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From: bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: transpiling to low level C
Date: Tue, 17 Dec 2024 12:04:29 +0000
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On 16/12/2024 21:23, Lawrence D'Oliveiro wrote:
> On Sun, 15 Dec 2024 17:53:30 -0600, BGB wrote:
> 
>> As an IL, even C is a little overkill, unless turned into a restricted
>> subset ...
> 
> Why not use WASM as your IL?

Have you tried it? I mean, directly generating WASM from a compiler 
front-end, not just using somebody else's tool to do so.

WASM is a stack-based language, but one that supposedly doesn't even 
have branching, although there is a 'br' statement, with some restrictions.

Information about it is quite elusive; it took me 5 minutes to even get 
examples of what it looks like (and I've seen it before).

C can apparently compile to WASM via Clang, so I tried this program:

  void F(void) {
     int i=0;
     while (i<10000) ++i;
  }

which compiled to 128 lines of WASM (technically, some form of 'WAT', as 
WASM is a binary format). The 60 lines correspondoing to F are shown 
below, and below that, is my own stack IL code.

So, what do you with your WASM/WAT program once generated? I've no idea, 
except that WASM is inextricably typed up with with browsers and with 
JavaScript, in which I have no interest.

With C, you run a compiler; with ASM, an assembler; these formats are 
well understood.

You can appreciate that it can be easier to devise your own format and 
your own tools that you understand 100%.




--------------------------------------
F:                                      # @F
	.functype	F () -> ()
	.local  	i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, 
i32, i32
# %bb.0:
	global.get	__stack_pointer
	local.set	0
	i32.const	16
	local.set	1
	local.get	0
	local.get	1
	i32.sub
	local.set	2
	i32.const	0
	local.set	3
	local.get	2
	local.get	3
	i32.store	12
..LBB0_1:                                # =>This Inner Loop Header: Depth=1
	block   	
	loop    	                                # label1:
	local.get	2
	i32.load	12
	local.set	4
	i32.const	10000
	local.set	5
	local.get	4
	local.set	6
	local.get	5
	local.set	7
	local.get	6
	local.get	7
	i32.lt_s
	local.set	8
	i32.const	1
	local.set	9
	local.get	8
	local.get	9
	i32.and
	local.set	10
	local.get	10
	i32.eqz
	br_if   	1                               # 1: down to label0
# %bb.2:                                #   in Loop: Header=BB0_1 Depth=1
	local.get	2
	i32.load	12
	local.set	11
	i32.const	1
	local.set	12
	local.get	11
	local.get	12
	i32.add
	local.set	13
	local.get	2
	local.get	13
	i32.store	12
	br      	0                               # 0: up to label1
..LBB0_3:
	end_loop
	end_block                               # label0:
	return
	end_function

-----------------------------

proc F::
            local    i32       i.1
     load     i32       0
     store    i32       i.1
     jump               #2
#4:
     load     u64       &i.1
     incrto   i32 /1
#2:
     load     i32       i.1
     load     i32       10000
     jumplt   i32       #4
#3:
#1:
     retproc
endproc