cmd/compile: change StaticCall to return a "Results"

StaticLECall (multiple value in +mem, multiple value result +mem) ->
StaticCall (multiple ergister value in +mem,
   multiple register-sized-value result +mem) ->
ARCH CallStatic (multiple ergister value in +mem,
   multiple register-sized-value result +mem)

But the architecture-dependent stuff is indifferent to whether
it is mem->mem or (mem)->(mem) until Prog generation.

Deal with OpSelectN -> Prog in ssagen/ssa.go, others, as they
appear.

For #40724.

Change-Id: I1d0436f6371054f1881862641d8e7e418e4a6a16
Reviewed-on: https://go-review.googlesource.com/c/go/+/293391
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>

18 files changed, 387 insertions, 382 deletions

diff --git a/src/cmd/compile/internal/abi/abiutils.go b/src/cmd/compile/internal/abi/abiutils.go
index 4bd27efb59..b43d95e976 100644
--- a/src/cmd/compile/internal/abi/abiutils.go
+++ b/src/cmd/compile/internal/abi/abiutils.go
@@ -27,6 +27,8 @@ type ABIParamResultInfo struct {
 	outparams         []ABIParamAssignment
 	offsetToSpillArea int64
 	spillAreaSize     int64
+	inRegistersUsed   int
+	outRegistersUsed  int
 	config            *ABIConfig // to enable String() method
 }
 
@@ -42,6 +44,14 @@ func (a *ABIParamResultInfo) OutParams() []ABIParamAssignment {
 	return a.outparams
 }
 
+func (a *ABIParamResultInfo) InRegistersUsed() int {
+	return a.inRegistersUsed
+}
+
+func (a *ABIParamResultInfo) OutRegistersUsed() int {
+	return a.outRegistersUsed
+}
+
 func (a *ABIParamResultInfo) InParam(i int) ABIParamAssignment {
 	return a.inparams[i]
 }
@@ -164,6 +174,55 @@ func (a *ABIConfig) NumParamRegs(t *types.Type) int {
 	return n
 }
 
+// preAllocateParams gets the slice sizes right for inputs and outputs.
+func (a *ABIParamResultInfo) preAllocateParams(hasRcvr bool, nIns, nOuts int) {
+	if hasRcvr {
+		nIns++
+	}
+	a.inparams = make([]ABIParamAssignment, 0, nIns)
+	a.outparams = make([]ABIParamAssignment, 0, nOuts)
+}
+
+// ABIAnalyzeTypes takes an optional receiver type, arrays of ins and outs, and returns an ABIParamResultInfo,
+// based on the given configuration.  This is the same result computed by config.ABIAnalyze applied to the
+// corresponding method/function type, except that all the embedded parameter names are nil.
+// This is intended for use by ssagen/ssa.go:(*state).rtcall, for runtime functions that lack a parsed function type.
+func (config *ABIConfig) ABIAnalyzeTypes(rcvr *types.Type, ins, outs []*types.Type) *ABIParamResultInfo {
+	setup()
+	s := assignState{
+		rTotal: config.regAmounts,
+	}
+	result := &ABIParamResultInfo{config: config}
+	result.preAllocateParams(rcvr != nil, len(ins), len(outs))
+
+	// Receiver
+	if rcvr != nil {
+		result.inparams = append(result.inparams,
+			s.assignParamOrReturn(rcvr, nil, false))
+	}
+
+	// Inputs
+	for _, t := range ins {
+		result.inparams = append(result.inparams,
+			s.assignParamOrReturn(t, nil, false))
+	}
+	s.stackOffset = types.Rnd(s.stackOffset, int64(types.RegSize))
+	result.inRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
+
+	// Outputs
+	s.rUsed = RegAmounts{}
+	for _, t := range outs {
+		result.outparams = append(result.outparams, s.assignParamOrReturn(t, nil, true))
+	}
+	// The spill area is at a register-aligned offset and its size is rounded up to a register alignment.
+	// TODO in theory could align offset only to minimum required by spilled data types.
+	result.offsetToSpillArea = alignTo(s.stackOffset, types.RegSize)
+	result.spillAreaSize = alignTo(s.spillOffset, types.RegSize)
+	result.outRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
+
+	return result
+}
+
 // ABIAnalyze takes a function type 't' and an ABI rules description
 // 'config' and analyzes the function to determine how its parameters
 // and results will be passed (in registers or on the stack), returning
@@ -174,33 +233,37 @@ func (config *ABIConfig) ABIAnalyze(t *types.Type) *ABIParamResultInfo {
 		rTotal: config.regAmounts,
 	}
 	result := &ABIParamResultInfo{config: config}
+	ft := t.FuncType()
+	result.preAllocateParams(t.NumRecvs() != 0, ft.Params.NumFields(), ft.Results.NumFields())
 
 	// Receiver
-	ft := t.FuncType()
+	// TODO(register args) ? seems like "struct" and "fields" is not right anymore for describing function parameters
 	if t.NumRecvs() != 0 {
-		rfsl := ft.Receiver.FieldSlice()
+		r := ft.Receiver.FieldSlice()[0]
 		result.inparams = append(result.inparams,
-			s.assignParamOrReturn(rfsl[0], false))
+			s.assignParamOrReturn(r.Type, r.Nname, false))
 	}
 
 	// Inputs
 	ifsl := ft.Params.FieldSlice()
 	for _, f := range ifsl {
 		result.inparams = append(result.inparams,
-			s.assignParamOrReturn(f, false))
+			s.assignParamOrReturn(f.Type, f.Nname, false))
 	}
 	s.stackOffset = types.Rnd(s.stackOffset, int64(types.RegSize))
+	result.inRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
 
 	// Outputs
 	s.rUsed = RegAmounts{}
 	ofsl := ft.Results.FieldSlice()
 	for _, f := range ofsl {
-		result.outparams = append(result.outparams, s.assignParamOrReturn(f, true))
+		result.outparams = append(result.outparams, s.assignParamOrReturn(f.Type, f.Nname, true))
 	}
 	// The spill area is at a register-aligned offset and its size is rounded up to a register alignment.
 	// TODO in theory could align offset only to minimum required by spilled data types.
 	result.offsetToSpillArea = alignTo(s.stackOffset, types.RegSize)
 	result.spillAreaSize = alignTo(s.spillOffset, types.RegSize)
+	result.outRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
 
