src/cmd/compile/internal/amd64/versions_test.go - go - Git at Google

 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package amd64_test

 import (
 	"bufio"
 	"debug/elf"
 	"debug/macho"
 	"fmt"
 	"internal/testenv"
 	"io"
 	"math"
 	"math/bits"
 	"os"
 	"os/exec"
 	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
 	"testing"
 )

 // Test to make sure that when building for GOAMD64=v1, we don't
 // use any >v1 instructions.
 func TestGoAMD64v1(t *testing.T) {
 	if runtime.GOARCH != "amd64" {
 		t.Skip("amd64-only test")
 	}
 	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
 		t.Skip("test only works on elf or macho platforms")
 	}
 	if v := os.Getenv("GOAMD64"); v != "" && v != "v1" {
 		// Test runs only on v1 (which is the default).
 		// TODO: use build tags from #45454 instead.
 		t.Skip("GOAMD64 already set")
 	}
 	if os.Getenv("TESTGOAMD64V1") != "" {
 		t.Skip("recursive call")
 	}

 	// Make a binary which will be a modified version of the
 	// currently running binary.
 	dst, err := os.CreateTemp("", "TestGoAMD64v1")
 	if err != nil {
 		t.Fatalf("failed to create temp file: %v", err)
 	}
 	defer os.Remove(dst.Name())
 	dst.Chmod(0500) // make executable

 	// Clobber all the non-v1 opcodes.
 	opcodes := map[string]bool{}
 	var features []string
 	for feature, opcodeList := range featureToOpcodes {
 		if runtimeFeatures[feature] {
 			features = append(features, fmt.Sprintf("cpu.%s=off", feature))
 		}
 		for _, op := range opcodeList {
 			opcodes[op] = true
 		}
 	}
 	clobber(t, os.Args[0], dst, opcodes)
 	if err = dst.Close(); err != nil {
 		t.Fatalf("can't close binary: %v", err)
 	}

 	// Run the resulting binary.
 	cmd := exec.Command(dst.Name())
 	testenv.CleanCmdEnv(cmd)
 	cmd.Env = append(cmd.Env, "TESTGOAMD64V1=yes")
 	cmd.Env = append(cmd.Env, fmt.Sprintf("GODEBUG=%s", strings.Join(features, ",")))
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		t.Fatalf("couldn't execute test: %s", err)
 	}
 	if string(out) != "PASS\n" {
 		t.Fatalf("test reported error: %s", string(out))
 	}
 }

 // Clobber copies the binary src to dst, replacing all the instructions in opcodes with
 // faulting instructions.
 func clobber(t *testing.T, src string, dst *os.File, opcodes map[string]bool) {
 	// Run objdump to get disassembly.
 	var re *regexp.Regexp
 	var disasm io.Reader
 	if false {
 		// TODO: go tool objdump doesn't disassemble the bmi1 instructions
 		// in question correctly. See issue 48584.
 		cmd := exec.Command("go", "tool", "objdump", src)
 		var err error
 		disasm, err = cmd.StdoutPipe()
 		if err != nil {
 			t.Fatal(err)
 		}
 		if err := cmd.Start(); err != nil {
 			t.Fatal(err)
 		}
 		re = regexp.MustCompile(`^[^:]*:[-0-9]+\s+0x([0-9a-f]+)\s+([0-9a-f]+)\s+([A-Z]+)`)
 	} else {
 		// TODO: we're depending on platform-native objdump here. Hence the Skipf
 		// below if it doesn't run for some reason.
 		cmd := exec.Command("objdump", "-d", src)
 		var err error
 		disasm, err = cmd.StdoutPipe()
 		if err != nil {
 			t.Skipf("can't run test due to missing objdump: %s", err)
 		}
 		if err := cmd.Start(); err != nil {
 			t.Fatal(err)
 		}
 		re = regexp.MustCompile(`^\s*([0-9a-f]+):\s*((?:[0-9a-f][0-9a-f] )+)\s*([a-z0-9]+)`)
 	}

