[LLVMdev] LLVM Language Reference Strictness

reed kotler rkotler at mips.com
Fri Oct 21 13:14:08 PDT 2011

On 10/21/2011 09:28 AM, Owen Anderson wrote:
> Reed,
> On Oct 20, 2011, at 9:47 AM, Reed Kotler wrote:
>> I would like to see the many adhoc parsers in LLVM get replaced by ones
>> generated from grammars.
> FYI, this is very unlikely to happen.  The parsers in LLVM /were/ 
> historically generated from grammars (bison, as I recall), and those 
> implementations were removed in favor of hand-written implementations 
> both because the latter were significantly easier to maintain, and 
> because they were much better suited to offer reasonable diagnostics. 
>  Any plan to reverse that decisions is likely to meet a lot of resistance.
> --Owen
I'm not planing to use Bison or YACC or Antlr. I stated that in my email.

Don't assume that I'm an idiot although it's a possibility. I've been 
doing compilers off and on for 35 years now. Ideas in computer science 
are like fashion in clothes; if you wait around long enough then 
everything comes back into fashion. All the web and flow of how people 
do things in compilers has already come and gone many times.

Right now it's pretty easy to crash tablegen if you have table errors, 
for example. That is not exactly giving reasonable diagnostics.

It's very hard to write hand written parsers even for simple languages 
and not have lots of problems.
This is compounded over time as things change.

Hopefully what I do will meet with acceptance. I'll take that chance.


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