 	return result
 }
@@ -460,17 +523,15 @@ func (state *assignState) regassign(pt *types.Type) bool {
 // of field f to determine whether it can be register assigned.
 // The result of the analysis is recorded in the result
 // ABIParamResultInfo held in 'state'.
-func (state *assignState) assignParamOrReturn(f *types.Field, isReturn bool) ABIParamAssignment {
-	// TODO(register args) ? seems like "struct" and "fields" is not right anymore for describing function parameters
-	pt := f.Type
+func (state *assignState) assignParamOrReturn(pt *types.Type, n types.Object, isReturn bool) ABIParamAssignment {
 	state.pUsed = RegAmounts{}
 	if pt.Width == types.BADWIDTH {
 		panic("should never happen")
 	} else if pt.Width == 0 {
-		return state.stackAllocate(pt, f.Nname)
+		return state.stackAllocate(pt, n)
 	} else if state.regassign(pt) {
-		return state.regAllocate(pt, f.Nname, isReturn)
+		return state.regAllocate(pt, n, isReturn)
 	} else {
-		return state.stackAllocate(pt, f.Nname)
+		return state.stackAllocate(pt, n)
 	}
 }
diff --git a/src/cmd/compile/internal/ssa/cse.go b/src/cmd/compile/internal/ssa/cse.go
index f78527410c..ade5e0648e 100644
--- a/src/cmd/compile/internal/ssa/cse.go
+++ b/src/cmd/compile/internal/ssa/cse.go
@@ -299,7 +299,7 @@ func cmpVal(v, w *Value, auxIDs auxmap) types.Cmp {
 	// OpSelect is a pseudo-op. We need to be more aggressive
 	// regarding CSE to keep multiple OpSelect's of the same
 	// argument from existing.
-	if v.Op != OpSelect0 && v.Op != OpSelect1 {
+	if v.Op != OpSelect0 && v.Op != OpSelect1 && v.Op != OpSelectN {
 		if tc := v.Type.Compare(w.Type); tc != types.CMPeq {
 			return tc
 		}
diff --git a/src/cmd/compile/internal/ssa/expand_calls.go b/src/cmd/compile/internal/ssa/expand_calls.go
index 85d6fda427..292b0b41ce 100644
--- a/src/cmd/compile/internal/ssa/expand_calls.go
+++ b/src/cmd/compile/internal/ssa/expand_calls.go
@@ -170,6 +170,7 @@ type expandState struct {
 	sdom         SparseTree
 	common       map[selKey]*Value
 	offsets      map[offsetKey]*Value
+	memForCall   map[ID]*Value // For a call, need to know the unique selector that gets the mem.
 }
 
 // intPairTypes returns the pair of 32-bit int types needed to encode a 64-bit integer type on a target
@@ -280,7 +281,6 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 		if !x.isAlreadyExpandedAggregateType(selector.Type) {
 			if leafType == selector.Type { // OpIData leads us here, sometimes.
 				leaf.copyOf(selector)
-
 			} else {
 				x.f.Fatalf("Unexpected OpArg type, selector=%s, leaf=%s\n", selector.LongString(), leaf.LongString())
 			}
@@ -357,13 +357,43 @@ 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.
-			leaf.copyOf(call)
+			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(fmt.Errorf("aux.abiInfo nil for call %s", call.LongString()))
+				}
+				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)
+			}
 		} else {
 			leafType := removeTrivialWrapperTypes(leaf.Type)
 			if x.canSSAType(leafType) {
 				pt := types.NewPtr(leafType)
 				off := x.offsetFrom(x.sp, offset+aux.OffsetOfResult(which), pt)
 				// 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
+					}
+				}
 				if leaf.Block == call.Block {
 					leaf.reset(OpLoad)
 					leaf.SetArgs2(off, call)
@@ -835,6 +865,7 @@ func expandCalls(f *Func) {
 		sdom:         f.Sdom(),
 		common:       make(map[selKey]*Value),
 		offsets:      make(map[offsetKey]*Value),
+		memForCall:   make(map[ID]*Value),
 	}
 
 	// For 32-bit, need to deal with decomposition of 64-bit integers, which depends on endianness.
@@ -1173,7 +1204,8 @@ func expandCalls(f *Func) {
 			switch v.Op {
 			case OpStaticLECall:
 				v.Op = OpStaticCall
-				v.Type = types.TypeMem
+				// TODO need to insert all the register types.
+				v.Type = types.NewResults([]*types.Type{types.TypeMem})
 			case OpClosureLECall:
 				v.Op = OpClosureCall
 				v.Type = types.TypeMem
diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 1784923224..fab45243ed 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -1970,37 +1970,6 @@
 
 (Sqrt (Const64F [c])) && !math.IsNaN(math.Sqrt(c)) => (Const64F [math.Sqrt(c)])
 
-// recognize runtime.newobject and don't Zero/Nilcheck it
-(Zero (Load (OffPtr [c] (SP)) mem) mem)
-	&& mem.Op == OpStaticCall
-	&& isSameCall(mem.Aux, "runtime.newobject")
-	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	=> mem
-(Store (Load (OffPtr [c] (SP)) mem) x mem)
-	&& isConstZero(x)
-	&& mem.Op == OpStaticCall
-	&& isSameCall(mem.Aux, "runtime.newobject")
-	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	=> mem
-(Store (OffPtr (Load (OffPtr [c] (SP)) mem)) x mem)
-	&& isConstZero(x)
-	&& mem.Op == OpStaticCall
-	&& isSameCall(mem.Aux, "runtime.newobject")
-	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	=> mem
-// nil checks just need to rewrite to something useless.
-// they will be deadcode eliminated soon afterwards.
-(NilCheck (Load (OffPtr [c] (SP)) (StaticCall {sym} _)) _)
-	&& isSameCall(sym, "runtime.newobject")
-	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
-	=> (Invalid)
-(NilCheck (OffPtr (Load (OffPtr [c] (SP)) (StaticCall {sym} _))) _)
-	&& isSameCall(sym, "runtime.newobject")
-	&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
-	=> (Invalid)
-
 // for rewriting results of some late-expanded rewrites (below)
 (SelectN [0] (MakeResult a ___)) => a
 (SelectN [1] (MakeResult a b ___)) => b
@@ -2021,12 +1990,12 @@
 	&& isSameCall(call.Aux, "runtime.newobject")
 	=> mem
 
-(NilCheck (SelectN [0] call:(StaticLECall _ _)) (SelectN [1] call))
+(NilCheck (SelectN [0] call:(StaticLECall _ _)) _)
 	&& isSameCall(call.Aux, "runtime.newobject")
 	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
 	=> (Invalid)
 
-(NilCheck (OffPtr (SelectN [0] call:(StaticLECall _ _))) (SelectN [1] call))
+(NilCheck (OffPtr (SelectN [0] call:(StaticLECall _ _))) _)
 	&& isSameCall(call.Aux, "runtime.newobject")
 	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
 	=> (Invalid)
@@ -2083,15 +2052,19 @@
 (IsNonNil (Addr _)) => (ConstBool [true])
 (IsNonNil (LocalAddr _ _)) => (ConstBool [true])
 
