all: add GOOS=ios

Introduce GOOS=ios for iOS systems. GOOS=ios matches "darwin"
build tag, like GOOS=android matches "linux" and GOOS=illumos
matches "solaris". Only ios/arm64 is supported (ios/amd64 is
not).

GOOS=ios and GOOS=darwin remain essentially the same at this
point. They will diverge at later time, to differentiate macOS
and iOS.

Uses of GOOS=="darwin" are changed to (GOOS=="darwin" || GOOS=="ios"),
except if it clearly means macOS (e.g. GOOS=="darwin" && GOARCH=="amd64"),
it remains GOOS=="darwin".

Updates #38485.

Change-Id: I4faacdc1008f42434599efb3c3ad90763a83b67c
Reviewed-on: https://go-review.googlesource.com/c/go/+/254740
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

99 files changed, 215 insertions, 125 deletions

diff --git a/doc/install-source.html b/doc/install-source.html
index cbf4eac70b..86a4644c0c 100644
--- a/doc/install-source.html
+++ b/doc/install-source.html
@@ -507,8 +507,8 @@ These default to the values of <code>$GOHOSTOS</code> and
 
 <p>
 Choices for <code>$GOOS</code> are
-<code>android</code>, <code>darwin</code> (macOS/iOS),
-<code>dragonfly</code>, <code>freebsd</code>, <code>illumos</code>, <code>js</code>,
+<code>android</code>, <code>darwin</code>, <code>dragonfly</code>,
+<code>freebsd</code>, <code>illumos</code>, <code>ios</code>, <code>js</code>,
 <code>linux</code>, <code>netbsd</code>, <code>openbsd</code>,
 <code>plan9</code>, <code>solaris</code> and <code>windows</code>.
 </p>
@@ -567,6 +567,9 @@ The valid combinations of <code>$GOOS</code> and <code>$GOARCH</code> are:
 <td></td><td><code>illumos</code></td> <td><code>amd64</code></td>
 </tr>
 <tr>
+<td></td><td><code>ios</code></td> <td><code>arm64</code></td>
+</tr>
+<tr>
 <td></td><td><code>js</code></td> <td><code>wasm</code></td>
 </tr>
 <tr>
diff --git a/misc/cgo/test/issue18146.go b/misc/cgo/test/issue18146.go
index 196d98f507..f92d6c7f93 100644
--- a/misc/cgo/test/issue18146.go
+++ b/misc/cgo/test/issue18146.go
@@ -24,7 +24,7 @@ func test18146(t *testing.T) {
 		t.Skip("skipping in short mode")
 	}
 
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		t.Skipf("skipping flaky test on %s; see golang.org/issue/18202", runtime.GOOS)
 	}
 
diff --git a/misc/cgo/test/pkg_test.go b/misc/cgo/test/pkg_test.go
index 26c50ad883..a28ad4ea74 100644
--- a/misc/cgo/test/pkg_test.go
+++ b/misc/cgo/test/pkg_test.go
@@ -30,7 +30,7 @@ func TestCrossPackageTests(t *testing.T) {
 	switch runtime.GOOS {
 	case "android":
 		t.Skip("Can't exec cmd/go subprocess on Android.")
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			t.Skip("Can't exec cmd/go subprocess on iOS.")
diff --git a/misc/cgo/test/sigaltstack.go b/misc/cgo/test/sigaltstack.go
index 8dfa1cb5ad..27b753a147 100644
--- a/misc/cgo/test/sigaltstack.go
+++ b/misc/cgo/test/sigaltstack.go
@@ -62,7 +62,7 @@ import (
 
 func testSigaltstack(t *testing.T) {
 	switch {
-	case runtime.GOOS == "solaris", runtime.GOOS == "illumos", runtime.GOOS == "darwin" && runtime.GOARCH == "arm64":
+	case runtime.GOOS == "solaris", runtime.GOOS == "illumos", (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64":
 		t.Skipf("switching signal stack not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 
diff --git a/misc/cgo/test/test.go b/misc/cgo/test/test.go
index 05fa52b381..a78f88499b 100644
--- a/misc/cgo/test/test.go
+++ b/misc/cgo/test/test.go
@@ -1776,7 +1776,7 @@ func test14838(t *testing.T) {
 var sink C.int
 
 func test17065(t *testing.T) {
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		t.Skip("broken on darwin; issue 17065")
 	}
 	for i := range C.ii {
diff --git a/misc/cgo/test/testx.go b/misc/cgo/test/testx.go
index 7fbc5c64b3..2b2e69ec00 100644
--- a/misc/cgo/test/testx.go
+++ b/misc/cgo/test/testx.go
@@ -164,7 +164,7 @@ func Add(x int) {
 }
 
 func testCthread(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skip("the iOS exec wrapper is unable to properly handle the panic from Add")
 	}
 	sum.i = 0
diff --git a/misc/cgo/testcarchive/carchive_test.go b/misc/cgo/testcarchive/carchive_test.go
index b4a046c4bc..2e223ea369 100644
--- a/misc/cgo/testcarchive/carchive_test.go
+++ b/misc/cgo/testcarchive/carchive_test.go
@@ -118,9 +118,9 @@ func testMain(m *testing.M) int {
 		cc = append(cc, s[start:])
 	}
 
-	if GOOS == "darwin" {
+	if GOOS == "darwin" || GOOS == "ios" {
 		// For Darwin/ARM.
-		// TODO(crawshaw): can we do better?
+		// TODO: do we still need this?
 		cc = append(cc, []string{"-framework", "CoreFoundation", "-framework", "Foundation"}...)
 	}
 	if GOOS == "aix" {
@@ -133,7 +133,7 @@ func testMain(m *testing.M) int {
 		libbase = "gccgo_" + libgodir + "_fPIC"
 	} else {
 		switch GOOS {
-		case "darwin":
+		case "darwin", "ios":
 			if GOARCH == "arm64" {
 				libbase += "_shared"
 			}
@@ -303,7 +303,7 @@ func TestInstall(t *testing.T) {
 
 func TestEarlySignalHandler(t *testing.T) {
 	switch GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		switch GOARCH {
 		case "arm64":
 			t.Skipf("skipping on %s/%s; see https://golang.org/issue/13701", GOOS, GOARCH)
@@ -384,7 +384,7 @@ func TestSignalForwarding(t *testing.T) {
 	expectSignal(t, err, syscall.SIGSEGV)
 
 	// SIGPIPE is never forwarded on darwin. See golang.org/issue/33384.
-	if runtime.GOOS != "darwin" {
+	if runtime.GOOS != "darwin" && runtime.GOOS != "ios" {
 		// Test SIGPIPE forwarding
 		cmd = exec.Command(bin[0], append(bin[1:], "3")...)
 
@@ -485,7 +485,7 @@ func TestSignalForwardingExternal(t *testing.T) {
 // doesn't work on this platform.
 func checkSignalForwardingTest(t *testing.T) {
 	switch GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		switch GOARCH {
 		case "arm64":
 			t.Skipf("skipping on %s/%s; see https://golang.org/issue/13701", GOOS, GOARCH)
@@ -603,7 +603,7 @@ func TestExtar(t *testing.T) {
 	if runtime.Compiler == "gccgo" {
 		t.Skip("skipping -extar test when using gccgo")
 	}
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skip("shell scripts are not executable on iOS hosts")
 	}
 
@@ -645,7 +645,7 @@ func TestExtar(t *testing.T) {
 
 func TestPIE(t *testing.T) {
 	switch GOOS {
-	case "windows", "darwin", "plan9":
+	case "windows", "darwin", "ios", "plan9":
 		t.Skipf("skipping PIE test on %s", GOOS)
 	}
 
@@ -738,7 +738,7 @@ func TestSIGPROF(t *testing.T) {
 	switch GOOS {
 	case "windows", "plan9":
 		t.Skipf("skipping SIGPROF test on %s", GOOS)
-	case "darwin":
+	case "darwin", "ios":
 		t.Skipf("skipping SIGPROF test on %s; see https://golang.org/issue/19320", GOOS)
 	}
 
@@ -841,7 +841,7 @@ func TestCompileWithoutShared(t *testing.T) {
 	expectSignal(t, err, syscall.SIGSEGV)
 
 	// SIGPIPE is never forwarded on darwin. See golang.org/issue/33384.
-	if runtime.GOOS != "darwin" {
+	if runtime.GOOS != "darwin" && runtime.GOOS != "ios" {
 		binArgs := append(cmdToRun(exe), "3")
 		t.Log(binArgs)
 		out, err = exec.Command(binArgs[0], binArgs[1:]...).CombinedOutput()
diff --git a/misc/cgo/testcshared/cshared_test.go b/misc/cgo/testcshared/cshared_test.go
index bd4d341820..d557f34b0f 100644
--- a/misc/cgo/testcshared/cshared_test.go
+++ b/misc/cgo/testcshared/cshared_test.go
@@ -98,7 +98,7 @@ func testMain(m *testing.M) int {
 	}
 
 	switch GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		// For Darwin/ARM.
 		// TODO(crawshaw): can we do better?
 		cc = append(cc, []string{"-framework", "CoreFoundation", "-framework", "Foundation"}...)
@@ -107,7 +107,7 @@ func testMain(m *testing.M) int {
 	}
 	libgodir := GOOS + "_" + GOARCH
 	switch GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		if GOARCH == "arm64" {
 			libgodir += "_shared"
 		}
@@ -407,7 +407,7 @@ func TestUnexportedSymbols(t *testing.T) {
 	adbPush(t, libname)
 
 	linkFlags := "-Wl,--no-as-needed"
-	if GOOS == "darwin" {
+	if GOOS == "darwin" || GOOS == "ios" {
 		linkFlags = ""
 	}
 
