runtime: introduce and consistently use setNsec for timespec

The general code for setting a timespec value sometimes used set_nsec
and sometimes used a combination of set_sec and set_nsec. Standardize
on a setNsec function that takes a number of nanoseconds and splits
them up to set the tv_sec and tv_nsec fields. Consistently mark
setNsec as go:nosplit, since it has to be that way on some systems
including Darwin and GNU/Linux. Consistently use timediv on 32-bit
systems to help stay within split-stack limits on processors that
don't have a 64-bit division instruction.

Change-Id: I6396bb7ddbef171a96876bdeaf7a1c585a6d725b
Reviewed-on: https://go-review.googlesource.com/c/go/+/167389
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/defs1_netbsd_386.go

@@ -106,12 +106,9 @@ type timespec struct {
 	tv_nsec int32
 }
 
-func (ts *timespec) set_sec(x int32) {
-	ts.tv_sec = int64(x)
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
 }
 
 type timeval struct {

src/runtime/defs1_netbsd_amd64.go

@@ -108,12 +108,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int32) {
-	ts.tv_sec = int64(x)
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs1_netbsd_arm.go

@@ -108,12 +108,9 @@ type timespec struct {
 	_       [4]byte // EABI
 }
 
-func (ts *timespec) set_sec(x int32) {
-	ts.tv_sec = int64(x)
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
 }
 
 type timeval struct {

src/runtime/defs1_solaris_amd64.go

@@ -161,6 +161,12 @@ type timespec struct {
 	tv_nsec int64
 }
 
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
+}
+
 type timeval struct {
 	tv_sec  int64
 	tv_usec int64

src/runtime/defs_aix_ppc64.go

@@ -126,6 +126,13 @@ type timespec struct {
 	tv_sec  int64
 	tv_nsec int64
 }
+
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
+}
+
 type timeval struct {
 	tv_sec    int64
 	tv_usec   int32

src/runtime/defs_darwin_386.go

@@ -149,9 +149,8 @@ type timespec struct {
 }
 
 //go:nosplit
-func (t *timespec) set_nsec(ns int64) {
-	t.tv_sec = int32(ns / 1000000000)
-	t.tv_nsec = int32(ns % 1000000000)
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type fpcontrol struct {

src/runtime/defs_darwin_amd64.go

@@ -151,9 +151,9 @@ type timespec struct {
 }
 
 //go:nosplit
-func (t *timespec) set_nsec(ns int64) {
-	t.tv_sec = ns / 1000000000
-	t.tv_nsec = ns % 1000000000
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type fpcontrol struct {

src/runtime/defs_darwin_arm.go

@@ -151,9 +151,8 @@ type timespec struct {
 }
 
 //go:nosplit
-func (t *timespec) set_nsec(ns int64) {
-	t.tv_sec = int32(ns / 1000000000)
-	t.tv_nsec = int32(ns % 1000000000)
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type floatstate32 struct {

src/runtime/defs_darwin_arm64.go

@@ -151,9 +151,9 @@ type timespec struct {
 }
 
 //go:nosplit
-func (t *timespec) set_nsec(ns int64) {
-	t.tv_sec = ns / 1000000000
-	t.tv_nsec = ns % 1000000000
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type exceptionstate64 struct {

src/runtime/defs_dragonfly_amd64.go

@@ -174,8 +174,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_freebsd_386.go

@@ -191,8 +191,9 @@ type timespec struct {
 	tv_nsec int32
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = int32(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type timeval struct {

src/runtime/defs_freebsd_amd64.go

@@ -201,8 +201,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_freebsd_arm.go

@@ -163,8 +163,9 @@ type timespec struct {
 	pad_cgo_0 [4]byte
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
 }
 
 type timeval struct {

src/runtime/defs_linux_386.go

@@ -137,12 +137,9 @@ type timespec struct {
 	tv_nsec int32
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = int32(x)
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type timeval struct {

src/runtime/defs_linux_amd64.go

@@ -99,12 +99,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_linux_arm.go

@@ -94,12 +94,9 @@ type timespec struct {
 	tv_nsec int32
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = int32(x)
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type stackt struct {

src/runtime/defs_linux_arm64.go

@@ -99,12 +99,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_linux_mips64x.go

@@ -99,12 +99,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_linux_mipsx.go

@@ -99,13 +99,8 @@ type timespec struct {
 }
 
 //go:nosplit
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = int32(x)
-}
-
-//go:nosplit
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
 type timeval struct {

src/runtime/defs_linux_ppc64.go

@@ -99,12 +99,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_linux_ppc64le.go

@@ -99,12 +99,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_linux_s390x.go