 	// Find all the instruction addresses we need to edit.
 	virtualEdits := map[uint64]bool{}
 	scanner := bufio.NewScanner(disasm)
 	for scanner.Scan() {
 		line := scanner.Text()
 		parts := re.FindStringSubmatch(line)
 		if len(parts) == 0 {
 			continue
 		}
 		addr, err := strconv.ParseUint(parts[1], 16, 64)
 		if err != nil {
 			continue // not a hex address
 		}
 		opcode := strings.ToLower(parts[3])
 		if !opcodes[opcode] {
 			continue
 		}
 		t.Logf("clobbering instruction %s", line)
 		n := (len(parts[2]) - strings.Count(parts[2], " ")) / 2 // number of bytes in instruction encoding
 		for i := 0; i < n; i++ {
 			// Only really need to make the first byte faulting, but might
 			// as well make all the bytes faulting.
 			virtualEdits[addr+uint64(i)] = true
 		}
 	}

 	// Figure out where in the binary the edits must be done.
 	physicalEdits := map[uint64]bool{}
 	if e, err := elf.Open(src); err == nil {
 		for _, sec := range e.Sections {
 			vaddr := sec.Addr
 			paddr := sec.Offset
 			size := sec.Size
 			for a := range virtualEdits {
 				if a >= vaddr && a < vaddr+size {
 					physicalEdits[paddr+(a-vaddr)] = true
 				}
 			}
 		}
 	} else if m, err2 := macho.Open(src); err2 == nil {
 		for _, sec := range m.Sections {
 			vaddr := sec.Addr
 			paddr := uint64(sec.Offset)
 			size := sec.Size
 			for a := range virtualEdits {
 				if a >= vaddr && a < vaddr+size {
 					physicalEdits[paddr+(a-vaddr)] = true
 				}
 			}
 		}
 	} else {
 		t.Log(err)
 		t.Log(err2)
 		t.Fatal("executable format not elf or macho")
 	}
 	if len(virtualEdits) != len(physicalEdits) {
 		t.Fatal("couldn't find an instruction in text sections")
 	}

 	// Copy source to destination, making edits along the way.
 	f, err := os.Open(src)
 	if err != nil {
 		t.Fatal(err)
 	}
 	r := bufio.NewReader(f)
 	w := bufio.NewWriter(dst)
 	a := uint64(0)
 	done := 0
 	for {
 		b, err := r.ReadByte()
 		if err == io.EOF {
 			break
 		}
 		if err != nil {
 			t.Fatal("can't read")
 		}
 		if physicalEdits[a] {
 			b = 0xcc // INT3 opcode
 			done++
 		}
 		err = w.WriteByte(b)
 		if err != nil {
 			t.Fatal("can't write")
 		}
 		a++
 	}
 	if done != len(physicalEdits) {
 		t.Fatal("physical edits remaining")
 	}
 	w.Flush()
 	f.Close()
 }

 func setOf(keys ...string) map[string]bool {
 	m := make(map[string]bool, len(keys))
 	for _, key := range keys {
 		m[key] = true
 	}
 	return m
 }

 var runtimeFeatures = setOf(
 	"adx", "aes", "avx", "avx2", "bmi1", "bmi2", "erms", "fma",
 	"pclmulqdq", "popcnt", "rdtscp", "sse3", "sse41", "sse42", "ssse3",
 )

 var featureToOpcodes = map[string][]string{
 	// Note: we include *q, *l, and plain opcodes here.
 	// go tool objdump doesn't include a [QL] on popcnt instructions, until CL 351889
 	// native objdump doesn't include [QL] on linux.
 	"popcnt": {"popcntq", "popcntl", "popcnt"},
 	"bmi1":   {"andnq", "andnl", "andn", "blsiq", "blsil", "blsi", "blsmskq", "blsmskl", "blsmsk", "blsrq", "blsrl", "blsr", "tzcntq", "tzcntl", "tzcnt"},
 	"sse41":  {"roundsd"},
 	"fma":    {"vfmadd231sd"},
 	"movbe":  {"movbeqq", "movbeq", "movbell", "movbel", "movbe"},
 }

 // Test to use POPCNT instruction, if available
 func TestPopCnt(t *testing.T) {
 	for _, tt := range []struct {
 		x    uint64
 		want int
 	}{
 		{0b00001111, 4},
 		{0b00001110, 3},
 		{0b00001100, 2},
 		{0b00000000, 0},
 	} {
 		if got := bits.OnesCount64(tt.x); got != tt.want {
 			t.Errorf("OnesCount64(%#x) = %d, want %d", tt.x, got, tt.want)
 		}
 		if got := bits.OnesCount32(uint32(tt.x)); got != tt.want {
 			t.Errorf("OnesCount32(%#x) = %d, want %d", tt.x, got, tt.want)
 		}
 	}
 }