@@ -636,7 +636,7 @@ func copyFile(t *testing.T, dst, src string) {
 
 func TestGo2C2Go(t *testing.T) {
 	switch GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		// Darwin shared libraries don't support the multiple
 		// copies of the runtime package implied by this test.
 		t.Skip("linking c-shared into Go programs not supported on Darwin; issue 29061")
diff --git a/misc/cgo/testso/so_test.go b/misc/cgo/testso/so_test.go
index bdd6bd8468..57f0fd34f7 100644
--- a/misc/cgo/testso/so_test.go
+++ b/misc/cgo/testso/so_test.go
@@ -21,7 +21,7 @@ func requireTestSOSupported(t *testing.T) {
 	t.Helper()
 	switch runtime.GOARCH {
 	case "arm64":
-		if runtime.GOOS == "darwin" {
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 			t.Skip("No exec facility on iOS.")
 		}
 	case "ppc64":
@@ -74,7 +74,7 @@ func TestSO(t *testing.T) {
 	ext := "so"
 	args := append(gogccflags, "-shared")
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		ext = "dylib"
 		args = append(args, "-undefined", "suppress", "-flat_namespace")
 	case "windows":
@@ -119,7 +119,7 @@ func TestSO(t *testing.T) {
 	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
 	if runtime.GOOS != "windows" {
 		s := "LD_LIBRARY_PATH"
-		if runtime.GOOS == "darwin" {
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 			s = "DYLD_LIBRARY_PATH"
 		}
 		cmd.Env = append(os.Environ(), s+"=.")
diff --git a/misc/cgo/testsovar/so_test.go b/misc/cgo/testsovar/so_test.go
index bdd6bd8468..57f0fd34f7 100644
--- a/misc/cgo/testsovar/so_test.go
+++ b/misc/cgo/testsovar/so_test.go
@@ -21,7 +21,7 @@ func requireTestSOSupported(t *testing.T) {
 	t.Helper()
 	switch runtime.GOARCH {
 	case "arm64":
-		if runtime.GOOS == "darwin" {
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 			t.Skip("No exec facility on iOS.")
 		}
 	case "ppc64":
@@ -74,7 +74,7 @@ func TestSO(t *testing.T) {
 	ext := "so"
 	args := append(gogccflags, "-shared")
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		ext = "dylib"
 		args = append(args, "-undefined", "suppress", "-flat_namespace")
 	case "windows":
@@ -119,7 +119,7 @@ func TestSO(t *testing.T) {
 	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
 	if runtime.GOOS != "windows" {
 		s := "LD_LIBRARY_PATH"
-		if runtime.GOOS == "darwin" {
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 			s = "DYLD_LIBRARY_PATH"
 		}
 		cmd.Env = append(os.Environ(), s+"=.")
diff --git a/src/archive/tar/stat_unix.go b/src/archive/tar/stat_unix.go
index d1576db41d..8df3616990 100644
--- a/src/archive/tar/stat_unix.go
+++ b/src/archive/tar/stat_unix.go
@@ -66,7 +66,7 @@ func statUnix(fi os.FileInfo, h *Header) error {
 			minor := uint32((dev & 0x00000000000000ff) >> 0)
 			minor |= uint32((dev & 0x00000ffffff00000) >> 12)
 			h.Devmajor, h.Devminor = int64(major), int64(minor)
-		case "darwin":
+		case "darwin", "ios":
 			// Copied from golang.org/x/sys/unix/dev_darwin.go.
 			major := uint32((dev >> 24) & 0xff)
 			minor := uint32(dev & 0xffffff)
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 730db44990..111a309eb5 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -298,7 +298,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 			continue
 		}
 
-		if goos == "darwin" && strings.HasSuffix(n.C, "Ref") {
+		if (goos == "darwin" || goos == "ios") && strings.HasSuffix(n.C, "Ref") {
 			// For FooRef, find out if FooGetTypeID exists.
 			s := n.C[:len(n.C)-3] + "GetTypeID"
 			n := &Name{Go: s, C: s}
@@ -3075,7 +3075,7 @@ func (c *typeConv) badCFType(dt *dwarf.TypedefType) bool {
 	// We identify the correct set of types as those ending in Ref and for which
 	// there exists a corresponding GetTypeID function.
 	// See comment below for details about the bad pointers.
-	if goos != "darwin" {
+	if goos != "darwin" && goos != "ios" {
 		return false
 	}
 	s := dt.Name
diff --git a/src/cmd/compile/internal/arm64/ggen.go b/src/cmd/compile/internal/arm64/ggen.go
index f698919e9b..f3fec03854 100644
--- a/src/cmd/compile/internal/arm64/ggen.go
+++ b/src/cmd/compile/internal/arm64/ggen.go
@@ -11,7 +11,7 @@ import (
 	"cmd/internal/objabi"
 )
 
-var darwin = objabi.GOOS == "darwin"
+var darwin = objabi.GOOS == "darwin" || objabi.GOOS == "ios"
 
 func padframe(frame int64) int64 {
 	// arm64 requires that the frame size (not counting saved FP&LR)
diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 4b2f06def1..7f01f8047f 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -248,7 +248,7 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize bool) *Config
 		c.FPReg = framepointerRegARM64
 		c.LinkReg = linkRegARM64
 		c.hasGReg = true
-		c.noDuffDevice = objabi.GOOS == "darwin" // darwin linker cannot handle BR26 reloc with non-zero addend
+		c.noDuffDevice = objabi.GOOS == "darwin" || objabi.GOOS == "ios" // darwin linker cannot handle BR26 reloc with non-zero addend
 	case "ppc64":
 		c.BigEndian = true
 		fallthrough
diff --git a/src/cmd/dist/build.go b/src/cmd/dist/build.go
index 397b3bb88f..3ac742fa55 100644
--- a/src/cmd/dist/build.go
+++ b/src/cmd/dist/build.go
@@ -80,6 +80,7 @@ var okgoos = []string{
 	"darwin",
 	"dragonfly",
 	"illumos",
+	"ios",
 	"js",
 	"linux",
 	"android",
@@ -970,7 +971,10 @@ func matchtag(tag string) bool {
 		}
 		return !matchtag(tag[1:])
 	}
-	return tag == "gc" || tag == goos || tag == goarch || tag == "cmd_go_bootstrap" || tag == "go1.1" || (goos == "android" && tag == "linux") || (goos == "illumos" && tag == "solaris")
+	return tag == "gc" || tag == goos || tag == goarch || tag == "cmd_go_bootstrap" || tag == "go1.1" ||
+		(goos == "android" && tag == "linux") ||
+		(goos == "illumos" && tag == "solaris") ||
+		(goos == "ios" && tag == "darwin")
 }
 
 // shouldbuild reports whether we should build this file.
@@ -984,7 +988,7 @@ func shouldbuild(file, pkg string) bool {
 	name := filepath.Base(file)
 	excluded := func(list []string, ok string) bool {
 		for _, x := range list {
-			if x == ok || (ok == "android" && x == "linux") || (ok == "illumos" && x == "solaris") {
+			if x == ok || (ok == "android" && x == "linux") || (ok == "illumos" && x == "solaris") || (ok == "ios" && x == "darwin") {
 				continue
 			}
 			i := strings.Index(name, x)
@@ -1462,7 +1466,7 @@ func wrapperPathFor(goos, goarch string) string {
 		if gohostos != "android" {
 			return pathf("%s/misc/android/go_android_exec.go", goroot)
 		}
-	case goos == "darwin" && goarch == "arm64":
+	case (goos == "darwin" || goos == "ios") && goarch == "arm64":
 		if gohostos != "darwin" || gohostarch != "arm64" {
 			return pathf("%s/misc/ios/go_darwin_arm_exec.go", goroot)
 		}
@@ -1541,6 +1545,7 @@ var cgoEnabled = map[string]bool{
 	"android/amd64":   true,
 	"android/arm":     true,
 	"android/arm64":   true,
+	"ios/arm64":       true,
 	"js/wasm":         false,
 	"netbsd/386":      true,
 	"netbsd/amd64":    true,
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index 5ea5c81656..f953a76963 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -464,7 +464,7 @@ func (t *tester) registerTests() {
 	}
 
 	// Test the ios build tag on darwin/amd64 for the iOS simulator.
-	if goos == "darwin" && !t.iOS() {
+	if goos == "darwin" && goarch == "amd64" {
 		t.tests = append(t.tests, distTest{
 			name:    "amd64ios",
 			heading: "ios tag on darwin/amd64",
@@ -903,7 +903,7 @@ func (t *tester) addCmd(dt *distTest, dir string, cmdline ...interface{}) *exec.
 }
 
 func (t *tester) iOS() bool {
-	return goos == "darwin" && goarch == "arm64"
+	return (goos == "darwin" || goos == "ios") && goarch == "arm64"
 }
 
 func (t *tester) out(v string) {
@@ -943,7 +943,10 @@ func (t *tester) internalLink() bool {
 	if goos == "android" {
 		return false
 	}
-	if t.iOS() {
+	if goos == "ios" {
+		return false
+	}
+	if goos == "darwin" && goarch == "arm64" {
 		return false
 	}
 	// Internally linking cgo is incomplete on some architectures.
diff --git a/src/cmd/doc/doc_test.go b/src/cmd/doc/doc_test.go
index f13d917634..47602833d3 100644
--- a/src/cmd/doc/doc_test.go
+++ b/src/cmd/doc/doc_test.go
@@ -36,8 +36,8 @@ func TestMain(m *testing.M) {
 }
 
 func maybeSkip(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
-		t.Skip("darwin/arm64 does not have a full file tree")
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
+		t.Skip("iOS does not have a full file tree")
 	}
 }
 