+// TODO REGISTER ARGS this will need revision.
+// Because expand calls runs after prove, constants useful to this pattern may not appear
+// In the future both versions need to exist; the memory and register variants.
+
 // Inline small or disjoint runtime.memmove calls with constant length.
 // See the comment in op Move in genericOps.go for discussion of the type.
-(StaticCall {sym} s1:(Store _ (Const(64|32) [sz]) s2:(Store  _ src s3:(Store {t} _ dst mem))))
+(SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const(64|32) [sz]) s2:(Store  _ src s3:(Store {t} _ dst mem)))))
 	&& sz >= 0
 	&& isSameCall(sym, "runtime.memmove")
 	&& t.IsPtr() // avoids TUINTPTR, see issue 30061
 	&& s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1
 	&& isInlinableMemmove(dst, src, int64(sz), config)
-	&& clobber(s1, s2, s3)
+	&& clobber(s1, s2, s3, call)
 	=> (Move {t.Elem()} [int64(sz)] dst src mem)
 
 // Inline small or disjoint runtime.memmove calls with constant length.
@@ -2105,13 +2078,6 @@
 	&& clobber(call)
 	=> (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
 
-// De-virtualize interface calls into static calls.
-// Note that (ITab (IMake)) doesn't get
-// rewritten until after the first opt pass,
-// so this rule should trigger reliably.
-(InterCall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) mem) && devirt(v, auxCall, itab, off) != nil =>
-	(StaticCall [int32(argsize)] {devirt(v, auxCall, itab, off)} mem)
-
 // De-virtualize late-expanded interface calls into late-expanded static calls.
 // Note that (ITab (IMake)) doesn't get rewritten until after the first opt pass,
 // so this rule should trigger reliably.
@@ -2499,8 +2465,8 @@
 				(Store {t5} (OffPtr <tt5> [o5] dst) d4
 					(Zero {t1} [n] dst mem)))))
 
-// TODO this does not fire before call expansion; is that acceptable?
-(StaticCall {sym} x) && needRaceCleanup(sym, v) => x
+(SelectN [0] call:(StaticLECall {sym} a x)) && needRaceCleanup(sym, call) && clobber(call) => x
+(SelectN [0] call:(StaticLECall {sym} x)) && needRaceCleanup(sym, call) && clobber(call) => x
 
 // Collapse moving A -> B -> C into just A -> C.
 // Later passes (deadstore, elim unread auto) will remove the A -> B move, if possible.
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index 23a2d74b14..043f445c16 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -396,7 +396,7 @@ var genericOps = []opData{
 	// 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=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.
 	{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.
diff --git a/src/cmd/compile/internal/ssa/location.go b/src/cmd/compile/internal/ssa/location.go
index 4cd0ac8d77..af0a913d17 100644
--- a/src/cmd/compile/internal/ssa/location.go
+++ b/src/cmd/compile/internal/ssa/location.go
@@ -88,6 +88,20 @@ func (t LocPair) String() string {
 	return fmt.Sprintf("<%s,%s>", n0, n1)
 }
 
+type LocResults []Location
+
+func (t LocResults) String() string {
+	s := "<"
+	a := ""
+	for _, r := range t {
+		a += s
+		s = ","
+		a += r.String()
+	}
+	a += ">"
+	return a
+}
+
 type ArgPair struct {
 	reg *Register
 	mem LocalSlot
diff --git a/src/cmd/compile/internal/ssa/lower.go b/src/cmd/compile/internal/ssa/lower.go
index f332b2e028..f6b2bf86a9 100644
--- a/src/cmd/compile/internal/ssa/lower.go
+++ b/src/cmd/compile/internal/ssa/lower.go
@@ -21,7 +21,7 @@ func checkLower(f *Func) {
 				continue // lowered
 			}
 			switch v.Op {
-			case OpSP, OpSB, OpInitMem, OpArg, OpPhi, OpVarDef, OpVarKill, OpVarLive, OpKeepAlive, OpSelect0, OpSelect1, OpConvert, OpInlMark:
+			case OpSP, OpSB, OpInitMem, OpArg, OpPhi, OpVarDef, OpVarKill, OpVarLive, OpKeepAlive, OpSelect0, OpSelect1, OpSelectN, OpConvert, OpInlMark:
 				continue // ok not to lower
 			case OpGetG:
 				if f.Config.hasGReg {
diff --git a/src/cmd/compile/internal/ssa/op.go b/src/cmd/compile/internal/ssa/op.go
index 55e0602f2f..6949bdca31 100644
--- a/src/cmd/compile/internal/ssa/op.go
+++ b/src/cmd/compile/internal/ssa/op.go
@@ -203,9 +203,19 @@ func (a *AuxCall) String() string {
 	return fn + "}"
 }
 
+func ACParamsToTypes(ps []Param) (ts []*types.Type) {
+	for _, p := range ps {
+		ts = append(ts, p.Type)
+	}
+	return
+}
+
 // StaticAuxCall returns an AuxCall for a static call.
 func StaticAuxCall(sym *obj.LSym, args []Param, results []Param, paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
 	// TODO Create regInfo for AuxCall
+	if paramResultInfo == nil {
+		panic(fmt.Errorf("Nil paramResultInfo, sym=%v", sym))
+	}
 	return &AuxCall{Fn: sym, args: args, results: results, abiInfo: paramResultInfo}
 }
 
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 10ea57b36b..2d37ae4357 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -35435,7 +35435,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:    "StaticCall",
 		auxType: auxCallOff,
-		argLen:  1,
+		argLen:  -1,
 		call:    true,
 		generic: true,
 	},
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index 8c25b1c81d..99e101281b 100644
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -761,6 +761,9 @@ func (s *regAllocState) advanceUses(v *Value) {
 // current instruction.
 func (s *regAllocState) liveAfterCurrentInstruction(v *Value) bool {
 	u := s.values[v.ID].uses
+	if u == nil {
+		panic(fmt.Errorf("u is nil, v = %s, s.values[v.ID] = %v", v.LongString(), s.values[v.ID]))
+	}
 	d := u.dist
 	for u != nil && u.dist == d {
 		u = u.next
@@ -1208,13 +1211,17 @@ func (s *regAllocState) regalloc(f *Func) {
 				s.sb = v.ID
 				continue
 			}
-			if v.Op == OpSelect0 || v.Op == OpSelect1 {
+			if v.Op == OpSelect0 || v.Op == OpSelect1 || v.Op == OpSelectN {
 				if s.values[v.ID].needReg {
-					var i = 0
-					if v.Op == OpSelect1 {
-						i = 1
+					if v.Op == OpSelectN {
+						s.assignReg(register(s.f.getHome(v.Args[0].ID).(LocResults)[int(v.AuxInt)].(*Register).num), v, v)
+					} else {
+						var i = 0
+						if v.Op == OpSelect1 {
+							i = 1
+						}
+						s.assignReg(register(s.f.getHome(v.Args[0].ID).(LocPair)[i].(*Register).num), v, v)
 					}
-					s.assignReg(register(s.f.getHome(v.Args[0].ID).(LocPair)[i].(*Register).num), v, v)
 				}
 				b.Values = append(b.Values, v)
 				s.advanceUses(v)
@@ -1767,6 +1774,9 @@ func (s *regAllocState) placeSpills() {
 		// put the spill of v.  At the start "best" is the best place
 		// we have found so far.
 		// TODO: find a way to make this O(1) without arbitrary cutoffs.
+		if v == nil {
+			panic(fmt.Errorf("nil v, s.orig[%d], vi = %v, spill = %s", i, vi, spill.LongString()))
+		}
 		best := v.Block
 		bestArg := v
 		var bestDepth int16
diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index ac6278ab9d..19b97a3ed1 100644
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -793,7 +793,10 @@ func devirtLESym(v *Value, aux Aux, sym Sym, offset int64) *obj.LSym {
 
