[swift-evolution] A proposal for inline assembly

[Félix Cloutier]

Do you have a use case for writing a whole assembly program in a .swift file rather than in an assembly file?

> Le 3 déc. 2016 à 15:12, Ethin Probst via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> Hello all,
> My name is Ethin and I am new to this community. However, I certainly
> am no newbie when it comes to software development, and have emailed
> all of you to file a proposal of inline assembly in Swift. The
> assembly language would be within an asm {...} block. The asm keyword
> could also take an optional argument: the type of assembler to use. As
> there are many different types of assemblers out there, I thought this
> should be implemented as well. Furthermore, the asm keyword could also
> take a second optional argument: the extra arguments to pass to the
> assembler. The full syntax of the keyword would look something like:
> asm (assembler, assembler_args)
> {
>    // asm goes here...
> }
> For instance, below is a hello world application in NASM assembly
> language (taken from Wikipedia) with no extra arguments for Linux:
> asm ("nasm")
> {
> global _start
> 
> section .text
> _start:
> 	mov	eax, 4 ; write
> 	mov	ebx, 1 ; stdout
> 	mov	ecx, msg
> 	mov	edx, msg.len
> 	int	0x80   ; write(stdout, msg, strlen(msg));
> 
> 	mov	eax, 1 ; exit
> 	mov	ebx, 0
> 	int	0x80   ; exit(0)
> 
> section .data
> msg:	db	"Hello, world!", 10
> .len:	equ	$ - msg
> }
> And here is one for Mac OS X with the -G, -Fstabs, and -felf arguments to nasm:
> asm ("nasm", "-G -Fstabs -felf")
> {
> global _start
> 
> section .data
> 
> 	query_string:		db	"Enter a character:  "
> 	query_string_len:	equ	$ - query_string
> 	out_string:			db	"You have input:  "
> 	out_string_len:		equ	$ - out_string
> 
> section .bss
> 
> 	in_char:			resw 4
> 
> section .text
> 
> _start:
> 
> 	mov	rax, 0x2000004	 	; put the write-system-call-code into register rax
> 	mov	rdi, 1				; tell kernel to use stdout
> 	mov	rsi, query_string	; rsi is where the kernel expects to find the
> address of the message
> 	mov	rdx, query_string_len	; and rdx is where the kernel expects to
> find the length of the message
> 	syscall
> 
> 	; read in the character
> 	mov	rax, 0x2000003		; read system call
> 	mov	rdi, 0				; stdin
> 	mov	rsi, in_char		; address for storage, declared in section .bss
> 	mov	rdx, 2				; get 2 bytes from the kernel's buffer (one for the
> carriage return)
> 	syscall
> 
> 	; show user the output
> 	mov	rax, 0x2000004		; write system call
> 	mov	rdi, 1				; stdout
> 	mov	rsi, out_string
> 	mov	rdx, out_string_len
> 	syscall
> 
> 	mov	rax, 0x2000004		; write system call
> 	mov	rdi, 1				; stdout
> 	mov	rsi, in_char
> 	mov	rdx, 2				; the second byte is to apply the carriage return
> expected in the string
> 	syscall
> 
> 	; exit system call
> 	mov	rax, 0x2000001		; exit system call
>        xor     rdi, rdi
> 	syscall
> }
> Again, both assembly language examples were taken from Wikipedia. I am
> no asm expert, I assure you, and with the lack of material available
> on assembly language these days... it's quite hard to learn it. I
> thank you for taking your time to read this proposal and have a nice
> day!
> -- 
> Signed,
> Ethin D. Probst
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