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runtime: delete timediv

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Now that the compiler handles constant 64-bit divisions
without function calls on 32-bit systems, we no longer need
to maintain and test a bad custom implementation of 64-bit division.

Change-Id: If28807ad4f86507267ae69bc8f0b09ec18e98b66
Reviewed-on: https://go-review.googlesource.com/c/go/+/716463
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Russ Cox 2025-10-29 13:37:52 -04:00 • committed by Gopher Robot
parent cbbd385cb8
commit d32b1f02c3
15 changed files with 27 additions and 132 deletions
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3
src/runtime/defs1_netbsd_386.go
View file

@ -121,7 +121,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

3
src/runtime/defs1_netbsd_arm.go
View file

@ -123,7 +123,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

3
src/runtime/defs_freebsd_386.go
View file

@ -210,7 +210,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
ts.tv_sec = int32(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

3
src/runtime/defs_freebsd_arm.go
View file

@ -182,7 +182,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

8
src/runtime/defs_linux_386.go
View file

@ -146,7 +146,8 @@ type timespec32 struct {
//go:nosplit
func (ts *timespec32) setNsec(ns int64) {
ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
ts.tv_sec = int32(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timespec struct {
@ -156,9 +157,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
var newNS int32
ts.tv_sec = int64(timediv(ns, 1e9, &newNS))
ts.tv_nsec = int64(newNS)
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int64(ns % 1e9)
}
type timeval struct {

8
src/runtime/defs_linux_arm.go
View file

@ -105,7 +105,8 @@ type timespec32 struct {
//go:nosplit
func (ts *timespec32) setNsec(ns int64) {
ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
ts.tv_sec = int32(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timespec struct {
@ -115,9 +116,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
var newNS int32
ts.tv_sec = int64(timediv(ns, 1e9, &newNS))
ts.tv_nsec = int64(newNS)
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int64(ns % 1e9)
}
type stackt struct {

8
src/runtime/defs_linux_mipsx.go
View file

@ -103,7 +103,8 @@ type timespec32 struct {
//go:nosplit
func (ts *timespec32) setNsec(ns int64) {
ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
ts.tv_sec = int32(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timespec struct {
@ -113,9 +114,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
var newNS int32
ts.tv_sec = int64(timediv(ns, 1e9, &newNS))
ts.tv_nsec = int64(newNS)
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int64(ns % 1e9)
}
type timeval struct {

3
src/runtime/defs_openbsd_386.go
View file

@ -147,7 +147,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

3
src/runtime/defs_openbsd_arm.go
View file

@ -152,7 +152,8 @@ type timespec struct {
//go:nosplit
func (ts *timespec) setNsec(ns int64) {
ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
ts.tv_sec = int64(ns / 1e9)
ts.tv_nsec = int32(ns % 1e9)
}
type timeval struct {

2
src/runtime/export_test.go
View file

@ -1472,8 +1472,6 @@ func Releasem() {
releasem(getg().m)
}
var Timediv = timediv
type PIController struct {
piController
}

2
src/runtime/os_dragonfly.go
View file

@ -113,7 +113,7 @@ func futexsleep1(addr *uint32, val uint32, ns int64) {
// The timeout is specified in microseconds - ensure that we
// do not end up dividing to zero, which would put us to sleep
// indefinitely...
timeout = timediv(ns, 1000, nil)
timeout = int32(ns / 1000)
if timeout == 0 {
timeout = 1
}

2
src/runtime/os_plan9.go
View file

@ -486,7 +486,7 @@ func semacreate(mp *m) {
func semasleep(ns int64) int {
gp := getg()
if ns >= 0 {
ms := timediv(ns, 1000000, nil)
ms := int32(ns / 1000000)
if ms == 0 {
ms = 1
}