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 804ca9e5a5..4bc87008ff 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -1608,6 +1608,9 @@
 // Using GOOS=illumos matches build tags and files as for GOOS=solaris
 // in addition to illumos tags and files.
 //
+// Using GOOS=ios matches build tags and files as for GOOS=darwin
+// in addition to ios tags and files.
+//
 // To keep a file from being considered for the build:
 //
 // 	// +build ignore
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 021930a8a8..66a52c86ad 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -58,7 +58,7 @@ func init() {
 	switch runtime.GOOS {
 	case "android", "js":
 		canRun = false
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			canRun = false
diff --git a/src/cmd/go/internal/bug/bug.go b/src/cmd/go/internal/bug/bug.go
index 52bd40f2fb..07e3516855 100644
--- a/src/cmd/go/internal/bug/bug.go
+++ b/src/cmd/go/internal/bug/bug.go
@@ -105,7 +105,7 @@ func printGoDetails(w io.Writer) {
 
 func printOSDetails(w io.Writer) {
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		printCmdOut(w, "uname -v: ", "uname", "-v")
 		printCmdOut(w, "", "sw_vers")
 	case "linux":
diff --git a/src/cmd/go/internal/help/helpdoc.go b/src/cmd/go/internal/help/helpdoc.go
index e1f0521ea4..0ae5fd7ca9 100644
--- a/src/cmd/go/internal/help/helpdoc.go
+++ b/src/cmd/go/internal/help/helpdoc.go
@@ -838,6 +838,9 @@ in addition to android tags and files.
 Using GOOS=illumos matches build tags and files as for GOOS=solaris
 in addition to illumos tags and files.
 
+Using GOOS=ios matches build tags and files as for GOOS=darwin
+in addition to ios tags and files.
+
 To keep a file from being considered for the build:
 
 	// +build ignore
diff --git a/src/cmd/go/internal/imports/build.go b/src/cmd/go/internal/imports/build.go
index eb070eef4c..50aeabc578 100644
--- a/src/cmd/go/internal/imports/build.go
+++ b/src/cmd/go/internal/imports/build.go
@@ -141,6 +141,9 @@ func matchTag(name string, tags map[string]bool, want bool) bool {
 	if name == "solaris" {
 		have = have || tags["illumos"]
 	}
+	if name == "darwin" {
+		have = have || tags["ios"]
+	}
 	return have == want
 }
 
@@ -158,6 +161,7 @@ func matchTag(name string, tags map[string]bool, want bool) bool {
 // Exceptions:
 //     if GOOS=android, then files with GOOS=linux are also matched.
 //     if GOOS=illumos, then files with GOOS=solaris are also matched.
+//     if GOOS=ios, then files with GOOS=darwin are also matched.
 //
 // If tags["*"] is true, then MatchFile will consider all possible
 // GOOS and GOARCH to be available and will consequently
@@ -208,6 +212,7 @@ var KnownOS = map[string]bool{
 	"freebsd":   true,
 	"hurd":      true,
 	"illumos":   true,
+	"ios":       true,
 	"js":        true,
 	"linux":     true,
 	"nacl":      true, // legacy; don't remove
diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 1cbd7962e7..5cc77915e7 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -1950,7 +1950,7 @@ func externalLinkingForced(p *Package) bool {
 		if cfg.BuildContext.GOARCH != "arm64" {
 			return true
 		}
-	case "darwin":
+	case "darwin", "ios":
 		if cfg.BuildContext.GOARCH == "arm64" {
 			return true
 		}
diff --git a/src/cmd/go/internal/work/build_test.go b/src/cmd/go/internal/work/build_test.go
index c33de2635d..afed0fba72 100644
--- a/src/cmd/go/internal/work/build_test.go
+++ b/src/cmd/go/internal/work/build_test.go
@@ -221,7 +221,7 @@ func pkgImportPath(pkgpath string) *load.Package {
 // See https://golang.org/issue/18878.
 func TestRespectSetgidDir(t *testing.T) {
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		if runtime.GOARCH == "arm64" {
 			t.Skip("can't set SetGID bit with chmod on iOS")
 		}
diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index afd6fd6d3f..51fc2b588d 100644
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -2424,7 +2424,7 @@ func (b *Builder) compilerCmd(compiler []string, incdir, workdir string) []strin
 	// On OS X, some of the compilers behave as if -fno-common
 	// is always set, and the Mach-O linker in 6l/8l assumes this.
 	// See https://golang.org/issue/3253.
-	if cfg.Goos == "darwin" {
+	if cfg.Goos == "darwin" || cfg.Goos == "ios" {
 		a = append(a, "-fno-common")
 	}
 
diff --git a/src/cmd/go/internal/work/init.go b/src/cmd/go/internal/work/init.go
index 42692acd3b..b0d6133768 100644
--- a/src/cmd/go/internal/work/init.go
+++ b/src/cmd/go/internal/work/init.go
@@ -121,7 +121,7 @@ func buildModeInit() {
 			codegenArg = "-fPIC"
 		} else {
 			switch cfg.Goos {
-			case "darwin":
+			case "darwin", "ios":
 				switch cfg.Goarch {
 				case "arm64":
 					codegenArg = "-shared"
@@ -157,7 +157,7 @@ func buildModeInit() {
 			ldBuildmode = "pie"
 		case "windows":
 			ldBuildmode = "pie"
-		case "darwin":
+		case "darwin", "ios":
 			switch cfg.Goarch {
 			case "arm64":
 				codegenArg = "-shared"
diff --git a/src/cmd/internal/archive/archive_test.go b/src/cmd/internal/archive/archive_test.go
index 1468a58210..cb4eb842b4 100644
--- a/src/cmd/internal/archive/archive_test.go
+++ b/src/cmd/internal/archive/archive_test.go
@@ -243,7 +243,7 @@ func TestParseCGOArchive(t *testing.T) {
 	c1 := "c1"
 	c2 := "c2"
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		c1 = "_" + c1
 		c2 = "_" + c2
 	case "windows":
@@ -275,7 +275,7 @@ func TestParseCGOArchive(t *testing.T) {
 
 		obj := io.NewSectionReader(f, e.Offset, e.Size)
 		switch runtime.GOOS {
-		case "darwin":
+		case "darwin", "ios":
 			mf, err := macho.NewFile(obj)
 			if err != nil {
 				t.Fatal(err)
diff --git a/src/cmd/internal/dwarf/dwarf.go b/src/cmd/internal/dwarf/dwarf.go
index 6ab83639ac..b2fd5262bb 100644
--- a/src/cmd/internal/dwarf/dwarf.go
+++ b/src/cmd/internal/dwarf/dwarf.go
@@ -378,7 +378,7 @@ func expandPseudoForm(form uint8) uint8 {
 		return form
 	}
 	expandedForm := DW_FORM_udata
-	if objabi.GOOS == "darwin" {
+	if objabi.GOOS == "darwin" || objabi.GOOS == "ios" {
 		expandedForm = DW_FORM_data4
 	}
 	return uint8(expandedForm)
diff --git a/src/cmd/internal/objabi/head.go b/src/cmd/internal/objabi/head.go
index 95b8db3809..48ff292307 100644
--- a/src/cmd/internal/objabi/head.go
+++ b/src/cmd/internal/objabi/head.go
@@ -54,7 +54,7 @@ func (h *HeadType) Set(s string) error {
 	switch s {
 	case "aix":
 		*h = Haix
-	case "darwin":
+	case "darwin", "ios":
 		*h = Hdarwin
 	case "dragonfly":
 		*h = Hdragonfly
diff --git a/src/cmd/internal/objabi/util.go b/src/cmd/internal/objabi/util.go
index d2d6fdbda8..b81b73a022 100644
--- a/src/cmd/internal/objabi/util.go
+++ b/src/cmd/internal/objabi/util.go
@@ -139,7 +139,7 @@ func init() {
 }
 
 // Note: must agree with runtime.framepointer_enabled.
-var Framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" && (GOOS == "linux" || GOOS == "darwin")
+var Framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" && (GOOS == "linux" || GOOS == "darwin" || GOOS == "ios")
 
 func addexp(s string) {
 	// Could do general integer parsing here, but the runtime copy doesn't yet.
diff --git a/src/cmd/internal/sys/supported.go b/src/cmd/internal/sys/supported.go
index c27b3b986d..b2b3b02bf6 100644
--- a/src/cmd/internal/sys/supported.go
+++ b/src/cmd/internal/sys/supported.go
@@ -38,7 +38,7 @@ func MustLinkExternal(goos, goarch string) bool {
 		if goarch != "arm64" {
 			return true
 		}
-	case "darwin":
+	case "darwin", "ios":
 		if goarch == "arm64" {
 			return true
 		}
diff --git a/src/cmd/link/internal/ld/ar.go b/src/cmd/link/internal/ld/ar.go
index 52adbc3bab..e4fd591676 100644
--- a/src/cmd/link/internal/ld/ar.go
+++ b/src/cmd/link/internal/ld/ar.go
@@ -170,7 +170,7 @@ func readArmap(filename string, f *bio.Reader, arhdr ArHdr) archiveMap {
 