 func devirtLECall(v *Value, sym *obj.LSym) *Value {
 	v.Op = OpStaticLECall
-	v.Aux.(*AuxCall).Fn = sym
+	auxcall := v.Aux.(*AuxCall)
+	auxcall.Fn = sym
+	// TODO(register args) this should not be necessary when fully transition to the new register ABI.
+	auxcall.abiInfo = v.Block.Func.ABIDefault.ABIAnalyzeTypes(nil, ACParamsToTypes(auxcall.args), ACParamsToTypes(auxcall.results))
 	v.RemoveArg(0)
 	return v
 }
@@ -1617,7 +1620,7 @@ func needRaceCleanup(sym *AuxCall, v *Value) bool {
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			switch v.Op {
-			case OpStaticCall:
+			case OpStaticCall, OpStaticLECall:
 				// Check for racefuncenter/racefuncenterfp will encounter racefuncexit and vice versa.
 				// Allow calls to panic*
 				s := v.Aux.(*AuxCall).Fn.String()
@@ -1632,15 +1635,20 @@ func needRaceCleanup(sym *AuxCall, v *Value) bool {
 				return false
 			case OpPanicBounds, OpPanicExtend:
 				// Note: these are panic generators that are ok (like the static calls above).
-			case OpClosureCall, OpInterCall:
+			case OpClosureCall, OpInterCall, OpClosureLECall, OpInterLECall:
 				// We must keep the race functions if there are any other call types.
 				return false
 			}
 		}
 	}
 	if isSameCall(sym, "runtime.racefuncenter") {
+		// TODO REGISTER ABI this needs to be cleaned up.
 		// If we're removing racefuncenter, remove its argument as well.
 		if v.Args[0].Op != OpStore {
+			if v.Op == OpStaticLECall {
+				// there is no store, yet.
+				return true
+			}
 			return false
 		}
 		mem := v.Args[0].Args[2]
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index 958e24d29f..e5a27199a7 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -122,8 +122,6 @@ func rewriteValuegeneric(v *Value) bool {
 		return rewriteValuegeneric_OpEqSlice(v)
 	case OpIMake:
 		return rewriteValuegeneric_OpIMake(v)
-	case OpInterCall:
-		return rewriteValuegeneric_OpInterCall(v)
 	case OpInterLECall:
 		return rewriteValuegeneric_OpInterLECall(v)
 	case OpIsInBounds:
@@ -392,8 +390,6 @@ func rewriteValuegeneric(v *Value) bool {
 		return rewriteValuegeneric_OpSlicemask(v)
 	case OpSqrt:
 		return rewriteValuegeneric_OpSqrt(v)
-	case OpStaticCall:
-		return rewriteValuegeneric_OpStaticCall(v)
 	case OpStaticLECall:
 		return rewriteValuegeneric_OpStaticLECall(v)
 	case OpStore:
@@ -8542,52 +8538,6 @@ func rewriteValuegeneric_OpIMake(v *Value) bool {
 	}
 	return false
 }
-func rewriteValuegeneric_OpInterCall(v *Value) bool {
-	v_1 := v.Args[1]
-	v_0 := v.Args[0]
-	// match: (InterCall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) mem)
-	// cond: devirt(v, auxCall, itab, off) != nil
-	// result: (StaticCall [int32(argsize)] {devirt(v, auxCall, itab, off)} mem)
-	for {
-		argsize := auxIntToInt32(v.AuxInt)
-		auxCall := auxToCall(v.Aux)
-		if v_0.Op != OpLoad {
-			break
-		}
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpOffPtr {
-			break
-		}
-		off := auxIntToInt64(v_0_0.AuxInt)
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpITab {
-			break
-		}
-		v_0_0_0_0 := v_0_0_0.Args[0]
-		if v_0_0_0_0.Op != OpIMake {
-			break
-		}
-		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
-		if v_0_0_0_0_0.Op != OpAddr {
-			break
-		}
-		itab := auxToSym(v_0_0_0_0_0.Aux)
-		v_0_0_0_0_0_0 := v_0_0_0_0_0.Args[0]
-		if v_0_0_0_0_0_0.Op != OpSB {
-			break
-		}
-		mem := v_1
-		if !(devirt(v, auxCall, itab, off) != nil) {
-			break
-		}
-		v.reset(OpStaticCall)
-		v.AuxInt = int32ToAuxInt(int32(argsize))
-		v.Aux = callToAux(devirt(v, auxCall, itab, off))
-		v.AddArg(mem)
-		return true
-	}
-	return false
-}
 func rewriteValuegeneric_OpInterLECall(v *Value) bool {
 	// match: (InterLECall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) ___)
 	// cond: devirtLESym(v, auxCall, itab, off) != nil
@@ -16113,7 +16063,6 @@ func rewriteValuegeneric_OpNilCheck(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
 	b := v.Block
-	config := b.Func.Config
 	fe := b.Func.fe
 	// match: (NilCheck (GetG mem) mem)
 	// result: mem
@@ -16128,67 +16077,7 @@ func rewriteValuegeneric_OpNilCheck(v *Value) bool {
 		v.copyOf(mem)
 		return true
 	}
-	// match: (NilCheck (Load (OffPtr [c] (SP)) (StaticCall {sym} _)) _)
-	// cond: isSameCall(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")
-	// result: (Invalid)
-	for {
-		if v_0.Op != OpLoad {
-			break
-		}
-		_ = v_0.Args[1]
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpOffPtr {
-			break
-		}
-		c := auxIntToInt64(v_0_0.AuxInt)
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpSP {
-			break
-		}
-		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpStaticCall {
-			break
-		}
-		sym := auxToCall(v_0_1.Aux)
-		if !(isSameCall(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
-			break
-		}
-		v.reset(OpInvalid)
-		return true
-	}
-	// match: (NilCheck (OffPtr (Load (OffPtr [c] (SP)) (StaticCall {sym} _))) _)
-	// cond: isSameCall(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")
-	// result: (Invalid)
-	for {
-		if v_0.Op != OpOffPtr {
-			break
-		}
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpLoad {
-			break
-		}
-		_ = v_0_0.Args[1]
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpOffPtr {
-			break
-		}
-		c := auxIntToInt64(v_0_0_0.AuxInt)
-		v_0_0_0_0 := v_0_0_0.Args[0]
-		if v_0_0_0_0.Op != OpSP {
-			break
-		}
-		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpStaticCall {
-			break
-		}
-		sym := auxToCall(v_0_0_1.Aux)
-		if !(isSameCall(sym, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
-			break
-		}
-		v.reset(OpInvalid)
-		return true
-	}
-	// match: (NilCheck (SelectN [0] call:(StaticLECall _ _)) (SelectN [1] call))
+	// match: (NilCheck (SelectN [0] call:(StaticLECall _ _)) _)
 	// cond: isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")
 	// result: (Invalid)
 	for {
@@ -16196,13 +16085,13 @@ func rewriteValuegeneric_OpNilCheck(v *Value) bool {
 			break
 		}
