internal/byteorder: new package

Currently in a lot of packages we define functions for appending/decoding
mostly BigEndian data (see internal/chacha8rand, net/netip,
internal/boring/sha, hash/crc64, and probably more), because we don't
want to depend on encoding/binary, because of #54097.

This change introduces a new package internal/byteorder, that
will allow us to remove all of the functions and replace them with
internal/byteorder.

Updates #54097

Change-Id: I03e5ea1eb721dd98bdabdb25786f889cc5de54c5
GitHub-Last-Rev: 3f07d3dfb4
GitHub-Pull-Request: golang/go#67183
Reviewed-on: https://go-review.googlesource.com/c/go/+/583298
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Commit-Queue: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/inline/inl.go

@@ -545,6 +545,28 @@ opSwitch:
 				}
 			}
 		}
+
+		if n.Fun.Op() == ir.ONAME {
+			name := n.Fun.(*ir.Name)
+			if name.Class == ir.PFUNC {
+				// Special case: on architectures that can do unaligned loads,
+				// explicitly mark internal/byteorder methods as cheap,
+				// because in practice they are, even though our inlining
+				// budgeting system does not see that. See issue 42958.
+				if base.Ctxt.Arch.CanMergeLoads && name.Sym().Pkg.Path == "internal/byteorder" {
+					switch name.Sym().Name {
+					case "LeUint64", "LeUint32", "LeUint16",
+						"BeUint64", "BeUint32", "BeUint16",
+						"LePutUint64", "LePutUint32", "LePutUint16",
+						"BePutUint64", "BePutUint32", "BePutUint16",
+						"LeAppendUint64", "LeAppendUint32", "LeAppendUint16",
+						"BeAppendUint64", "BeAppendUint32", "BeAppendUint16":
+						cheap = true
+					}
+				}
+			}
+		}
+
 		if cheap {
 			break // treat like any other node, that is, cost of 1
 		}

src/go/build/deps_test.go

@@ -67,6 +67,7 @@ var depsRules = `
 	internal/goos
 	< internal/bytealg
 	< internal/stringslite
+	< internal/byteorder
 	< internal/itoa
 	< internal/unsafeheader
 	< runtime/internal/sys

src/internal/byteorder/byteorder.go

@@ -0,0 +1,149 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package byteorder provides functions for decoding and encoding
+// little and big endian integer types from/to byte slices.
+package byteorder
+
+func LeUint16(b []byte) uint16 {
+	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint16(b[0]) | uint16(b[1])<<8
+}
+
+func LePutUint16(b []byte, v uint16) {
+	_ = b[1] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+}
+
+func LeAppendUint16(b []byte, v uint16) []byte {
+	return append(b,
+		byte(v),
+		byte(v>>8),
+	)
+}
+
+func LeUint32(b []byte) uint32 {
+	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+}
+
+func LePutUint32(b []byte, v uint32) {
+	_ = b[3] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+}
+
+func LeAppendUint32(b []byte, v uint32) []byte {
+	return append(b,
+		byte(v),
+		byte(v>>8),
+		byte(v>>16),
+		byte(v>>24),
+	)
+}
+
+func LeUint64(b []byte) uint64 {
+	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
+		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
+}
+
+func LePutUint64(b []byte, v uint64) {
+	_ = b[7] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+	b[4] = byte(v >> 32)
+	b[5] = byte(v >> 40)
+	b[6] = byte(v >> 48)
+	b[7] = byte(v >> 56)
+}
+
+func LeAppendUint64(b []byte, v uint64) []byte {
+	return append(b,
+		byte(v),
+		byte(v>>8),
+		byte(v>>16),
+		byte(v>>24),
+		byte(v>>32),
+		byte(v>>40),
+		byte(v>>48),
+		byte(v>>56),
+	)
+}
+
+func BeUint16(b []byte) uint16 {
+	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint16(b[1]) | uint16(b[0])<<8
+}
+
+func BePutUint16(b []byte, v uint16) {
+	_ = b[1] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 8)
+	b[1] = byte(v)
+}
+
+func BeAppendUint16(b []byte, v uint16) []byte {
+	return append(b,
+		byte(v>>8),
+		byte(v),
+	)
+}
+
+func BeUint32(b []byte) uint32 {
+	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
+}
+
+func BePutUint32(b []byte, v uint32) {
+	_ = b[3] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 24)
+	b[1] = byte(v >> 16)
+	b[2] = byte(v >> 8)
+	b[3] = byte(v)
+}
+
+func BeAppendUint32(b []byte, v uint32) []byte {
+	return append(b,
+		byte(v>>24),
+		byte(v>>16),
+		byte(v>>8),
+		byte(v),
+	)
+}
+
+func BeUint64(b []byte) uint64 {
+	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
+		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
+}
+
+func BePutUint64(b []byte, v uint64) {
+	_ = b[7] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 56)
+	b[1] = byte(v >> 48)
+	b[2] = byte(v >> 40)
+	b[3] = byte(v >> 32)
+	b[4] = byte(v >> 24)
+	b[5] = byte(v >> 16)
+	b[6] = byte(v >> 8)
+	b[7] = byte(v)
+}
+
+func BeAppendUint64(b []byte, v uint64) []byte {
+	return append(b,
+		byte(v>>56),
+		byte(v>>48),
+		byte(v>>40),
+		byte(v>>32),
+		byte(v>>24),
+		byte(v>>16),
+		byte(v>>8),
+		byte(v),
+	)
+}