2
src/runtime/os_windows.go
View file

@ -664,7 +664,7 @@ func semasleep(ns int64) int32 {
start := nanotime()
elapsed := int64(0)
for {
ms := int64(timediv(ns-elapsed, 1000000, nil))
ms := (ns - elapsed) / 1000000
if ms == 0 {
ms = 1
}

33
src/runtime/runtime1.go
View file

@ -212,10 +212,6 @@ func check() {
throw("bad unsafe.Sizeof y1")
}
if timediv(12345*1000000000+54321, 1000000000, &e) != 12345 || e != 54321 {
throw("bad timediv")
}
var z uint32
z = 1
if !atomic.Cas(&z, 1, 2) {
@ -593,35 +589,6 @@ func setTraceback(level string) {
atomic.Store(&traceback_cache, t)
}
// Poor mans 64-bit division.
// This is a very special function, do not use it if you are not sure what you are doing.
// int64 division is lowered into _divv() call on 386, which does not fit into nosplit functions.
// Handles overflow in a time-specific manner.
// This keeps us within no-split stack limits on 32-bit processors.
//
//go:nosplit
func timediv(v int64, div int32, rem *int32) int32 {
res := int32(0)
for bit := 30; bit >= 0; bit-- {
if v >= int64(div)<<uint(bit) {
v = v - (int64(div) << uint(bit))
// Before this for loop, res was 0, thus all these
// power of 2 increments are now just bitsets.
res |= 1 << uint(bit)
}
}
if v >= int64(div) {
if rem != nil {
*rem = 0
}
return 0x7fffffff
}
if rem != nil {
*rem = int32(v)
}
return res
}
// Helpers for Go. Must be NOSPLIT, must only call NOSPLIT functions, and must not block.
//go:nosplit

76
src/runtime/runtime_test.go
View file

@ -6,7 +6,6 @@ package runtime_test
import (
"flag"
"fmt"
"internal/asan"
"internal/cpu"
"internal/msan"
@ -498,81 +497,6 @@ func TestVersion(t *testing.T) {
}
}
func TestTimediv(t *testing.T) {
for _, tc := range []struct {
num int64
div int32
ret int32
rem int32
}{
{
num: 8,
div: 2,
ret: 4,
rem: 0,
},
{
num: 9,
div: 2,
ret: 4,
rem: 1,
},
{
// Used by runtime.check.
num: 12345*1000000000 + 54321,
div: 1000000000,
ret: 12345,
rem: 54321,
},
{
num: 1<<32 - 1,
div: 2,
ret: 1<<31 - 1, // no overflow.
rem: 1,
},
{
num: 1 << 32,
div: 2,
ret: 1<<31 - 1, // overflow.
rem: 0,
},
{
num: 1 << 40,
div: 2,
ret: 1<<31 - 1, // overflow.
rem: 0,
},
{
num: 1<<40 + 1,
div: 1 << 10,
ret: 1 << 30,
rem: 1,
},
} {
name := fmt.Sprintf("%d div %d", tc.num, tc.div)
t.Run(name, func(t *testing.T) {
// Double check that the inputs make sense using
// standard 64-bit division.
ret64 := tc.num / int64(tc.div)
rem64 := tc.num % int64(tc.div)
if ret64 != int64(int32(ret64)) {
// Simulate timediv overflow value.
ret64 = 1<<31 - 1
rem64 = 0
}
if ret64 != int64(tc.ret) {
t.Errorf("%d / %d got ret %d rem %d want ret %d rem %d", tc.num, tc.div, ret64, rem64, tc.ret, tc.rem)
}
var rem int32
ret := Timediv(tc.num, tc.div, &rem)
if ret != tc.ret || rem != tc.rem {
t.Errorf("timediv %d / %d got ret %d rem %d want ret %d rem %d", tc.num, tc.div, ret, rem, tc.ret, tc.rem)
}
})
}
}
func BenchmarkProcYield(b *testing.B) {
benchN := func(n uint32) func(*testing.B) {
return func(b *testing.B) {