 // Test to use ANDN, if available
 func TestAndNot(t *testing.T) {
 	for _, tt := range []struct {
 		x, y, want uint64
 	}{
 		{0b00001111, 0b00000011, 0b1100},
 		{0b00001111, 0b00001100, 0b0011},
 		{0b00000000, 0b00000000, 0b0000},
 	} {
 		if got := tt.x &^ tt.y; got != tt.want {
 			t.Errorf("%#x &^ %#x = %#x, want %#x", tt.x, tt.y, got, tt.want)
 		}
 		if got := uint32(tt.x) &^ uint32(tt.y); got != uint32(tt.want) {
 			t.Errorf("%#x &^ %#x = %#x, want %#x", tt.x, tt.y, got, tt.want)
 		}
 	}
 }

 // Test to use BLSI, if available
 func TestBLSI(t *testing.T) {
 	for _, tt := range []struct {
 		x, want uint64
 	}{
 		{0b00001111, 0b001},
 		{0b00001110, 0b010},
 		{0b00001100, 0b100},
 		{0b11000110, 0b010},
 		{0b00000000, 0b000},
 	} {
 		if got := tt.x & -tt.x; got != tt.want {
 			t.Errorf("%#x & (-%#x) = %#x, want %#x", tt.x, tt.x, got, tt.want)
 		}
 		if got := uint32(tt.x) & -uint32(tt.x); got != uint32(tt.want) {
 			t.Errorf("%#x & (-%#x) = %#x, want %#x", tt.x, tt.x, got, tt.want)
 		}
 	}
 }

 // Test to use BLSMSK, if available
 func TestBLSMSK(t *testing.T) {
 	for _, tt := range []struct {
 		x, want uint64
 	}{
 		{0b00001111, 0b001},
 		{0b00001110, 0b011},
 		{0b00001100, 0b111},
 		{0b11000110, 0b011},
 		{0b00000000, 1<<64 - 1},
 	} {
 		if got := tt.x ^ (tt.x - 1); got != tt.want {
 			t.Errorf("%#x ^ (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
 		}
 		if got := uint32(tt.x) ^ (uint32(tt.x) - 1); got != uint32(tt.want) {
 			t.Errorf("%#x ^ (%#x-1) = %#x, want %#x", tt.x, tt.x, got, uint32(tt.want))
 		}
 	}
 }

 // Test to use BLSR, if available
 func TestBLSR(t *testing.T) {
 	for _, tt := range []struct {
 		x, want uint64
 	}{
 		{0b00001111, 0b00001110},
 		{0b00001110, 0b00001100},
 		{0b00001100, 0b00001000},
 		{0b11000110, 0b11000100},
 		{0b00000000, 0b00000000},
 	} {
 		if got := tt.x & (tt.x - 1); got != tt.want {
 			t.Errorf("%#x & (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
 		}
 		if got := uint32(tt.x) & (uint32(tt.x) - 1); got != uint32(tt.want) {
 			t.Errorf("%#x & (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
 		}
 	}
 }

 func TestTrailingZeros(t *testing.T) {
 	for _, tt := range []struct {
 		x    uint64
 		want int
 	}{
 		{0b00001111, 0},
 		{0b00001110, 1},
 		{0b00001100, 2},
 		{0b00001000, 3},
 		{0b00000000, 64},
 	} {
 		if got := bits.TrailingZeros64(tt.x); got != tt.want {
 			t.Errorf("TrailingZeros64(%#x) = %d, want %d", tt.x, got, tt.want)
 		}
 		want := tt.want
 		if want == 64 {
 			want = 32
 		}
 		if got := bits.TrailingZeros32(uint32(tt.x)); got != want {
 			t.Errorf("TrailingZeros64(%#x) = %d, want %d", tt.x, got, want)
 		}
 	}
 }

 func TestRound(t *testing.T) {
 	for _, tt := range []struct {
 		x, want float64
 	}{
 		{1.4, 1},
 		{1.5, 2},
 		{1.6, 2},
 		{2.4, 2},
 		{2.5, 2},
 		{2.6, 3},
 	} {
 		if got := math.RoundToEven(tt.x); got != tt.want {
 			t.Errorf("RoundToEven(%f) = %f, want %f", tt.x, got, tt.want)
 		}
 	}
 }