 		call := v_0.Args[0]
-		if call.Op != OpStaticLECall || len(call.Args) != 2 || v_1.Op != OpSelectN || auxIntToInt64(v_1.AuxInt) != 1 || call != v_1.Args[0] || !(isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
+		if call.Op != OpStaticLECall || len(call.Args) != 2 || !(isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
 			break
 		}
 		v.reset(OpInvalid)
 		return true
 	}
-	// match: (NilCheck (OffPtr (SelectN [0] call:(StaticLECall _ _))) (SelectN [1] call))
+	// match: (NilCheck (OffPtr (SelectN [0] call:(StaticLECall _ _))) _)
 	// cond: isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")
 	// result: (Invalid)
 	for {
@@ -16214,7 +16103,7 @@ func rewriteValuegeneric_OpNilCheck(v *Value) bool {
 			break
 		}
 		call := v_0_0.Args[0]
-		if call.Op != OpStaticLECall || len(call.Args) != 2 || v_1.Op != OpSelectN || auxIntToInt64(v_1.AuxInt) != 1 || call != v_1.Args[0] || !(isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
+		if call.Op != OpStaticLECall || len(call.Args) != 2 || !(isSameCall(call.Aux, "runtime.newobject") && warnRule(fe.Debug_checknil(), v, "removed nil check")) {
 			break
 		}
 		v.reset(OpInvalid)
@@ -20799,6 +20688,94 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
 		v.copyOf(c)
 		return true
 	}
+	// match: (SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const64 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem)))))
+	// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
+	// result: (Move {t.Elem()} [int64(sz)] dst src mem)
+	for {
+		if auxIntToInt64(v.AuxInt) != 0 {
+			break
+		}
+		call := v_0
+		if call.Op != OpStaticCall || len(call.Args) != 1 {
+			break
+		}
+		sym := auxToCall(call.Aux)
+		s1 := call.Args[0]
+		if s1.Op != OpStore {
+			break
+		}
+		_ = s1.Args[2]
+		s1_1 := s1.Args[1]
+		if s1_1.Op != OpConst64 {
+			break
+		}
+		sz := auxIntToInt64(s1_1.AuxInt)
+		s2 := s1.Args[2]
+		if s2.Op != OpStore {
+			break
+		}
+		_ = s2.Args[2]
+		src := s2.Args[1]
+		s3 := s2.Args[2]
+		if s3.Op != OpStore {
+			break
+		}
+		t := auxToType(s3.Aux)
+		mem := s3.Args[2]
+		dst := s3.Args[1]
+		if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
+			break
+		}
+		v.reset(OpMove)
+		v.AuxInt = int64ToAuxInt(int64(sz))
+		v.Aux = typeToAux(t.Elem())
+		v.AddArg3(dst, src, mem)
+		return true
+	}
+	// match: (SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const32 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem)))))
+	// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
+	// result: (Move {t.Elem()} [int64(sz)] dst src mem)
+	for {
+		if auxIntToInt64(v.AuxInt) != 0 {
+			break
+		}
+		call := v_0
+		if call.Op != OpStaticCall || len(call.Args) != 1 {
+			break
+		}
+		sym := auxToCall(call.Aux)
+		s1 := call.Args[0]
+		if s1.Op != OpStore {
+			break
+		}
+		_ = s1.Args[2]
+		s1_1 := s1.Args[1]
+		if s1_1.Op != OpConst32 {
+			break
+		}
+		sz := auxIntToInt32(s1_1.AuxInt)
+		s2 := s1.Args[2]
+		if s2.Op != OpStore {
+			break
+		}
+		_ = s2.Args[2]
+		src := s2.Args[1]
+		s3 := s2.Args[2]
+		if s3.Op != OpStore {
+			break
+		}
+		t := auxToType(s3.Aux)
+		mem := s3.Args[2]
+		dst := s3.Args[1]
+		if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
+			break
+		}
+		v.reset(OpMove)
+		v.AuxInt = int64ToAuxInt(int64(sz))
+		v.Aux = typeToAux(t.Elem())
+		v.AddArg3(dst, src, mem)
+		return true
+	}
 	// match: (SelectN [0] call:(StaticLECall {sym} dst src (Const64 [sz]) mem))
 	// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
 	// result: (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
@@ -20857,6 +20834,44 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
 		v.AddArg3(dst, src, mem)
 		return true
 	}
+	// match: (SelectN [0] call:(StaticLECall {sym} a x))
+	// cond: needRaceCleanup(sym, call) && clobber(call)
+	// result: x
+	for {
+		if auxIntToInt64(v.AuxInt) != 0 {
+			break
+		}
+		call := v_0
+		if call.Op != OpStaticLECall || len(call.Args) != 2 {
+			break
+		}
+		sym := auxToCall(call.Aux)
+		x := call.Args[1]
+		if !(needRaceCleanup(sym, call) && clobber(call)) {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
+	// match: (SelectN [0] call:(StaticLECall {sym} x))
+	// cond: needRaceCleanup(sym, call) && clobber(call)
+	// result: x
+	for {
+		if auxIntToInt64(v.AuxInt) != 0 {
+			break
+		}
+		call := v_0
+		if call.Op != OpStaticLECall || len(call.Args) != 1 {
+			break
+		}
+		sym := auxToCall(call.Aux)
+		x := call.Args[0]
+		if !(needRaceCleanup(sym, call) && clobber(call)) {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpSignExt16to32(v *Value) bool {
@@ -21307,98 +21322,6 @@ func rewriteValuegeneric_OpSqrt(v *Value) bool {
 	}
 	return false
 }
-func rewriteValuegeneric_OpStaticCall(v *Value) bool {
-	v_0 := v.Args[0]
-	b := v.Block
-	config := b.Func.Config
-	// match: (StaticCall {sym} s1:(Store _ (Const64 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem))))
-	// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3)
-	// result: (Move {t.Elem()} [int64(sz)] dst src mem)
-	for {
-		sym := auxToCall(v.Aux)
-		s1 := v_0
-		if s1.Op != OpStore {
-			break
-		}
-		_ = s1.Args[2]
-		s1_1 := s1.Args[1]
-		if s1_1.Op != OpConst64 {
-			break
-		}
-		sz := auxIntToInt64(s1_1.AuxInt)
-		s2 := s1.Args[2]
-		if s2.Op != OpStore {
-			break
-		}
-		_ = s2.Args[2]
-		src := s2.Args[1]
-		s3 := s2.Args[2]
-		if s3.Op != OpStore {
-			break
-		}
-		t := auxToType(s3.Aux)
-		mem := s3.Args[2]
-		dst := s3.Args[1]
-		if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3)) {
-			break
-		}
-		v.reset(OpMove)
-		v.AuxInt = int64ToAuxInt(int64(sz))
-		v.Aux = typeToAux(t.Elem())
-		v.AddArg3(dst, src, mem)
-		return true
-	}
-	// match: (StaticCall {sym} s1:(Store _ (Const32 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem))))
-	// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3)
-	// result: (Move {t.Elem()} [int64(sz)] dst src mem)
-	for {