 		// For Mach-O and PE/386 files we strip a leading
 		// underscore from the symbol name.
-		if objabi.GOOS == "darwin" || (objabi.GOOS == "windows" && objabi.GOARCH == "386") {
+		if objabi.GOOS == "darwin" || objabi.GOOS == "ios" || (objabi.GOOS == "windows" && objabi.GOARCH == "386") {
 			if name[0] == '_' && len(name) > 1 {
 				name = name[1:]
 			}
diff --git a/src/cmd/link/internal/ld/config.go b/src/cmd/link/internal/ld/config.go
index 2373b500e3..9aa59fa3e3 100644
--- a/src/cmd/link/internal/ld/config.go
+++ b/src/cmd/link/internal/ld/config.go
@@ -51,7 +51,7 @@ func (mode *BuildMode) Set(s string) error {
 		*mode = BuildModePIE
 	case "c-archive":
 		switch objabi.GOOS {
-		case "aix", "darwin", "linux":
+		case "aix", "darwin", "ios", "linux":
 		case "freebsd":
 			switch objabi.GOARCH {
 			case "amd64":
diff --git a/src/cmd/link/internal/ld/outbuf_test.go b/src/cmd/link/internal/ld/outbuf_test.go
index db0a92485e..e6643da396 100644
--- a/src/cmd/link/internal/ld/outbuf_test.go
+++ b/src/cmd/link/internal/ld/outbuf_test.go
@@ -17,7 +17,7 @@ func TestMMap(t *testing.T) {
 	switch runtime.GOOS {
 	default:
 		t.Skip("unsupported OS")
-	case "aix", "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "windows":
+	case "aix", "darwin", "ios", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "windows":
 	}
 	dir, err := ioutil.TempDir("", "TestMMap")
 	if err != nil {
diff --git a/src/cmd/nm/nm_test.go b/src/cmd/nm/nm_test.go
index 5d7fff0f99..413a4eb06f 100644
--- a/src/cmd/nm/nm_test.go
+++ b/src/cmd/nm/nm_test.go
@@ -283,7 +283,7 @@ func testGoLib(t *testing.T, iscgo bool) {
 	if iscgo {
 		syms = append(syms, symType{"B", "mylib.TestCgodata", false, false})
 		syms = append(syms, symType{"T", "mylib.TestCgofunc", false, false})
-		if runtime.GOOS == "darwin" || (runtime.GOOS == "windows" && runtime.GOARCH == "386") {
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" || (runtime.GOOS == "windows" && runtime.GOARCH == "386") {
 			syms = append(syms, symType{"D", "_cgodata", true, false})
 			syms = append(syms, symType{"T", "_cgofunc", true, false})
 		} else if runtime.GOOS == "aix" {
diff --git a/src/crypto/x509/root_darwin_ios_gen.go b/src/crypto/x509/root_darwin_ios_gen.go
index 7a42466e5f..61152b4d11 100644
--- a/src/crypto/x509/root_darwin_ios_gen.go
+++ b/src/crypto/x509/root_darwin_ios_gen.go
@@ -4,7 +4,7 @@
 
 // +build ignore
 
-// Generates root_darwin_ios.go.
+// Generates root_darwin_iosx.go.
 //
 // As of iOS 13, there is no API for querying the system trusted X.509 root
 // certificates.
@@ -37,7 +37,10 @@ import (
 )
 
 func main() {
-	var output = flag.String("output", "root_darwin_ios.go", "file name to write")
+	// Temporarily name the file _iosx.go, to avoid restricting it to GOOS=ios,
+	// as this is also used for darwin/arm64 (macOS).
+	// TODO: maybe use darwin/amd64 implementation on macOS arm64?
+	var output = flag.String("output", "root_darwin_iosx.go", "file name to write")
 	var version = flag.String("version", "", "security_certificates version")
 	flag.Parse()
 	if *version == "" {
diff --git a/src/crypto/x509/root_darwin_ios.go b/src/crypto/x509/root_darwin_iosx.go
index 5ecc4911b3..5ecc4911b3 100644
--- a/src/crypto/x509/root_darwin_ios.go
+++ b/src/crypto/x509/root_darwin_iosx.go
diff --git a/src/debug/elf/file_test.go b/src/debug/elf/file_test.go
index 24948e696a..4c6fdeece9 100644
--- a/src/debug/elf/file_test.go
+++ b/src/debug/elf/file_test.go
@@ -899,7 +899,7 @@ func TestCompressedSection(t *testing.T) {
 func TestNoSectionOverlaps(t *testing.T) {
 	// Ensure cmd/link outputs sections without overlaps.
 	switch runtime.GOOS {
-	case "aix", "android", "darwin", "js", "plan9", "windows":
+	case "aix", "android", "darwin", "ios", "js", "plan9", "windows":
 		t.Skipf("cmd/link doesn't produce ELF binaries on %s", runtime.GOOS)
 	}
 	_ = net.ResolveIPAddr // force dynamic linkage
diff --git a/src/go/build/build.go b/src/go/build/build.go
index 6b75aad9cf..5c3d876130 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -1754,6 +1754,9 @@ func (ctxt *Context) match(name string, allTags map[string]bool) bool {
 	if ctxt.GOOS == "illumos" && name == "solaris" {
 		return true
 	}
+	if ctxt.GOOS == "ios" && name == "darwin" {
+		return true
+	}
 
 	// other tags
 	for _, tag := range ctxt.BuildTags {
@@ -1781,7 +1784,10 @@ func (ctxt *Context) match(name string, allTags map[string]bool) bool {
 //     name_$(GOARCH)_test.*
 //     name_$(GOOS)_$(GOARCH)_test.*
 //
-// An exception: if GOOS=android, then files with GOOS=linux are also matched.
+// Exceptions:
+// if GOOS=android, then files with GOOS=linux are also matched.
+// if GOOS=illumos, then files with GOOS=solaris are also matched.
+// if GOOS=ios, then files with GOOS=darwin are also matched.
 func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
 	if dot := strings.Index(name, "."); dot != -1 {
 		name = name[:dot]
diff --git a/src/go/build/build_test.go b/src/go/build/build_test.go
index a7f2a3e902..22c62ce87d 100644
--- a/src/go/build/build_test.go
+++ b/src/go/build/build_test.go
@@ -120,7 +120,7 @@ func TestMultiplePackageImport(t *testing.T) {
 }
 
 func TestLocalDirectory(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skipf("skipping on %s/%s, no valid GOROOT", runtime.GOOS, runtime.GOARCH)
 	}
 
@@ -250,7 +250,7 @@ func TestMatchFile(t *testing.T) {
 }
 
 func TestImportCmd(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skipf("skipping on %s/%s, no valid GOROOT", runtime.GOOS, runtime.GOARCH)
 	}
 
diff --git a/src/go/build/syslist.go b/src/go/build/syslist.go
index fbfe4c4677..1275f7c986 100644
--- a/src/go/build/syslist.go
+++ b/src/go/build/syslist.go
@@ -7,5 +7,5 @@ package build
 // List of past, present, and future known GOOS and GOARCH values.
 // Do not remove from this list, as these are used for go/build filename matching.
 
-const goosList = "aix android darwin dragonfly freebsd hurd illumos js linux nacl netbsd openbsd plan9 solaris windows zos "
+const goosList = "aix android darwin dragonfly freebsd hurd illumos ios js linux nacl netbsd openbsd plan9 solaris windows zos "
 const goarchList = "386 amd64 amd64p32 arm armbe arm64 arm64be ppc64 ppc64le mips mipsle mips64 mips64le mips64p32 mips64p32le ppc riscv riscv64 s390 s390x sparc sparc64 wasm "
diff --git a/src/go/build/syslist_test.go b/src/go/build/syslist_test.go
index 7973ff4ee5..2b7b4c71aa 100644
--- a/src/go/build/syslist_test.go
+++ b/src/go/build/syslist_test.go
@@ -17,7 +17,7 @@ var (
 )
 