 func TestFMA(t *testing.T) {
 	for _, tt := range []struct {
 		x, y, z, want float64
 	}{
 		{2, 3, 4, 10},
 		{3, 4, 5, 17},
 	} {
 		if got := math.FMA(tt.x, tt.y, tt.z); got != tt.want {
 			t.Errorf("FMA(%f,%f,%f) = %f, want %f", tt.x, tt.y, tt.z, got, tt.want)
 		}
 	}
 }
	// Copyright 2021 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package amd64_test

	import (
	"bufio"
	"debug/elf"
	"debug/macho"
	"fmt"
	"internal/testenv"
	"io"
	"math"
	"math/bits"
	"os"
	"os/exec"
	"regexp"
	"runtime"
	"strconv"
	"strings"
	"testing"
	)

	// Test to make sure that when building for GOAMD64=v1, we don't
	// use any >v1 instructions.
	func TestGoAMD64v1(t *testing.T) {
	if runtime.GOARCH != "amd64" {
	t.Skip("amd64-only test")
	}
	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
	t.Skip("test only works on elf or macho platforms")
	}
	if v := os.Getenv("GOAMD64"); v != "" && v != "v1" {
	// Test runs only on v1 (which is the default).
	// TODO: use build tags from #45454 instead.
	t.Skip("GOAMD64 already set")
	}
	if os.Getenv("TESTGOAMD64V1") != "" {
	t.Skip("recursive call")
	}

	// Make a binary which will be a modified version of the
	// currently running binary.
	dst, err := os.CreateTemp("", "TestGoAMD64v1")
	if err != nil {
	t.Fatalf("failed to create temp file: %v", err)
	}
	defer os.Remove(dst.Name())
	dst.Chmod(0500) // make executable

	// Clobber all the non-v1 opcodes.
	opcodes := map[string]bool{}
	var features []string
	for feature, opcodeList := range featureToOpcodes {
	if runtimeFeatures[feature] {
	features = append(features, fmt.Sprintf("cpu.%s=off", feature))
	}
	for _, op := range opcodeList {
	opcodes[op] = true
	}
	}
	clobber(t, os.Args[0], dst, opcodes)
	if err = dst.Close(); err != nil {
	t.Fatalf("can't close binary: %v", err)
	}

	// Run the resulting binary.
	cmd := exec.Command(dst.Name())
	testenv.CleanCmdEnv(cmd)
	cmd.Env = append(cmd.Env, "TESTGOAMD64V1=yes")
	cmd.Env = append(cmd.Env, fmt.Sprintf("GODEBUG=%s", strings.Join(features, ",")))
	out, err := cmd.CombinedOutput()
	if err != nil {
	t.Fatalf("couldn't execute test: %s", err)
	}
	if string(out) != "PASS\n" {
	t.Fatalf("test reported error: %s", string(out))
	}
	}

	// Clobber copies the binary src to dst, replacing all the instructions in opcodes with
	// faulting instructions.
	func clobber(t testing.T, src string, dst os.File, opcodes map[string]bool) {
	// Run objdump to get disassembly.
	var re *regexp.Regexp
	var disasm io.Reader
	if false {
	// TODO: go tool objdump doesn't disassemble the bmi1 instructions
	// in question correctly. See issue 48584.
	cmd := exec.Command("go", "tool", "objdump", src)
	var err error
	disasm, err = cmd.StdoutPipe()
	if err != nil {
	t.Fatal(err)
	}
	if err := cmd.Start(); err != nil {
	t.Fatal(err)
	}
	re = regexp.MustCompile(`^[^:]*:[-0-9]+\s+0x([0-9a-f]+)\s+([0-9a-f]+)\s+([A-Z]+)`)
	} else {
	// TODO: we're depending on platform-native objdump here. Hence the Skipf
	// below if it doesn't run for some reason.
	cmd := exec.Command("objdump", "-d", src)
	var err error
	disasm, err = cmd.StdoutPipe()
	if err != nil {
	t.Skipf("can't run test due to missing objdump: %s", err)
	}
	if err := cmd.Start(); err != nil {
	t.Fatal(err)
	}
	re = regexp.MustCompile(`^\s([0-9a-f]+):\s((?:[0-9a-f][0-9a-f] )+)\s*([a-z0-9]+)`)
	}