-		sym := auxToCall(v.Aux)
-		s1 := v_0
-		if s1.Op != OpStore {
-			break
-		}
-		_ = s1.Args[2]
-		s1_1 := s1.Args[1]
-		if s1_1.Op != OpConst32 {
-			break
-		}
-		sz := auxIntToInt32(s1_1.AuxInt)
-		s2 := s1.Args[2]
-		if s2.Op != OpStore {
-			break
-		}
-		_ = s2.Args[2]
-		src := s2.Args[1]
-		s3 := s2.Args[2]
-		if s3.Op != OpStore {
-			break
-		}
-		t := auxToType(s3.Aux)
-		mem := s3.Args[2]
-		dst := s3.Args[1]
-		if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3)) {
-			break
-		}
-		v.reset(OpMove)
-		v.AuxInt = int64ToAuxInt(int64(sz))
-		v.Aux = typeToAux(t.Elem())
-		v.AddArg3(dst, src, mem)
-		return true
-	}
-	// match: (StaticCall {sym} x)
-	// cond: needRaceCleanup(sym, v)
-	// result: x
-	for {
-		sym := auxToCall(v.Aux)
-		x := v_0
-		if !(needRaceCleanup(sym, v)) {
-			break
-		}
-		v.copyOf(x)
-		return true
-	}
-	return false
-}
 func rewriteValuegeneric_OpStaticLECall(v *Value) bool {
 	b := v.Block
 	typ := &b.Func.Config.Types
@@ -21442,7 +21365,6 @@ func rewriteValuegeneric_OpStore(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
 	b := v.Block
-	config := b.Func.Config
 	fe := b.Func.fe
 	// match: (Store {t1} p1 (Load <t2> p2 mem) mem)
 	// cond: isSamePtr(p1, p2) && t2.Size() == t1.Size()
@@ -21890,58 +21812,6 @@ func rewriteValuegeneric_OpStore(v *Value) bool {
 		v.AddArg3(dst, e, mem)
 		return true
 	}
-	// match: (Store (Load (OffPtr [c] (SP)) mem) x mem)
-	// cond: isConstZero(x) && mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize
-	// result: mem
-	for {
-		if v_0.Op != OpLoad {
-			break
-		}
-		mem := v_0.Args[1]
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpOffPtr {
-			break
-		}
-		c := auxIntToInt64(v_0_0.AuxInt)
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpSP {
-			break
-		}
-		x := v_1
-		if mem != v_2 || !(isConstZero(x) && mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize) {
-			break
-		}
-		v.copyOf(mem)
-		return true
-	}
-	// match: (Store (OffPtr (Load (OffPtr [c] (SP)) mem)) x mem)
-	// cond: isConstZero(x) && mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize
-	// result: mem
-	for {
-		if v_0.Op != OpOffPtr {
-			break
-		}
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpLoad {
-			break
-		}
-		mem := v_0_0.Args[1]
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpOffPtr {
-			break
-		}
-		c := auxIntToInt64(v_0_0_0.AuxInt)
-		v_0_0_0_0 := v_0_0_0.Args[0]
-		if v_0_0_0_0.Op != OpSP {
-			break
-		}
-		x := v_1
-		if mem != v_2 || !(isConstZero(x) && mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize) {
-			break
-		}
-		v.copyOf(mem)
-		return true
-	}
 	// match: (Store (SelectN [0] call:(StaticLECall _ _)) x mem:(SelectN [1] call))
 	// cond: isConstZero(x) && isSameCall(call.Aux, "runtime.newobject")
 	// result: mem
@@ -24660,27 +24530,6 @@ func rewriteValuegeneric_OpZero(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
 	b := v.Block
-	config := b.Func.Config
-	// match: (Zero (Load (OffPtr [c] (SP)) mem) mem)
-	// cond: mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize
-	// result: mem
-	for {
-		if v_0.Op != OpLoad {
-			break
-		}
-		mem := v_0.Args[1]
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpOffPtr {
-			break
-		}
-		c := auxIntToInt64(v_0_0.AuxInt)
-		v_0_0_0 := v_0_0.Args[0]
-		if v_0_0_0.Op != OpSP || mem != v_1 || !(mem.Op == OpStaticCall && isSameCall(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize) {
-			break
-		}
-		v.copyOf(mem)
-		return true
-	}
 	// match: (Zero (SelectN [0] call:(StaticLECall _ _)) mem:(SelectN [1] call))
 	// cond: isSameCall(call.Aux, "runtime.newobject")
 	// result: mem
diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go
index 8facb91100..6b34310db7 100644
--- a/src/cmd/compile/internal/ssa/schedule.go
+++ b/src/cmd/compile/internal/ssa/schedule.go
@@ -145,7 +145,7 @@ func schedule(f *Func) {
 				// reduce register pressure. It also helps make sure
 				// VARDEF ops are scheduled before the corresponding LEA.
 				score[v.ID] = ScoreMemory
-			case v.Op == OpSelect0 || v.Op == OpSelect1:
+			case v.Op == OpSelect0 || v.Op == OpSelect1 || v.Op == OpSelectN:
 				// Schedule the pseudo-op of reading part of a tuple
 				// immediately after the tuple-generating op, since
 				// this value is already live. This also removes its
@@ -270,6 +270,20 @@ func schedule(f *Func) {
 					tuples[v.Args[0].ID] = make([]*Value, 2)
 				}
 				tuples[v.Args[0].ID][1] = v
+			case v.Op == OpSelectN:
+				if tuples[v.Args[0].ID] == nil {
+					tuples[v.Args[0].ID] = make([]*Value, v.Args[0].Type.NumFields())
+				}
+				tuples[v.Args[0].ID][v.AuxInt] = v
+			case v.Type.IsResults() && tuples[v.ID] != nil:
+				tup := tuples[v.ID]
+				for i := len(tup) - 1; i >= 0; i-- {
+					if tup[i] != nil {
+						order = append(order, tup[i])
+					}
+				}
+				delete(tuples, v.ID)
+				order = append(order, v)
 			case v.Type.IsTuple() && tuples[v.ID] != nil:
 				if tuples[v.ID][1] != nil {
 					order = append(order, tuples[v.ID][1])
diff --git a/src/cmd/compile/internal/ssa/tighten.go b/src/cmd/compile/internal/ssa/tighten.go
index 5dfc453649..bd08334a5f 100644
--- a/src/cmd/compile/internal/ssa/tighten.go
+++ b/src/cmd/compile/internal/ssa/tighten.go
@@ -18,10 +18,11 @@ func tighten(f *Func) {
 				continue
 			}
 			switch v.Op {
-			case OpPhi, OpArg, OpSelect0, OpSelect1:
+			case OpPhi, OpArg, OpSelect0, OpSelect1, OpSelectN:
 				// Phis need to stay in their block.
 				// Arg must stay in the entry block.
 				// Tuple selectors must stay with the tuple generator.
+				// SelectN is typically, ultimately, a register.
 				continue
 			}
 			if v.MemoryArg() != nil {
diff --git a/src/cmd/compile/internal/ssa/tuple.go b/src/cmd/compile/internal/ssa/tuple.go
index 38deabf83d..289df40431 100644
--- a/src/cmd/compile/internal/ssa/tuple.go
+++ b/src/cmd/compile/internal/ssa/tuple.go
@@ -4,8 +4,8 @@
 