 func anotherOS() string {
-	if thisOS != "darwin" {
+	if thisOS != "darwin" && thisOS != "ios" {
 		return "darwin"
 	}
 	return "linux"
diff --git a/src/internal/poll/read_test.go b/src/internal/poll/read_test.go
index b4f5236d3e..2d4ef97da0 100644
--- a/src/internal/poll/read_test.go
+++ b/src/internal/poll/read_test.go
@@ -38,7 +38,7 @@ func TestRead(t *testing.T) {
 func specialFiles() []string {
 	var ps []string
 	switch runtime.GOOS {
-	case "darwin", "dragonfly", "freebsd", "netbsd", "openbsd":
+	case "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd":
 		ps = []string{
 			"/dev/null",
 		}
diff --git a/src/internal/testenv/testenv.go b/src/internal/testenv/testenv.go
index 309b2702ed..cfb033b2a2 100644
--- a/src/internal/testenv/testenv.go
+++ b/src/internal/testenv/testenv.go
@@ -45,7 +45,7 @@ func HasGoBuild() bool {
 	switch runtime.GOOS {
 	case "android", "js":
 		return false
-	case "darwin":
+	case "darwin", "ios":
 		if runtime.GOARCH == "arm64" {
 			return false
 		}
@@ -124,7 +124,7 @@ func HasExec() bool {
 	switch runtime.GOOS {
 	case "js":
 		return false
-	case "darwin":
+	case "darwin", "ios":
 		if runtime.GOARCH == "arm64" {
 			return false
 		}
@@ -135,7 +135,7 @@ func HasExec() bool {
 // HasSrc reports whether the entire source tree is available under GOROOT.
 func HasSrc() bool {
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		if runtime.GOARCH == "arm64" {
 			return false
 		}
diff --git a/src/log/syslog/syslog_test.go b/src/log/syslog/syslog_test.go
index f778e965f3..dd2f83e04f 100644
--- a/src/log/syslog/syslog_test.go
+++ b/src/log/syslog/syslog_test.go
@@ -51,7 +51,7 @@ func testableNetwork(network string) bool {
 	switch network {
 	case "unix", "unixgram":
 		switch runtime.GOOS {
-		case "darwin":
+		case "darwin", "ios":
 			switch runtime.GOARCH {
 			case "arm64":
 				return false
diff --git a/src/net/conf.go b/src/net/conf.go
index 971b1a399a..5340847123 100644
--- a/src/net/conf.go
+++ b/src/net/conf.go
@@ -69,7 +69,7 @@ func initConfVal() {
 	// Darwin pops up annoying dialog boxes if programs try to do
 	// their own DNS requests. So always use cgo instead, which
 	// avoids that.
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		confVal.forceCgoLookupHost = true
 		return
 	}
diff --git a/src/net/dial_test.go b/src/net/dial_test.go
index 01582489de..2706de4442 100644
--- a/src/net/dial_test.go
+++ b/src/net/dial_test.go
@@ -160,7 +160,7 @@ func dialClosedPort(t *testing.T) (actual, expected time.Duration) {
 	// but other platforms should be instantaneous.
 	if runtime.GOOS == "windows" {
 		expected = 1500 * time.Millisecond
-	} else if runtime.GOOS == "darwin" {
+	} else if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		expected = 150 * time.Millisecond
 	} else {
 		expected = 95 * time.Millisecond
@@ -990,7 +990,7 @@ func TestDialerControl(t *testing.T) {
 // except that it won't skip testing on non-mobile builders.
 func mustHaveExternalNetwork(t *testing.T) {
 	t.Helper()
-	mobile := runtime.GOOS == "android" || runtime.GOOS == "darwin" && runtime.GOARCH == "arm64"
+	mobile := runtime.GOOS == "android" || (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64"
 	if testenv.Builder() == "" || mobile {
 		testenv.MustHaveExternalNetwork(t)
 	}
diff --git a/src/net/http/cgi/host.go b/src/net/http/cgi/host.go
index 863f40638a..624044aa09 100644
--- a/src/net/http/cgi/host.go
+++ b/src/net/http/cgi/host.go
@@ -37,7 +37,7 @@ var trailingPort = regexp.MustCompile(`:([0-9]+)$`)
 
 var osDefaultInheritEnv = func() []string {
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		return []string{"DYLD_LIBRARY_PATH"}
 	case "linux", "freebsd", "openbsd":
 		return []string{"LD_LIBRARY_PATH"}
diff --git a/src/net/interface_unix_test.go b/src/net/interface_unix_test.go
index 6a2b7f1a88..bf41a0fb82 100644
--- a/src/net/interface_unix_test.go
+++ b/src/net/interface_unix_test.go
@@ -46,7 +46,7 @@ func TestPointToPointInterface(t *testing.T) {
 	if testing.Short() {
 		t.Skip("avoid external network")
 	}
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if os.Getuid() != 0 {
diff --git a/src/net/lookup_test.go b/src/net/lookup_test.go
index 68bffcab8f..32a0d377da 100644
--- a/src/net/lookup_test.go
+++ b/src/net/lookup_test.go
@@ -511,7 +511,7 @@ func TestDNSFlood(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 
 	var N = 5000
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		// On Darwin this test consumes kernel threads much
 		// than other platforms for some reason.
 		// When we monitor the number of allocated Ms by
@@ -628,7 +628,7 @@ func TestLookupDotsWithLocalSource(t *testing.T) {
 }
 
 func TestLookupDotsWithRemoteSource(t *testing.T) {
-	if runtime.GOOS == "darwin" {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		testenv.SkipFlaky(t, 27992)
 	}
 	mustHaveExternalNetwork(t)
diff --git a/src/net/main_test.go b/src/net/main_test.go
index 85a269d0f4..2d5be2ee5f 100644
--- a/src/net/main_test.go
+++ b/src/net/main_test.go
@@ -133,7 +133,7 @@ func setupTestData() {
 			{"udp6", "[" + addr + "%" + ifi.Name + "]:0", false},
 		}...)
 		switch runtime.GOOS {
-		case "darwin", "dragonfly", "freebsd", "openbsd", "netbsd":
+		case "darwin", "ios", "dragonfly", "freebsd", "openbsd", "netbsd":
 			ipv6LinkLocalUnicastTCPTests = append(ipv6LinkLocalUnicastTCPTests, []ipv6LinkLocalUnicastTest{
 				{"tcp", "[localhost%" + ifi.Name + "]:0", true},
 				{"tcp6", "[localhost%" + ifi.Name + "]:0", true},
diff --git a/src/net/platform_test.go b/src/net/platform_test.go
index d3bb918edb..4b92bb6df0 100644
--- a/src/net/platform_test.go
+++ b/src/net/platform_test.go
@@ -59,7 +59,7 @@ func testableNetwork(network string) bool {
 		}
 	case "unixpacket":
 		switch runtime.GOOS {
-		case "aix", "android", "darwin", "plan9", "windows":
+		case "aix", "android", "darwin", "ios", "plan9", "windows":
 			return false
 		case "netbsd":
 			// It passes on amd64 at least. 386 fails (Issue 22927). arm is unknown.
@@ -82,7 +82,7 @@ func testableNetwork(network string) bool {
 }
 
 func iOS() bool {
-	return runtime.GOOS == "darwin" && runtime.GOARCH == "arm64"
+	return (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64"
 }
 
 // testableAddress reports whether address of network is testable on
diff --git a/src/net/sock_bsd.go b/src/net/sock_bsd.go
index 516e557cfd..73fb6be814 100644
--- a/src/net/sock_bsd.go
+++ b/src/net/sock_bsd.go
@@ -17,7 +17,7 @@ func maxListenerBacklog() int {
 		err error
 	)
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		n, err = syscall.SysctlUint32("kern.ipc.somaxconn")
 	case "freebsd":
 		n, err = syscall.SysctlUint32("kern.ipc.soacceptqueue")
diff --git a/src/net/tcpsock_test.go b/src/net/tcpsock_test.go
index 8a70496693..6e905aa091 100644
--- a/src/net/tcpsock_test.go
+++ b/src/net/tcpsock_test.go
@@ -647,7 +647,7 @@ func TestTCPSelfConnect(t *testing.T) {
 		n = 1000
 	}
 	switch runtime.GOOS {
-	case "darwin", "dragonfly", "freebsd", "netbsd", "openbsd", "plan9", "illumos", "solaris", "windows":
+	case "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd", "plan9", "illumos", "solaris", "windows":
 		// Non-Linux systems take a long time to figure
 		// out that there is nothing listening on localhost.
 		n = 100
diff --git a/src/net/udpsock_test.go b/src/net/udpsock_test.go
index 947381a57b..327eba6541 100644
--- a/src/net/udpsock_test.go
+++ b/src/net/udpsock_test.go
@@ -327,7 +327,7 @@ func TestUDPZeroBytePayload(t *testing.T) {
 	switch runtime.GOOS {
 	case "plan9":
 		t.Skipf("not supported on %s", runtime.GOOS)
-	case "darwin":
+	case "darwin", "ios":
 		testenv.SkipFlaky(t, 29225)
 	}
 
diff --git a/src/net/writev_test.go b/src/net/writev_test.go
index d6dce3cc69..a6b3285e57 100644
--- a/src/net/writev_test.go
+++ b/src/net/writev_test.go
@@ -154,7 +154,7 @@ func testBuffer_writeTo(t *testing.T, chunks int, useCopy bool) {
 