	// Find all the instruction addresses we need to edit.
	virtualEdits := map[uint64]bool{}
	scanner := bufio.NewScanner(disasm)
	for scanner.Scan() {
	line := scanner.Text()
	parts := re.FindStringSubmatch(line)
	if len(parts) == 0 {
	continue
	}
	addr, err := strconv.ParseUint(parts[1], 16, 64)
	if err != nil {
	continue // not a hex address
	}
	opcode := strings.ToLower(parts[3])
	if !opcodes[opcode] {
	continue
	}
	t.Logf("clobbering instruction %s", line)
	n := (len(parts[2]) - strings.Count(parts[2], " ")) / 2 // number of bytes in instruction encoding
	for i := 0; i < n; i++ {
	// Only really need to make the first byte faulting, but might
	// as well make all the bytes faulting.
	virtualEdits[addr+uint64(i)] = true
	}
	}

	// Figure out where in the binary the edits must be done.
	physicalEdits := map[uint64]bool{}
	if e, err := elf.Open(src); err == nil {
	for _, sec := range e.Sections {
	vaddr := sec.Addr
	paddr := sec.Offset
	size := sec.Size
	for a := range virtualEdits {
	if a >= vaddr && a < vaddr+size {
	physicalEdits[paddr+(a-vaddr)] = true
	}
	}
	}
	} else if m, err2 := macho.Open(src); err2 == nil {
	for _, sec := range m.Sections {
	vaddr := sec.Addr
	paddr := uint64(sec.Offset)
	size := sec.Size
	for a := range virtualEdits {
	if a >= vaddr && a < vaddr+size {
	physicalEdits[paddr+(a-vaddr)] = true
	}
	}
	}
	} else {
	t.Log(err)
	t.Log(err2)
	t.Fatal("executable format not elf or macho")
	}
	if len(virtualEdits) != len(physicalEdits) {
	t.Fatal("couldn't find an instruction in text sections")
	}

	// Copy source to destination, making edits along the way.
	f, err := os.Open(src)
	if err != nil {
	t.Fatal(err)
	}
	r := bufio.NewReader(f)
	w := bufio.NewWriter(dst)
	a := uint64(0)
	done := 0
	for {
	b, err := r.ReadByte()
	if err == io.EOF {
	break
	}
	if err != nil {
	t.Fatal("can't read")
	}
	if physicalEdits[a] {
	b = 0xcc // INT3 opcode
	done++
	}
	err = w.WriteByte(b)
	if err != nil {
	t.Fatal("can't write")
	}
	a++
	}
	if done != len(physicalEdits) {
	t.Fatal("physical edits remaining")
	}
	w.Flush()
	f.Close()
	}

	func setOf(keys ...string) map[string]bool {
	m := make(map[string]bool, len(keys))
	for _, key := range keys {
	m[key] = true
	}
	return m
	}

	var runtimeFeatures = setOf(
	"adx", "aes", "avx", "avx2", "bmi1", "bmi2", "erms", "fma",
	"pclmulqdq", "popcnt", "rdtscp", "sse3", "sse41", "sse42", "ssse3",
	)

	var featureToOpcodes = map[string][]string{
	// Note: we include q, l, and plain opcodes here.
	// go tool objdump doesn't include a [QL] on popcnt instructions, until CL 351889
	// native objdump doesn't include [QL] on linux.
	"popcnt": {"popcntq", "popcntl", "popcnt"},
	"bmi1": {"andnq", "andnl", "andn", "blsiq", "blsil", "blsi", "blsmskq", "blsmskl", "blsmsk", "blsrq", "blsrl", "blsr", "tzcntq", "tzcntl", "tzcnt"},
	"sse41": {"roundsd"},
	"fma": {"vfmadd231sd"},
	"movbe": {"movbeqq", "movbeq", "movbell", "movbel", "movbe"},
	}

	// Test to use POPCNT instruction, if available
	func TestPopCnt(t *testing.T) {
	for _, tt := range []struct {
	x uint64
	want int
	}{
	{0b00001111, 4},
	{0b00001110, 3},
	{0b00001100, 2},
	{0b00000000, 0},
	} {
	if got := bits.OnesCount64(tt.x); got != tt.want {
	t.Errorf("OnesCount64(%#x) = %d, want %d", tt.x, got, tt.want)
	}
	if got := bits.OnesCount32(uint32(tt.x)); got != tt.want {
	t.Errorf("OnesCount32(%#x) = %d, want %d", tt.x, got, tt.want)
	}
	}
	}

