3 {
+		return 0, x
+	}
+
+	a, b := f(sub1(sub1(x, sub1), sub1), sub1)
+	c, d := f(sub1(x, sub1), sub1)
+	return a + d, b + c
+}
+
+func main() {
+	x := 40
+	a, b := f(x, minus(1))
+	fmt.Printf("f(%d)=%d,%d\n", x, a, b)
+}

test/abi/fibish2.out

@@ -0,0 +1 @@
+f(40)=39088169,126491972

test/abi/fibish_closure.go

@@ -0,0 +1,34 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+// Test that register results are correctly returned (and passed)
+
+type MagicLastTypeNameForTestingRegisterABI func(int, MagicLastTypeNameForTestingRegisterABI) (int, int)
+
+//go:noinline
+func f(x int, unused MagicLastTypeNameForTestingRegisterABI) (int, int) {
+
+	if x < 3 {
+		return 0, x
+	}
+
+	a, b := f(x-2, unused)
+	c, d := f(x-1, unused)
+	return a + d, b + c
+}
+
+func main() {
+	x := 40
+	a, b := f(x, f)
+	fmt.Printf("f(%d)=%d,%d\n", x, a, b)
+}

test/abi/fibish_closure.out

@@ -0,0 +1 @@
+f(40)=39088169,126491972

test/abi/methods.go

@@ -0,0 +1,51 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type toobig struct {
+	a,b,c string
+}
+
+//go:registerparams
+//go:noinline
+func (x *toobig) MagicMethodNameForTestingRegisterABI(y toobig, z toobig) toobig {
+	return toobig{x.a, y.b, z.c}
+}
+
+type AnInterface interface {
+	MagicMethodNameForTestingRegisterABI(y toobig, z toobig) toobig
+}
+
+//go:registerparams
+//go:noinline
+func I(a,b,c string) toobig {
+	return toobig{a,b,c}
+}
+
+// AnIid prevents the compiler from figuring out what the interface really is.
+//go:noinline
+func AnIid(x AnInterface) AnInterface {
+	return x
+}
+
+var tmp toobig
+func main() {
+	x := I("Ahoy", "1,", "2")
+	y := I("3", "there,", "4")
+	z := I("5", "6,", "Matey")
+	tmp = x.MagicMethodNameForTestingRegisterABI(y,z)
+	fmt.Println(tmp.a, tmp.b, tmp.c)
+	tmp = AnIid(&x).MagicMethodNameForTestingRegisterABI(y,z)
+	fmt.Println(tmp.a, tmp.b, tmp.c)
+}

test/abi/methods.out

@@ -0,0 +1,2 @@
+Ahoy there, Matey
+Ahoy there, Matey