 		var wantSum int
 		switch runtime.GOOS {
-		case "android", "darwin", "dragonfly", "freebsd", "illumos", "linux", "netbsd", "openbsd":
+		case "android", "darwin", "ios", "dragonfly", "freebsd", "illumos", "linux", "netbsd", "openbsd":
 			var wantMinCalls int
 			wantSum = want.Len()
 			v := chunks
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index 5446dd5003..dc7d868a32 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -129,7 +129,7 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
 	// used with kqueue.
 	if kind == kindOpenFile {
 		switch runtime.GOOS {
-		case "darwin", "dragonfly", "freebsd", "netbsd", "openbsd":
+		case "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd":
 			var st syscall.Stat_t
 			err := ignoringEINTR(func() error {
 				return syscall.Fstat(fdi, &st)
@@ -150,7 +150,7 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
 			// on Darwin, kqueue does not work properly with fifos:
 			// closing the last writer does not cause a kqueue event
 			// for any readers. See issue #24164.
-			if runtime.GOOS == "darwin" && typ == syscall.S_IFIFO {
+			if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && typ == syscall.S_IFIFO {
 				pollable = false
 			}
 		}
diff --git a/src/os/os_test.go b/src/os/os_test.go
index 3359301316..2bb57d866f 100644
--- a/src/os/os_test.go
+++ b/src/os/os_test.go
@@ -52,7 +52,7 @@ var sysdir = func() *sysDir {
 				"libpowermanager.so",
 			},
 		}
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			wd, err := syscall.Getwd()
@@ -144,7 +144,7 @@ func localTmp() string {
 	switch runtime.GOOS {
 	case "android", "windows":
 		return TempDir()
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			return TempDir()
@@ -481,7 +481,7 @@ func TestReaddirnamesOneAtATime(t *testing.T) {
 	switch runtime.GOOS {
 	case "android":
 		dir = "/system/bin"
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			wd, err := Getwd()
@@ -1304,7 +1304,7 @@ func TestChdirAndGetwd(t *testing.T) {
 		dirs = []string{"/system/bin"}
 	case "plan9":
 		dirs = []string{"/", "/usr"}
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			dirs = nil
diff --git a/src/os/path_test.go b/src/os/path_test.go
index d586daf936..3fe9c5ffa3 100644
--- a/src/os/path_test.go
+++ b/src/os/path_test.go
@@ -107,7 +107,7 @@ func TestMkdirAllAtSlash(t *testing.T) {
 	switch runtime.GOOS {
 	case "android", "plan9", "windows":
 		t.Skipf("skipping on %s", runtime.GOOS)
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			t.Skipf("skipping on darwin/arm64, mkdir returns EPERM")
diff --git a/src/os/removeall_test.go b/src/os/removeall_test.go
index 8a71f687ed..1e5c650fe1 100644
--- a/src/os/removeall_test.go
+++ b/src/os/removeall_test.go
@@ -158,7 +158,7 @@ func TestRemoveAllLarge(t *testing.T) {
 
 func TestRemoveAllLongPath(t *testing.T) {
 	switch runtime.GOOS {
-	case "aix", "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "illumos", "solaris":
+	case "aix", "darwin", "ios", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "illumos", "solaris":
 		break
 	default:
 		t.Skip("skipping for not implemented platforms")
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index d6f680556c..ca100ff071 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -431,7 +431,7 @@ func chtmpdir(t *testing.T) (restore func()) {
 }
 
 func TestWalk(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		restore := chtmpdir(t)
 		defer restore()
 	}
@@ -1278,7 +1278,7 @@ func TestDriveLetterInEvalSymlinks(t *testing.T) {
 }
 
 func TestBug3486(t *testing.T) { // https://golang.org/issue/3486
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skipf("skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 	root, err := filepath.EvalSymlinks(runtime.GOROOT() + "/test")
diff --git a/src/runtime/debug/panic_test.go b/src/runtime/debug/panic_test.go
index 4b7830e100..93be216985 100644
--- a/src/runtime/debug/panic_test.go
+++ b/src/runtime/debug/panic_test.go
@@ -20,7 +20,7 @@ func TestPanicOnFault(t *testing.T) {
 	if runtime.GOARCH == "s390x" {
 		t.Skip("s390x fault addresses are missing the low order bits")
 	}
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skip("darwin/arm64 doesn't provide fault addresses")
 	}
 	m, err := syscall.Mmap(-1, 0, 0x1000, syscall.PROT_READ /* Note: no PROT_WRITE */, syscall.MAP_SHARED|syscall.MAP_ANON)
diff --git a/src/runtime/internal/sys/gengoos.go b/src/runtime/internal/sys/gengoos.go
index 952b13649d..2a4bf0c3b4 100644
--- a/src/runtime/internal/sys/gengoos.go
+++ b/src/runtime/internal/sys/gengoos.go
@@ -44,6 +44,9 @@ func main() {
 	}
 
 	for _, target := range gooses {
+		if target == "nacl" {
+			continue
+		}
 		var buf bytes.Buffer
 		fmt.Fprintf(&buf, "// Code generated by gengoos.go using 'go generate'. DO NOT EDIT.\n\n")
 		if target == "linux" {
@@ -52,6 +55,9 @@ func main() {
 		if target == "solaris" {
 			fmt.Fprintf(&buf, "// +build !illumos\n") // must explicitly exclude illumos for solaris
 		}
+		if target == "darwin" {
+			fmt.Fprintf(&buf, "// +build !ios\n") // must explicitly exclude ios for darwin
+		}
 		fmt.Fprintf(&buf, "// +build %s\n\n", target) // must explicitly include target for bootstrapping purposes
 		fmt.Fprintf(&buf, "package sys\n\n")
 		fmt.Fprintf(&buf, "const GOOS = `%s`\n\n", target)
@@ -69,6 +75,9 @@ func main() {
 	}
 
 	for _, target := range goarches {
+		if target == "amd64p32" {
+			continue
+		}
 		var buf bytes.Buffer
 		fmt.Fprintf(&buf, "// Code generated by gengoos.go using 'go generate'. DO NOT EDIT.\n\n")
 		fmt.Fprintf(&buf, "// +build %s\n\n", target) // must explicitly include target for bootstrapping purposes
diff --git a/src/runtime/internal/sys/zgoos_aix.go b/src/runtime/internal/sys/zgoos_aix.go
index d97485c43c..0631d02aa5 100644
--- a/src/runtime/internal/sys/zgoos_aix.go
+++ b/src/runtime/internal/sys/zgoos_aix.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_android.go b/src/runtime/internal/sys/zgoos_android.go
index eec970b064..d356a40bec 100644
--- a/src/runtime/internal/sys/zgoos_android.go
+++ b/src/runtime/internal/sys/zgoos_android.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_darwin.go b/src/runtime/internal/sys/zgoos_darwin.go
index c40819ee55..6aa2db7e3a 100644
--- a/src/runtime/internal/sys/zgoos_darwin.go
+++ b/src/runtime/internal/sys/zgoos_darwin.go
@@ -1,5 +1,6 @@
 // Code generated by gengoos.go using 'go generate'. DO NOT EDIT.
 
+// +build !ios
 // +build darwin
 
 package sys
@@ -13,6 +14,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_dragonfly.go b/src/runtime/internal/sys/zgoos_dragonfly.go
index 3dc4edcc31..88ee1174f1 100644
--- a/src/runtime/internal/sys/zgoos_dragonfly.go
+++ b/src/runtime/internal/sys/zgoos_dragonfly.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 1
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_freebsd.go b/src/runtime/internal/sys/zgoos_freebsd.go
index 6c98b342f9..8de2ec0559 100644
--- a/src/runtime/internal/sys/zgoos_freebsd.go
+++ b/src/runtime/internal/sys/zgoos_freebsd.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 1
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_hurd.go b/src/runtime/internal/sys/zgoos_hurd.go
index d6dcc7bad4..183ccb02a1 100644
--- a/src/runtime/internal/sys/zgoos_hurd.go
+++ b/src/runtime/internal/sys/zgoos_hurd.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 1
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_illumos.go b/src/runtime/internal/sys/zgoos_illumos.go
index 17f4ecc34e..d04134e1df 100644
--- a/src/runtime/internal/sys/zgoos_illumos.go
+++ b/src/runtime/internal/sys/zgoos_illumos.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 1
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_ios.go b/src/runtime/internal/sys/zgoos_ios.go
new file mode 100644
index 0000000000..cf6e9d61f0
--- /dev/null
+++ b/src/runtime/internal/sys/zgoos_ios.go
@@ -0,0 +1,25 @@
+// Code generated by gengoos.go using 'go generate'. DO NOT EDIT.
+
+// +build ios
+
+package sys
+
+const GOOS = `ios`
+
+const GoosAix = 0
+const GoosAndroid = 0
+const GoosDarwin = 0
+const GoosDragonfly = 0
+const GoosFreebsd = 0
+const GoosHurd = 0
+const GoosIllumos = 0
+const GoosIos = 1
+const GoosJs = 0
+const GoosLinux = 0
+const GoosNacl = 0
+const GoosNetbsd = 0
+const GoosOpenbsd = 0
+const GoosPlan9 = 0
+const GoosSolaris = 0
+const GoosWindows = 0
+const GoosZos = 0
diff --git a/src/runtime/internal/sys/zgoos_js.go b/src/runtime/internal/sys/zgoos_js.go
index 74c9943d9b..1d9279ab38 100644
--- a/src/runtime/internal/sys/zgoos_js.go
+++ b/src/runtime/internal/sys/zgoos_js.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 1
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_linux.go b/src/runtime/internal/sys/zgoos_linux.go
index 1d5fcb0685..0f718d704f 100644
--- a/src/runtime/internal/sys/zgoos_linux.go
+++ b/src/runtime/internal/sys/zgoos_linux.go
@@ -14,6 +14,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 1
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_netbsd.go b/src/runtime/internal/sys/zgoos_netbsd.go
index 194fa6e432..2ae149ff13 100644
--- a/src/runtime/internal/sys/zgoos_netbsd.go
+++ b/src/runtime/internal/sys/zgoos_netbsd.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_openbsd.go b/src/runtime/internal/sys/zgoos_openbsd.go
index 2108691679..7d4d61e4ca 100644
--- a/src/runtime/internal/sys/zgoos_openbsd.go
+++ b/src/runtime/internal/sys/zgoos_openbsd.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_plan9.go b/src/runtime/internal/sys/zgoos_plan9.go
index e632a90b2e..30aec46df3 100644
--- a/src/runtime/internal/sys/zgoos_plan9.go
+++ b/src/runtime/internal/sys/zgoos_plan9.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_solaris.go b/src/runtime/internal/sys/zgoos_solaris.go
index 67b2ffbfcd..4bb8c99bce 100644
--- a/src/runtime/internal/sys/zgoos_solaris.go
+++ b/src/runtime/internal/sys/zgoos_solaris.go
@@ -14,6 +14,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_windows.go b/src/runtime/internal/sys/zgoos_windows.go
index cf2d6f4fb0..d1f4290204 100644
--- a/src/runtime/internal/sys/zgoos_windows.go
+++ b/src/runtime/internal/sys/zgoos_windows.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/internal/sys/zgoos_zos.go b/src/runtime/internal/sys/zgoos_zos.go
index e5d79accb4..d22be46fc0 100644
--- a/src/runtime/internal/sys/zgoos_zos.go
+++ b/src/runtime/internal/sys/zgoos_zos.go
@@ -13,6 +13,7 @@ const GoosDragonfly = 0
 const GoosFreebsd = 0
 const GoosHurd = 0
 const GoosIllumos = 0
+const GoosIos = 0
 const GoosJs = 0
 const GoosLinux = 0
 const GoosNacl = 0
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index e46327f9ce..4fa14996c2 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -207,7 +207,7 @@ const (
 	// arenaBaseOffset to offset into the top 4 GiB.
 	//
 	// WebAssembly currently has a limit of 4GB linear memory.
-	heapAddrBits = (_64bit*(1-sys.GoarchWasm)*(1-sys.GoosDarwin*sys.GoarchArm64))*48 + (1-_64bit+sys.GoarchWasm)*(32-(sys.GoarchMips+sys.GoarchMipsle)) + 33*sys.GoosDarwin*sys.GoarchArm64
+	heapAddrBits = (_64bit*(1-sys.GoarchWasm)*(1-(sys.GoosDarwin+sys.GoosIos)*sys.GoarchArm64))*48 + (1-_64bit+sys.GoarchWasm)*(32-(sys.GoarchMips+sys.GoarchMipsle)) + 33*(sys.GoosDarwin+sys.GoosIos)*sys.GoarchArm64
 