 package ssa
 
-// tightenTupleSelectors ensures that tuple selectors (Select0 and
-// Select1 ops) are in the same block as their tuple generator. The
+// tightenTupleSelectors ensures that tuple selectors (Select0, Select1,
+// and SelectN ops) are in the same block as their tuple generator. The
 // function also ensures that there are no duplicate tuple selectors.
 // These properties are expected by the scheduler but may not have
 // been maintained by the optimization pipeline up to this point.
@@ -13,28 +13,40 @@ package ssa
 // See issues 16741 and 39472.
 func tightenTupleSelectors(f *Func) {
 	selectors := make(map[struct {
-		id ID
-		op Op
+		id    ID
+		which int
 	}]*Value)
 	for _, b := range f.Blocks {
 		for _, selector := range b.Values {
-			if selector.Op != OpSelect0 && selector.Op != OpSelect1 {
+			// Key fields for de-duplication
+			var tuple *Value
+			idx := 0
+			switch selector.Op {
+			default:
 				continue
-			}
-
-			// Get the tuple generator to use as a key for de-duplication.
-			tuple := selector.Args[0]
-			if !tuple.Type.IsTuple() {
-				f.Fatalf("arg of tuple selector %s is not a tuple: %s", selector.String(), tuple.LongString())
+			case OpSelect1:
+				idx = 1
+				fallthrough
+			case OpSelect0:
+				tuple = selector.Args[0]
+				if !tuple.Type.IsTuple() {
+					f.Fatalf("arg of tuple selector %s is not a tuple: %s", selector.String(), tuple.LongString())
+				}
+			case OpSelectN:
+				tuple = selector.Args[0]
+				idx = int(selector.AuxInt)
+				if !tuple.Type.IsResults() {
+					f.Fatalf("arg of result selector %s is not a results: %s", selector.String(), tuple.LongString())
+				}
 			}
 
 			// If there is a pre-existing selector in the target block then
 			// use that. Do this even if the selector is already in the
 			// target block to avoid duplicate tuple selectors.
 			key := struct {
-				id ID
-				op Op
-			}{tuple.ID, selector.Op}
+				id    ID
+				which int
+			}{tuple.ID, idx}
 			if t := selectors[key]; t != nil {
 				if selector != t {
 					selector.copyOf(t)
diff --git a/src/cmd/compile/internal/ssa/writebarrier.go b/src/cmd/compile/internal/ssa/writebarrier.go
index 7d375da128..0af039577f 100644
--- a/src/cmd/compile/internal/ssa/writebarrier.go
+++ b/src/cmd/compile/internal/ssa/writebarrier.go
@@ -487,12 +487,14 @@ func wbcall(pos src.XPos, b *Block, fn, typ *obj.LSym, ptr, val, mem, sp, sb *Va
 	off := config.ctxt.FixedFrameSize()
 
 	var ACArgs []Param
+	var argTypes []*types.Type
 	if typ != nil { // for typedmemmove
 		taddr := b.NewValue1A(pos, OpAddr, b.Func.Config.Types.Uintptr, typ, sb)
 		off = round(off, taddr.Type.Alignment())
 		arg := b.NewValue1I(pos, OpOffPtr, taddr.Type.PtrTo(), off, sp)
 		mem = b.NewValue3A(pos, OpStore, types.TypeMem, ptr.Type, arg, taddr, mem)
 		ACArgs = append(ACArgs, Param{Type: b.Func.Config.Types.Uintptr, Offset: int32(off)})
+		argTypes = append(argTypes, b.Func.Config.Types.Uintptr)
 		off += taddr.Type.Size()
 	}
 
@@ -500,6 +502,7 @@ func wbcall(pos src.XPos, b *Block, fn, typ *obj.LSym, ptr, val, mem, sp, sb *Va
 	arg := b.NewValue1I(pos, OpOffPtr, ptr.Type.PtrTo(), off, sp)
 	mem = b.NewValue3A(pos, OpStore, types.TypeMem, ptr.Type, arg, ptr, mem)
 	ACArgs = append(ACArgs, Param{Type: ptr.Type, Offset: int32(off)})
+	argTypes = append(argTypes, ptr.Type)
 	off += ptr.Type.Size()
 
 	if val != nil {
@@ -507,15 +510,15 @@ func wbcall(pos src.XPos, b *Block, fn, typ *obj.LSym, ptr, val, mem, sp, sb *Va
 		arg = b.NewValue1I(pos, OpOffPtr, val.Type.PtrTo(), off, sp)
 		mem = b.NewValue3A(pos, OpStore, types.TypeMem, val.Type, arg, val, mem)
 		ACArgs = append(ACArgs, Param{Type: val.Type, Offset: int32(off)})
+		argTypes = append(argTypes, val.Type)
 		off += val.Type.Size()
 	}
 	off = round(off, config.PtrSize)
 
 	// issue call
-	// TODO(register args) -- will need more details
-	mem = b.NewValue1A(pos, OpStaticCall, types.TypeMem, StaticAuxCall(fn, ACArgs, nil, nil), mem)
+	mem = b.NewValue1A(pos, OpStaticCall, types.TypeResultMem, StaticAuxCall(fn, ACArgs, nil, b.Func.ABIDefault.ABIAnalyzeTypes(nil, argTypes, nil)), mem)
 	mem.AuxInt = off - config.ctxt.FixedFrameSize()
-	return mem
+	return b.NewValue1I(pos, OpSelectN, types.TypeMem, 0, mem)
 }
 