	// Test to use ANDN, if available
	func TestAndNot(t *testing.T) {
	for _, tt := range []struct {
	x, y, want uint64
	}{
	{0b00001111, 0b00000011, 0b1100},
	{0b00001111, 0b00001100, 0b0011},
	{0b00000000, 0b00000000, 0b0000},
	} {
	if got := tt.x &^ tt.y; got != tt.want {
	t.Errorf("%#x &^ %#x = %#x, want %#x", tt.x, tt.y, got, tt.want)
	}
	if got := uint32(tt.x) &^ uint32(tt.y); got != uint32(tt.want) {
	t.Errorf("%#x &^ %#x = %#x, want %#x", tt.x, tt.y, got, tt.want)
	}
	}
	}

	// Test to use BLSI, if available
	func TestBLSI(t *testing.T) {
	for _, tt := range []struct {
	x, want uint64
	}{
	{0b00001111, 0b001},
	{0b00001110, 0b010},
	{0b00001100, 0b100},
	{0b11000110, 0b010},
	{0b00000000, 0b000},
	} {
	if got := tt.x & -tt.x; got != tt.want {
	t.Errorf("%#x & (-%#x) = %#x, want %#x", tt.x, tt.x, got, tt.want)
	}
	if got := uint32(tt.x) & -uint32(tt.x); got != uint32(tt.want) {
	t.Errorf("%#x & (-%#x) = %#x, want %#x", tt.x, tt.x, got, tt.want)
	}
	}
	}

	// Test to use BLSMSK, if available
	func TestBLSMSK(t *testing.T) {
	for _, tt := range []struct {
	x, want uint64
	}{
	{0b00001111, 0b001},
	{0b00001110, 0b011},
	{0b00001100, 0b111},
	{0b11000110, 0b011},
	{0b00000000, 1<<64 - 1},
	} {
	if got := tt.x ^ (tt.x - 1); got != tt.want {
	t.Errorf("%#x ^ (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
	}
	if got := uint32(tt.x) ^ (uint32(tt.x) - 1); got != uint32(tt.want) {
	t.Errorf("%#x ^ (%#x-1) = %#x, want %#x", tt.x, tt.x, got, uint32(tt.want))
	}
	}
	}

	// Test to use BLSR, if available
	func TestBLSR(t *testing.T) {
	for _, tt := range []struct {
	x, want uint64
	}{
	{0b00001111, 0b00001110},
	{0b00001110, 0b00001100},
	{0b00001100, 0b00001000},
	{0b11000110, 0b11000100},
	{0b00000000, 0b00000000},
	} {
	if got := tt.x & (tt.x - 1); got != tt.want {
	t.Errorf("%#x & (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
	}
	if got := uint32(tt.x) & (uint32(tt.x) - 1); got != uint32(tt.want) {
	t.Errorf("%#x & (%#x-1) = %#x, want %#x", tt.x, tt.x, got, tt.want)
	}
	}
	}

	func TestTrailingZeros(t *testing.T) {
	for _, tt := range []struct {
	x uint64
	want int
	}{
	{0b00001111, 0},
	{0b00001110, 1},
	{0b00001100, 2},
	{0b00001000, 3},
	{0b00000000, 64},
	} {
	if got := bits.TrailingZeros64(tt.x); got != tt.want {
	t.Errorf("TrailingZeros64(%#x) = %d, want %d", tt.x, got, tt.want)
	}
	want := tt.want
	if want == 64 {
	want = 32
	}
	if got := bits.TrailingZeros32(uint32(tt.x)); got != want {
	t.Errorf("TrailingZeros64(%#x) = %d, want %d", tt.x, got, want)
	}
	}
	}

	func TestRound(t *testing.T) {
	for _, tt := range []struct {
	x, want float64
	}{
	{1.4, 1},
	{1.5, 2},
	{1.6, 2},
	{2.4, 2},
	{2.5, 2},
	{2.6, 3},
	} {
	if got := math.RoundToEven(tt.x); got != tt.want {
	t.Errorf("RoundToEven(%f) = %f, want %f", tt.x, got, tt.want)
	}
	}
	}

	func TestFMA(t *testing.T) {
	for _, tt := range []struct {
	x, y, z, want float64
	}{
	{2, 3, 4, 10},
	{3, 4, 5, 17},
	} {
	if got := math.FMA(tt.x, tt.y, tt.z); got != tt.want {
	t.Errorf("FMA(%f,%f,%f) = %f, want %f", tt.x, tt.y, tt.z, got, tt.want)
	}
	}
	}