 	// maxAlloc is the maximum size of an allocation. On 64-bit,
 	// it's theoretically possible to allocate 1<<heapAddrBits bytes. On
@@ -521,7 +521,7 @@ func mallocinit() {
 		for i := 0x7f; i >= 0; i-- {
 			var p uintptr
 			switch {
-			case GOARCH == "arm64" && GOOS == "darwin":
+			case GOARCH == "arm64" && (GOOS == "darwin" || GOOS == "ios"):
 				p = uintptr(i)<<40 | uintptrMask&(0x0013<<28)
 			case GOARCH == "arm64":
 				p = uintptr(i)<<40 | uintptrMask&(0x0040<<32)
diff --git a/src/runtime/mgcscavenge.go b/src/runtime/mgcscavenge.go
index b74da1057a..9d6f551768 100644
--- a/src/runtime/mgcscavenge.go
+++ b/src/runtime/mgcscavenge.go
@@ -90,7 +90,7 @@ const (
 	//
 	// This ratio is used as part of multiplicative factor to help the scavenger account
 	// for the additional costs of using scavenged memory in its pacing.
-	scavengeCostRatio = 0.7 * sys.GoosDarwin
+	scavengeCostRatio = 0.7 * (sys.GoosDarwin + sys.GoosIos)
 
 	// scavengeReservationShards determines the amount of memory the scavenger
 	// should reserve for scavenging at a time. Specifically, the amount of
diff --git a/src/runtime/mkpreempt.go b/src/runtime/mkpreempt.go
index 44dea22ef3..c2e14cdcd6 100644
--- a/src/runtime/mkpreempt.go
+++ b/src/runtime/mkpreempt.go
@@ -361,6 +361,9 @@ func genARM64() {
 	p("#ifdef GOOS_darwin")
 	p("MOVD R30, (RSP)")
 	p("#endif")
+	p("#ifdef GOOS_ios")
+	p("MOVD R30, (RSP)")
+	p("#endif")
 
 	l.save()
 	p("CALL ·asyncPreempt2(SB)")
diff --git a/src/runtime/pprof/pprof_rusage.go b/src/runtime/pprof/pprof_rusage.go
index d42e6ed473..7954673811 100644
--- a/src/runtime/pprof/pprof_rusage.go
+++ b/src/runtime/pprof/pprof_rusage.go
@@ -19,7 +19,7 @@ func addMaxRSS(w io.Writer) {
 	switch runtime.GOOS {
 	case "linux", "android":
 		rssToBytes = 1024
-	case "darwin":
+	case "darwin", "ios":
 		rssToBytes = 1
 	default:
 		panic("unsupported OS")
diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 7149bfb31f..43307aeab9 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -262,7 +262,7 @@ func parseProfile(t *testing.T, valBytes []byte, f func(uintptr, []*profile.Loca
 // as interpreted by matches, and returns the parsed profile.
 func testCPUProfile(t *testing.T, matches matchFunc, need []string, avoid []string, f func(dur time.Duration)) *profile.Profile {
 	switch runtime.GOOS {
-	case "darwin":
+	case "darwin", "ios":
 		switch runtime.GOARCH {
 		case "arm64":
 			// nothing
@@ -280,7 +280,7 @@ func testCPUProfile(t *testing.T, matches matchFunc, need []string, avoid []stri
 
 	broken := false
 	switch runtime.GOOS {
-	case "darwin", "dragonfly", "netbsd", "illumos", "solaris":
+	case "darwin", "ios", "dragonfly", "netbsd", "illumos", "solaris":
 		broken = true
 	case "openbsd":
 		if runtime.GOARCH == "arm" || runtime.GOARCH == "arm64" {
diff --git a/src/runtime/preempt_arm64.s b/src/runtime/preempt_arm64.s
index 3c27b52de1..d0e77659c3 100644
--- a/src/runtime/preempt_arm64.s
+++ b/src/runtime/preempt_arm64.s
@@ -13,6 +13,9 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	#ifdef GOOS_darwin
 	MOVD R30, (RSP)
 	#endif
+	#ifdef GOOS_ios
+	MOVD R30, (RSP)
+	#endif
 	MOVD R0, 8(RSP)
 	MOVD R1, 16(RSP)
 	MOVD R2, 24(RSP)
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 5b6a30d40b..a1e2ed0680 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -503,7 +503,7 @@ func cpuinit() {
 	var env string
 
 	switch GOOS {
-	case "aix", "darwin", "dragonfly", "freebsd", "netbsd", "openbsd", "illumos", "solaris", "linux":
+	case "aix", "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd", "illumos", "solaris", "linux":
 		cpu.DebugOptions = true
 
 		// Similar to goenv_unix but extracts the environment value for
@@ -1158,7 +1158,7 @@ func mstart() {
 
 	// Exit this thread.
 	switch GOOS {
-	case "windows", "solaris", "illumos", "plan9", "darwin", "aix":
+	case "windows", "solaris", "illumos", "plan9", "darwin", "ios", "aix":
 		// Windows, Solaris, illumos, Darwin, AIX and Plan 9 always system-allocate
 		// the stack, but put it in _g_.stack before mstart,
 		// so the logic above hasn't set osStack yet.
@@ -1487,7 +1487,7 @@ func allocm(_p_ *p, fn func(), id int64) *m {
 
 	// In case of cgo or Solaris or illumos or Darwin, pthread_create will make us a stack.
 	// Windows and Plan 9 will layout sched stack on OS stack.
-	if iscgo || GOOS == "solaris" || GOOS == "illumos" || GOOS == "windows" || GOOS == "plan9" || GOOS == "darwin" {
+	if iscgo || GOOS == "solaris" || GOOS == "illumos" || GOOS == "windows" || GOOS == "plan9" || GOOS == "darwin" || GOOS == "ios" {
 		mp.g0 = malg(-1)
 	} else {
 		mp.g0 = malg(8192 * sys.StackGuardMultiplier)
@@ -4077,7 +4077,7 @@ func sigprof(pc, sp, lr uintptr, gp *g, mp *m) {
 		// Normal traceback is impossible or has failed.
 		// See if it falls into several common cases.
 		n = 0
-		if (GOOS == "windows" || GOOS == "solaris" || GOOS == "illumos" || GOOS == "darwin" || GOOS == "aix") && mp.libcallg != 0 && mp.libcallpc != 0 && mp.libcallsp != 0 {
+		if (GOOS == "windows" || GOOS == "solaris" || GOOS == "illumos" || GOOS == "darwin" || GOOS == "ios" || GOOS == "aix") && mp.libcallg != 0 && mp.libcallpc != 0 && mp.libcallsp != 0 {
 			// Libcall, i.e. runtime syscall on windows.
 			// Collect Go stack that leads to the call.
 			n = gentraceback(mp.libcallpc, mp.libcallsp, 0, mp.libcallg.ptr(), 0, &stk[0], len(stk), nil, nil, 0)
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 9652b6a5a4..48e07f789b 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -1060,4 +1060,4 @@ var (
 )
 
