internal/abi, runtime, reflect, cmd: merge maxZero const into internal/abi

For #59670

Change-Id: If38a74ad067a3ea3ff551c0c25c8ef41abec114b
GitHub-Last-Rev: fb1f2f3c9f
GitHub-Pull-Request: golang/go#64268
Reviewed-on: https://go-review.googlesource.com/c/go/+/543655
Run-TryBot: qiulaidongfeng <2645477756@qq.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/walk/assign.go

@@ -6,6 +6,7 @@ package walk
 
 import (
 	"go/constant"
+	"internal/abi"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
@@ -168,7 +169,7 @@ func walkAssignMapRead(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
 	a := n.Lhs[0]
 
 	var call *ir.CallExpr
-	if w := t.Elem().Size(); w <= zeroValSize {
+	if w := t.Elem().Size(); w <= abi.ZeroValSize {
 		fn := mapfn(mapaccess2[fast], t, false)
 		call = mkcall1(fn, fn.Type().ResultsTuple(), init, reflectdata.IndexMapRType(base.Pos, r), r.X, key)
 	} else {

src/cmd/compile/internal/walk/expr.go

@@ -7,6 +7,7 @@ package walk
 import (
 	"fmt"
 	"go/constant"
+	"internal/abi"
 	"internal/buildcfg"
 	"strings"
 
@@ -825,7 +826,7 @@ func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
 	switch {
 	case n.Assigned:
 		mapFn = mapfn(mapassign[fast], t, false)
-	case t.Elem().Size() > zeroValSize:
+	case t.Elem().Size() > abi.ZeroValSize:
 		args = append(args, reflectdata.ZeroAddr(t.Elem().Size()))
 		mapFn = mapfn("mapaccess1_fat", t, true)
 	default:

src/cmd/compile/internal/walk/walk.go

@@ -18,7 +18,6 @@ import (
 
 // The constant is known to runtime.
 const tmpstringbufsize = 32
-const zeroValSize = 1024 // must match value of runtime/map.go:maxZero
 
 func Walk(fn *ir.Func) {
 	ir.CurFunc = fn

src/internal/abi/map.go

@@ -12,3 +12,6 @@ const (
 	MapMaxKeyBytes     = 128 // Must fit in a uint8.
 	MapMaxElemBytes    = 128 // Must fit in a uint8.
 )
+
+// ZeroValSize is the size in bytes of runtime.zeroVal.
+const ZeroValSize = 1024

src/reflect/value.go

@@ -1603,7 +1603,7 @@ func (v Value) IsZero() bool {
 		}
 		typ := (*abi.ArrayType)(unsafe.Pointer(v.typ()))
 		// If the type is comparable, then compare directly with zero.
-		if typ.Equal != nil && typ.Size() <= maxZero {
+		if typ.Equal != nil && typ.Size() <= abi.ZeroValSize {
 			// v.ptr doesn't escape, as Equal functions are compiler generated
 			// and never escape. The escape analysis doesn't know, as it is a
 			// function pointer call.
@@ -1631,7 +1631,7 @@ func (v Value) IsZero() bool {
 		}
 		typ := (*abi.StructType)(unsafe.Pointer(v.typ()))
 		// If the type is comparable, then compare directly with zero.
-		if typ.Equal != nil && typ.Size() <= maxZero {
+		if typ.Equal != nil && typ.Size() <= abi.ZeroValSize {
 			// See noescape justification above.
 			return typ.Equal(noescape(v.ptr), unsafe.Pointer(&zeroVal[0]))
 		}
@@ -3277,7 +3277,7 @@ func Zero(typ Type) Value {
 	fl := flag(t.Kind())
 	if t.IfaceIndir() {
 		var p unsafe.Pointer
-		if t.Size() <= maxZero {
+		if t.Size() <= abi.ZeroValSize {
 			p = unsafe.Pointer(&zeroVal[0])
 		} else {
 			p = unsafe_New(t)
@@ -3287,11 +3287,8 @@ func Zero(typ Type) Value {
 	return Value{t, nil, fl}
 }
 
-// must match declarations in runtime/map.go.
-const maxZero = 1024
-
 //go:linkname zeroVal runtime.zeroVal
-var zeroVal [maxZero]byte
+var zeroVal [abi.ZeroValSize]byte
 
 // New returns a Value representing a pointer to a new zero value
 // for the specified type. That is, the returned Value's Type is PointerTo(typ).

src/runtime/map.go

@@ -1436,8 +1436,7 @@ func reflectlite_maplen(h *hmap) int {
 	return h.count
 }
 
-const maxZero = 1024 // must match value in reflect/value.go:maxZero cmd/compile/internal/gc/walk.go:zeroValSize
-var zeroVal [maxZero]byte
+var zeroVal [abi.ZeroValSize]byte
 
 // mapinitnoop is a no-op function known the Go linker; if a given global
 // map (of the right size) is determined to be dead, the linker will