 // round to a multiple of r, r is a power of 2
@@ -563,12 +566,20 @@ func IsReadOnlyGlobalAddr(v *Value) bool {
 
 // IsNewObject reports whether v is a pointer to a freshly allocated & zeroed object at memory state mem.
 func IsNewObject(v *Value, mem *Value) bool {
+	// TODO this will need updating for register args; the OpLoad is wrong.
 	if v.Op != OpLoad {
 		return false
 	}
 	if v.MemoryArg() != mem {
 		return false
 	}
+	if mem.Op != OpSelectN {
+		return false
+	}
+	if mem.Type != types.TypeMem {
+		return false
+	} // assume it is the right selection if true
+	mem = mem.Args[0]
 	if mem.Op != OpStaticCall {
 		return false
 	}
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 20acdbdc66..ba00b9c7f6 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -4734,7 +4734,8 @@ func (s *state) openDeferExit() {
 			aux := ssa.ClosureAuxCall(ACArgs, ACResults)
 			call = s.newValue2A(ssa.OpClosureLECall, aux.LateExpansionResultType(), aux, codeptr, v)
 		} else {
-			aux := ssa.StaticAuxCall(fn.(*ir.Name).Linksym(), ACArgs, ACResults, nil) // TODO will need types for this.
+			aux := ssa.StaticAuxCall(fn.(*ir.Name).Linksym(), ACArgs, ACResults,
+				s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
 			call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 		}
 		callArgs = append(callArgs, s.mem())
@@ -4896,7 +4897,8 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 
 		// Call runtime.deferprocStack with pointer to _defer record.
 		ACArgs = append(ACArgs, ssa.Param{Type: types.Types[types.TUINTPTR], Offset: int32(base.Ctxt.FixedFrameSize())})
-		aux := ssa.StaticAuxCall(ir.Syms.DeferprocStack, ACArgs, ACResults, nil)
+		aux := ssa.StaticAuxCall(ir.Syms.DeferprocStack, ACArgs, ACResults,
+			s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
 		callArgs = append(callArgs, addr, s.mem())
 		call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 		call.AddArgs(callArgs...)
@@ -4956,10 +4958,12 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 		// call target
 		switch {
 		case k == callDefer:
-			aux := ssa.StaticAuxCall(ir.Syms.Deferproc, ACArgs, ACResults, nil) // TODO paramResultInfo for DeferProc
+			aux := ssa.StaticAuxCall(ir.Syms.Deferproc, ACArgs, ACResults,
+				s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults))) // TODO paramResultInfo for DeferProc
 			call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 		case k == callGo:
-			aux := ssa.StaticAuxCall(ir.Syms.Newproc, ACArgs, ACResults, nil)
+			aux := ssa.StaticAuxCall(ir.Syms.Newproc, ACArgs, ACResults,
+				s.f.ABIDefault.ABIAnalyzeTypes(nil, ssa.ACParamsToTypes(ACArgs), ssa.ACParamsToTypes(ACResults)))
 			call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux) // TODO paramResultInfo for NewProc
 		case closure != nil:
 			// rawLoad because loading the code pointer from a
@@ -5434,6 +5438,7 @@ func (s *state) rtcall(fn *obj.LSym, returns bool, results []*types.Type, args .
 	var ACArgs []ssa.Param
 	var ACResults []ssa.Param
 	var callArgs []*ssa.Value
+	var callArgTypes []*types.Type
 
 	for _, arg := range args {
 		t := arg.Type
@@ -5441,6 +5446,7 @@ func (s *state) rtcall(fn *obj.LSym, returns bool, results []*types.Type, args .
 		size := t.Size()
 		ACArgs = append(ACArgs, ssa.Param{Type: t, Offset: int32(off)})
 		callArgs = append(callArgs, arg)
+		callArgTypes = append(callArgTypes, t)
 		off += size
 	}
 	off = types.Rnd(off, int64(types.RegSize))
@@ -5455,7 +5461,7 @@ func (s *state) rtcall(fn *obj.LSym, returns bool, results []*types.Type, args .
 
 	// Issue call
 	var call *ssa.Value
-	aux := ssa.StaticAuxCall(fn, ACArgs, ACResults, nil) // WILL NEED A TYPE FOR THIS.)
+	aux := ssa.StaticAuxCall(fn, ACArgs, ACResults, s.f.ABIDefault.ABIAnalyzeTypes(nil, callArgTypes, results))
 	callArgs = append(callArgs, s.mem())
 	call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 	call.AddArgs(callArgs...)
@@ -6520,7 +6526,7 @@ func genssa(f *ssa.Func, pp *objw.Progs) {
 				// input args need no code
 			case ssa.OpSP, ssa.OpSB:
 				// nothing to do
-			case ssa.OpSelect0, ssa.OpSelect1:
+			case ssa.OpSelect0, ssa.OpSelect1, ssa.OpSelectN:
 				// nothing to do
 			case ssa.OpGetG:
 				// nothing to do when there's a g register,
diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index b6374e49a5..9fb6d68994 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -581,12 +581,19 @@ func NewTuple(t1, t2 *Type) *Type {
 	return t
 }
 
-func NewResults(types []*Type) *Type {
+func newResults(types []*Type) *Type {
 	t := New(TRESULTS)
 	t.Extra.(*Results).Types = types
 	return t
 }
 
+func NewResults(types []*Type) *Type {
+	if len(types) == 1 && types[0] == TypeMem {
+		return TypeResultMem
+	}
+	return newResults(types)
+}
+
 func newSSA(name string) *Type {
 	t := New(TSSA)
 	t.Extra = name
@@ -1407,6 +1414,9 @@ func (t *Type) PtrTo() *Type {
 }
 
 func (t *Type) NumFields() int {
+	if t.kind == TRESULTS {
+		return len(t.Extra.(*Results).Types)
+	}
 	return t.Fields().Len()
 }
 func (t *Type) FieldType(i int) *Type {
@@ -1597,11 +1607,12 @@ func FakeRecvType() *Type {
 
 var (
 	// TSSA types. HasPointers assumes these are pointer-free.
-	TypeInvalid = newSSA("invalid")
-	TypeMem     = newSSA("mem")
-	TypeFlags   = newSSA("flags")
-	TypeVoid    = newSSA("void")
-	TypeInt128  = newSSA("int128")
+	TypeInvalid   = newSSA("invalid")
+	TypeMem       = newSSA("mem")
+	TypeFlags     = newSSA("flags")
+	TypeVoid      = newSSA("void")
+	TypeInt128    = newSSA("int128")
+	TypeResultMem = newResults([]*Type{TypeMem})
 )
 
 // NewNamed returns a new named type for the given type name.