 // Must agree with cmd/internal/objabi.Framepointer_enabled.
-const framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" && (GOOS == "linux" || GOOS == "darwin")
+const framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" && (GOOS == "linux" || GOOS == "darwin" || GOOS == "ios")
diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index bbfc18e37b..a3d6f34c88 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -346,7 +346,7 @@ const preemptMSupported = true
 // safe-point, it will preempt the goroutine. It always atomically
 // increments mp.preemptGen after handling a preemption request.
 func preemptM(mp *m) {
-	if GOOS == "darwin" && GOARCH == "arm64" && !iscgo {
+	if (GOOS == "darwin" || GOOS == "ios") && GOARCH == "arm64" && !iscgo {
 		// On darwin, we use libc calls, and cgo is required on ARM64
 		// so we have TLS set up to save/restore G during C calls. If cgo is
 		// absent, we cannot save/restore G in TLS, and if a signal is
@@ -975,7 +975,7 @@ func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
 	// This function and its caller sigtrampgo assumes SIGPIPE is delivered on the
 	// originating thread. This property does not hold on macOS (golang.org/issue/33384),
 	// so we have no choice but to ignore SIGPIPE.
-	if GOOS == "darwin" && sig == _SIGPIPE {
+	if (GOOS == "darwin" || GOOS == "ios") && sig == _SIGPIPE {
 		return true
 	}
 
diff --git a/src/runtime/sigqueue.go b/src/runtime/sigqueue.go
index 3bf07cb5a6..0605f5da80 100644
--- a/src/runtime/sigqueue.go
+++ b/src/runtime/sigqueue.go
@@ -105,7 +105,7 @@ Send:
 			break Send
 		case sigReceiving:
 			if atomic.Cas(&sig.state, sigReceiving, sigIdle) {
-				if GOOS == "darwin" {
+				if GOOS == "darwin" || GOOS == "ios" {
 					sigNoteWakeup(&sig.note)
 					break Send
 				}
@@ -140,7 +140,7 @@ func signal_recv() uint32 {
 				throw("signal_recv: inconsistent state")
 			case sigIdle:
 				if atomic.Cas(&sig.state, sigIdle, sigReceiving) {
-					if GOOS == "darwin" {
+					if GOOS == "darwin" || GOOS == "ios" {
 						sigNoteSleep(&sig.note)
 						break Receive
 					}
@@ -194,7 +194,7 @@ func signal_enable(s uint32) {
 	if !sig.inuse {
 		// This is the first call to signal_enable. Initialize.
 		sig.inuse = true // enable reception of signals; cannot disable
-		if GOOS == "darwin" {
+		if GOOS == "darwin" || GOOS == "ios" {
 			sigNoteSetup(&sig.note)
 		} else {
 			noteclear(&sig.note)
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index adcef071da..3802cd049e 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -66,7 +66,7 @@ const (
 	// to each stack below the usual guard area for OS-specific
 	// purposes like signal handling. Used on Windows, Plan 9,
 	// and iOS because they do not use a separate stack.
-	_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + sys.GoosDarwin*sys.GoarchArm64*1024
+	_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + (sys.GoosDarwin+sys.GoosIos)*sys.GoarchArm64*1024
 
 	// The minimum size of stack used by Go code
 	_StackMin = 2048
diff --git a/src/runtime/tls_arm64.h b/src/runtime/tls_arm64.h
index f60f4f6d5b..0804fa3502 100644
--- a/src/runtime/tls_arm64.h
+++ b/src/runtime/tls_arm64.h
@@ -15,6 +15,12 @@
 #endif
 
 #ifdef GOOS_darwin
+#define TLS_darwin
+#endif
+#ifdef GOOS_ios
+#define TLS_darwin
+#endif
+#ifdef TLS_darwin
 #define TPIDR TPIDRRO_EL0
 #define TLSG_IS_VARIABLE
 #define MRS_TPIDR_R0 WORD $0xd53bd060 // MRS TPIDRRO_EL0, R0
diff --git a/src/runtime/tls_arm64.s b/src/runtime/tls_arm64.s
index 999914d655..7846fac6c5 100644
--- a/src/runtime/tls_arm64.s
+++ b/src/runtime/tls_arm64.s
@@ -13,7 +13,7 @@ TEXT runtime·load_g(SB),NOSPLIT,$0
 	CBZ	R0, nocgo
 
 	MRS_TPIDR_R0
-#ifdef GOOS_darwin
+#ifdef TLS_darwin
 	// Darwin sometimes returns unaligned pointers
 	AND	$0xfffffffffffffff8, R0
 #endif
@@ -29,7 +29,7 @@ TEXT runtime·save_g(SB),NOSPLIT,$0
 	CBZ	R0, nocgo
 
 	MRS_TPIDR_R0
-#ifdef GOOS_darwin
+#ifdef TLS_darwin
 	// Darwin sometimes returns unaligned pointers
 	AND	$0xfffffffffffffff8, R0
 #endif
diff --git a/src/syscall/exec_unix.go b/src/syscall/exec_unix.go
index cb08b7084c..725c2bc1f9 100644
--- a/src/syscall/exec_unix.go
+++ b/src/syscall/exec_unix.go
@@ -296,7 +296,7 @@ func Exec(argv0 string, argv []string, envv []string) (err error) {
 			uintptr(unsafe.Pointer(argv0p)),
 			uintptr(unsafe.Pointer(&argvp[0])),
 			uintptr(unsafe.Pointer(&envvp[0])))
-	} else if runtime.GOOS == "darwin" {
+	} else if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		// Similarly on Darwin.
 		err1 = execveDarwin(argv0p, &argvp[0], &envvp[0])
 	} else {
diff --git a/src/syscall/sockcmsg_unix_other.go b/src/syscall/sockcmsg_unix_other.go
index fbafbf8341..3aaf7c3616 100644
--- a/src/syscall/sockcmsg_unix_other.go
+++ b/src/syscall/sockcmsg_unix_other.go
@@ -20,7 +20,7 @@ func cmsgAlignOf(salen int) int {
 	case "aix":
 		// There is no alignment on AIX.
 		salign = 1
-	case "darwin", "illumos", "solaris":
+	case "darwin", "ios", "illumos", "solaris":
 		// NOTE: It seems like 64-bit Darwin, Illumos and Solaris
 		// kernels still require 32-bit aligned access to network
 		// subsystem.
diff --git a/src/syscall/syscall_bsd.go b/src/syscall/syscall_bsd.go
index fda9d613d3..b52de7450f 100644
--- a/src/syscall/syscall_bsd.go
+++ b/src/syscall/syscall_bsd.go
@@ -277,7 +277,7 @@ func Accept(fd int) (nfd int, sa Sockaddr, err error) {
 	if err != nil {
 		return
 	}
-	if runtime.GOOS == "darwin" && len == 0 {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && len == 0 {
 		// Accepted socket has no address.
 		// This is likely due to a bug in xnu kernels,
 		// where instead of ECONNABORTED error socket
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index 56abce19cd..91c939e0ea 100644
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -22,7 +22,7 @@ var (
 )
 
 const (
-	darwin64Bit = runtime.GOOS == "darwin" && sizeofPtr == 8
+	darwin64Bit = (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && sizeofPtr == 8
 	netbsd32Bit = runtime.GOOS == "netbsd" && sizeofPtr == 4
 )
 
diff --git a/src/syscall/syscall_unix_test.go b/src/syscall/syscall_unix_test.go
index 3c7982eefe..7e9bb0c3ac 100644
--- a/src/syscall/syscall_unix_test.go
+++ b/src/syscall/syscall_unix_test.go
@@ -70,7 +70,7 @@ func _() {
 // Thus this test also verifies that the Flock_t structure can be
 // roundtripped with F_SETLK and F_GETLK.
 func TestFcntlFlock(t *testing.T) {
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		t.Skip("skipping; no child processes allowed on iOS")
 	}
 	flock := syscall.Flock_t{
@@ -336,7 +336,7 @@ func TestRlimit(t *testing.T) {
 	}
 	set := rlimit
 	set.Cur = set.Max - 1
-	if runtime.GOOS == "darwin" && set.Cur > 4096 {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && set.Cur > 4096 {
 		// rlim_min for RLIMIT_NOFILE should be equal to
 		// or lower than kern.maxfilesperproc, which on
 		// some machines are 4096. See #40564.
@@ -353,7 +353,7 @@ func TestRlimit(t *testing.T) {
 	}
 	set = rlimit
 	set.Cur = set.Max - 1
-	if runtime.GOOS == "darwin" && set.Cur > 4096 {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && set.Cur > 4096 {
 		set.Cur = 4096
 	}
 	if set != get {
diff --git a/src/time/tick_test.go b/src/time/tick_test.go
index c0c6e76b53..9a1cdf9ab2 100644
--- a/src/time/tick_test.go
+++ b/src/time/tick_test.go
@@ -21,7 +21,7 @@ func TestTicker(t *testing.T) {
 	delta := 20 * Millisecond
 
 	// On Darwin ARM64 the tick frequency seems limited. Issue 35692.
-	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
 		// The following test will run ticker count/2 times then reset
 		// the ticker to double the duration for the rest of count/2.
 		// Since tick frequency is limited on Darwin ARM64, use even
diff --git a/src/time/zoneinfo_ios.go b/src/time/zoneinfo_darwin_arm64.go
index 6016a7925a..65feb84711 100644
--- a/src/time/zoneinfo_ios.go
+++ b/src/time/zoneinfo_darwin_arm64.go
@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin
-// +build arm64
-
 package time
 
 import (