runtime: make nanotime use monotonic clock in Solaris

nanotime() currently uses the REALTIME clock to get the elapsed
time in Solaris. This commit changes it to use the MONOTONIC clock
instead, similar to how it's done in Linux and other OSs. Also changed
nanotime() and walltime() to call clock_gettime() library function
directly from Go code rather than from assembly.

Fixes #33674

Change-Id: Ie4a687b17d2140998ecd97af6ce048c86cf5fc02
Reviewed-on: https://go-review.googlesource.com/c/go/+/199502
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

src/runtime/os3_solaris.go

@@ -393,11 +393,16 @@ func munmap(addr unsafe.Pointer, n uintptr) {
 	sysvicall2(&libc_munmap, uintptr(addr), uintptr(n))
 }
 
-func nanotime2()
+const (
+	_CLOCK_REALTIME  = 3
+	_CLOCK_MONOTONIC = 4
+)
 
 //go:nosplit
 func nanotime1() int64 {
-	return int64(sysvicall0((*libcFunc)(unsafe.Pointer(funcPC(nanotime2)))))
+	var ts mts
+	sysvicall2(&libc_clock_gettime, _CLOCK_MONOTONIC, uintptr(unsafe.Pointer(&ts)))
+	return ts.tv_sec*1e9 + ts.tv_nsec
 }
 
 //go:nosplit
@@ -498,6 +503,12 @@ func usleep(µs uint32) {
 	usleep1(µs)
 }
 
+func walltime1() (sec int64, nsec int32) {
+	var ts mts
+	sysvicall2(&libc_clock_gettime, _CLOCK_REALTIME, uintptr(unsafe.Pointer(&ts)))
+	return ts.tv_sec, int32(ts.tv_nsec)
+}
+
 //go:nosplit
 func write1(fd uintptr, buf unsafe.Pointer, nbyte int32) int32 {
 	return int32(sysvicall3(&libc_write, uintptr(fd), uintptr(buf), uintptr(nbyte)))

src/runtime/sys_solaris_amd64.s

@@ -29,26 +29,6 @@ TEXT runtime·miniterrno(SB),NOSPLIT,$0
 	MOVQ	AX,	(m_mOS+mOS_perrno)(BX)
 	RET
 
-// int64 runtime·nanotime2(void);
-//
-// clock_gettime(3c) wrapper because Timespec is too large for
-// runtime·nanotime stack.
-//
-// Called using runtime·sysvicall6 from os_solaris.c:/nanotime.
-// NOT USING GO CALLING CONVENTION.
-TEXT runtime·nanotime2(SB),NOSPLIT,$0
-	// need space for the timespec argument.
-	SUBQ	$64, SP	// 16 bytes will do, but who knows in the future?
-	MOVQ	$3, DI	// CLOCK_REALTIME from <sys/time_impl.h>
-	MOVQ	SP, SI
-	LEAQ	libc_clock_gettime(SB), AX
-	CALL	AX
-	MOVQ	(SP), AX	// tv_sec from struct timespec
-	IMULQ	$1000000000, AX	// multiply into nanoseconds
-	ADDQ	8(SP), AX	// tv_nsec, offset should be stable.
-	ADDQ	$64, SP
-	RET
-
 // pipe(3c) wrapper that returns fds in AX, DX.
 // NOT USING GO CALLING CONVENTION.
 TEXT runtime·pipe1(SB),NOSPLIT,$0
@@ -338,23 +318,3 @@ TEXT runtime·osyield1(SB),NOSPLIT,$0
 	LEAQ	libc_sched_yield(SB), AX
 	CALL	AX
 	RET
-
-// func walltime1() (sec int64, nsec int32)
-TEXT runtime·walltime1(SB),NOSPLIT,$8-12
-	CALL	runtime·nanotime1(SB)
-	MOVQ	0(SP), AX
-
-	// generated code for
-	//	func f(x uint64) (uint64, uint64) { return x/1000000000, x%100000000 }
-	// adapted to reduce duplication
-	MOVQ	AX, CX
-	MOVQ	$1360296554856532783, AX
-	MULQ	CX
-	ADDQ	CX, DX
-	RCRQ	$1, DX
-	SHRQ	$29, DX
-	MOVQ	DX, sec+0(FP)
-	IMULQ	$1000000000, DX
-	SUBQ	DX, CX
-	MOVL	CX, nsec+8(FP)
-	RET

src/runtime/timestub2.go

@@ -6,6 +6,7 @@
 // +build !windows
 // +build !freebsd
 // +build !aix
+// +build !solaris
 
 package runtime