Set hours string in a single memory access

wtfstopw.asm

 	SIGACTION sigaction
 
 	align 8
-	hours: times 8 db '0' ; allows storing max hours in 1<<64 secs
+	hours: times 8 db '0' ; 8 digits is the max for hours
 	timestr: db ":00:00." 
-		times 8 db '0'
+		times 8 db '0' ; 8 digits for nanoseconds
 		times 0xE db ' '
 		db 0
 	timestrend: align 8
 	timestrlen: equ timestrend - timestr
-	hourslen: equ timestr - hours ; hours len -> the max number of digits
+	%define HOURSLEN 8
 
 	lapsmsg: db "Lap : "
 	lapsmsglen: equ $ - lapsmsg
 	xor rdx, rdx
 	div qword [ts_sleep.tv_nsec] ; Divide result given time_res
 
+	mov r9, [rsp + 8]
+	mov byte [timestr+timestrlen-1], r9b ; set last chr from 1st argument
+
 	; set the nanosec chars (time_res chars) in timestr
 	mov rbx, 0x2020202020202020
 	mov rcx, [time_res]
 	procpt_loopns:
 		xor rdx, rdx
 		div r8
-		add dl, '0'
+		or dl, 0x30 ; '0'
 		shl rbx, 8
 		mov bl, dl
 		loop procpt_loopns
 	xor dl, dl
 	div r9
 	mov bl, dl
-	add bx, 0x3030
+	or bx, 0x3030
 	mov word [timestr + 4], bx
 
 	xor dl, dl
 	xor dl, dl
 	div r9
 	mov bl, dl
-	add bx, 0x3030
+	or bx, 0x3030
 	mov word [timestr + 1], bx
 
-	; filling the hours buffer
-	; rcx will contain max_digits - digits_count
-	; digits max is hourslen - 1
-	mov rcx, hourslen - 1
-	mov rdi, hours + hourslen - 1
-	mov r10, 10
-	procpt_loop:
+	; using rbx to stores the hours string
+	xor rbx, rbx
+	mov rcx, HOURSLEN
+	mov r8, 10
+	procpt_looph:
 		xor dl, dl
-		div r10
-		cmp rax, 0
-		jne procpt_loopcont
-		cmp dl, 0
-		je procpt_loop_end
-
-		procpt_loopcont:
-		xchg al, dl
-		add al, 0x30
-		stosb
-		mov al, dl
-		cmp rcx, 0
-		je fault
+		div r8
+		shl rbx, 8
+		mov bl, dl
 		cmp rax, 0
-		loopne procpt_loop
-	procpt_loop_end:
-
-	; set rcx for 2 digits at least for hours
-	mov r9, hourslen - 2
-	add rcx, 1
-	cmp rcx, r9
-	cmovnle rcx, r9
+		loopne procpt_looph
+	procpt_looph_end:
+
+	mov r8, HOURSLEN - 2
+	cmp rcx, HOURSLEN - 2
+	cmovl r8, rcx ; r8 stores hours digit count (at least 2)
+	cmp rcx, 0
+	jz procpt_looph2_end
+	procpt_looph2:
+		shl rbx, 8
+		loopne procpt_looph2
+	procpt_looph2_end:
 
-	mov r10, [rsp + 8] ; leading chr as 1st argument
-	mov byte [timestr+timestrlen-1], r10b
+	mov r9, 0x3030303030303030 ; ASCII convertion
+	or rbx, r9
+	mov [hours], rbx
 
 	mov rax, 1 ; write
 	mov rdi, [rsp + 16] ; fd as 2nd argument
-	mov rdx, timestrlen + hourslen
-	sub rdx, rcx ; timestr + hours len
-	lea rsi, [hours + rcx] ; hours start pointer
+	lea rsi, [hours + r8] ; hours start pointer
+	mov rdx, timestrlen + HOURSLEN
+	sub rdx, r8 ; timestr + hours len
 	syscall
 
 	ret 16