@@ -95,12 +95,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_nacl_386.go

@@ -14,6 +14,11 @@ type timespec struct {
 	tv_nsec int32
 }
 
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
+}
+
 type excregs386 struct {
 	eax    uint32
 	ecx    uint32

src/runtime/defs_nacl_amd64p32.go

@@ -14,6 +14,12 @@ type timespec struct {
 	tv_nsec int32
 }
 
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = int32(ns % 1e9)
+}
+
 type excregs386 struct {
 	eax    uint32
 	ecx    uint32

src/runtime/defs_nacl_arm.go

@@ -14,6 +14,11 @@ type timespec struct {
 	tv_nsec int32
 }
 
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
+}
+
 type excregsarm struct {
 	r0   uint32
 	r1   uint32

src/runtime/defs_openbsd_386.go

@@ -134,12 +134,9 @@ type timespec struct {
 	tv_nsec int32
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
 }
 
 type timeval struct {

src/runtime/defs_openbsd_amd64.go

@@ -144,12 +144,10 @@ type timespec struct {
 	tv_nsec int64
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = int64(x)
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = ns / 1e9
+	ts.tv_nsec = ns % 1e9
 }
 
 type timeval struct {

src/runtime/defs_openbsd_arm.go

@@ -139,12 +139,9 @@ type timespec struct {
 	pad_cgo_0 [4]byte
 }
 
-func (ts *timespec) set_sec(x int64) {
-	ts.tv_sec = x
-}
-
-func (ts *timespec) set_nsec(x int32) {
-	ts.tv_nsec = x
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	ts.tv_sec = int64(timediv(ns, 1e9, &ts.tv_nsec))
 }
 
 type timeval struct {

src/runtime/os_darwin.go

@@ -53,7 +53,7 @@ func semasleep(ns int64) int32 {
 				return -1
 			}
 			var t timespec
-			t.set_nsec(ns - spent)
+			t.setNsec(ns - spent)
 			err := pthread_cond_timedwait_relative_np(&mp.cond, &mp.mutex, &t)
 			if err == _ETIMEDOUT {
 				pthread_mutex_unlock(&mp.mutex)

src/runtime/os_freebsd.go

@@ -156,7 +156,7 @@ func futexsleep1(addr *uint32, val uint32, ns int64) {
 	if ns >= 0 {
 		var ut umtx_time
 		ut._clockid = _CLOCK_MONOTONIC
-		ut._timeout.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ut._timeout.tv_nsec)))))
+		ut._timeout.setNsec(ns)
 		utp = &ut
 	}
 	ret := sys_umtx_op(addr, _UMTX_OP_WAIT_UINT_PRIVATE, val, unsafe.Sizeof(*utp), utp)

src/runtime/os_linux.go

@@ -35,8 +35,6 @@ const (
 // Don't sleep longer than ns; ns < 0 means forever.
 //go:nosplit
 func futexsleep(addr *uint32, val uint32, ns int64) {
-	var ts timespec
-
 	// Some Linux kernels have a bug where futex of
 	// FUTEX_WAIT returns an internal error code
 	// as an errno. Libpthread ignores the return value
@@ -47,19 +45,8 @@ func futexsleep(addr *uint32, val uint32, ns int64) {
 		return
 	}
 
-	// It's difficult to live within the no-split stack limits here.
-	// On ARM and 386, a 64-bit divide invokes a general software routine
-	// that needs more stack than we can afford. So we use timediv instead.
-	// But on real 64-bit systems, where words are larger but the stack limit
-	// is not, even timediv is too heavy, and we really need to use just an
-	// ordinary machine instruction.
-	if sys.PtrSize == 8 {
-		ts.set_sec(ns / 1000000000)
-		ts.set_nsec(int32(ns % 1000000000))
-	} else {
-		ts.tv_nsec = 0
-		ts.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ts.tv_nsec)))))
-	}
+	var ts timespec
+	ts.setNsec(ns)
 	futex(unsafe.Pointer(addr), _FUTEX_WAIT_PRIVATE, val, unsafe.Pointer(&ts), nil, 0)
 }
 

src/runtime/os_netbsd.go

@@ -148,9 +148,7 @@ func semasleep(ns int64) int32 {
 			if wait <= 0 {
 				return -1
 			}
-			var nsec int32
-			ts.set_sec(timediv(wait, 1000000000, &nsec))
-			ts.set_nsec(nsec)
+			ts.setNsec(wait)
 			tsp = &ts
 		}
 		ret := lwp_park(_CLOCK_MONOTONIC, _TIMER_RELTIME, tsp, 0, unsafe.Pointer(&_g_.m.waitsemacount), nil)

src/runtime/os_openbsd.go

@@ -139,10 +139,7 @@ func semasleep(ns int64) int32 {
 	var tsp *timespec
 	if ns >= 0 {
 		var ts timespec
-		var nsec int32
-		ns += nanotime()
-		ts.set_sec(int64(timediv(ns, 1000000000, &nsec)))
-		ts.set_nsec(nsec)
+		ts.setNsec(ns + nanotime())
 		tsp = &ts
 	}
 

src/runtime/runtime1.go

@@ -412,6 +412,7 @@ func setTraceback(level string) {
 // 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)