[lld] r195289 - [PECOFF] Do not check if library is already added.

[Mikael Lyngvig]

I think it sounds great!  It sounds as if Darwin and Windows does things
pretty much the same way.

I seem to recall that the linker I worked on actually did it the slow way.
 And back then, in 199x, there were absolutely no problems with speed of
the linker's resolution algorithm, so I don't think you need to worry about
doing it the slow way initially.  Most likely, you'll never need to worry
about doing it the fast way.


-- Mikael


2013/11/23 Rui Ueyama <ruiu at google.com>

> Thanks. I don't know if it's the same, but it looks like it's pretty
> similar. So the ideas to support that (non-Unix) semantics are the same as
> Nick's.
>
> 1. Implement a new Resolver behavior for Darwin/Windows. The behavior
> would be like this: Make Resolver to add all symbols from archive files to
> the symbol table as it processes new files, constructing a gigantic symbol
> table that contains all the symbols that is already resolved or *could* be
> resolved in a file that Resolver has seen. For a new object file, Resolver
> looks up the symbol table for each undefined symbol in an object file, and
> if it can be resolved in an (unparsed) archive file, parse the archive
> file, and add the symbols from the file to the symbol table.
>
> 2. Create a group for all library files and add it at the end of the input
> graph, as Nick suggested in that thread.
>
> So, (2) would be a low-impact change because it won't need any change to
> the core linker. However it would be slow because it needs to iterate over
> and over on the same library files until all undefined symbols are
> resolved. (1) would be faster because the iteration would be replaced by a
> single hash table lookup, but it'd be a high-impact change.
>
>
>
> On Fri, Nov 22, 2013 at 2:38 PM, Shankar Easwaran <shankare at codeaurora.org
> > wrote:
>
>> On 11/22/2013 4:19 PM, Rui Ueyama wrote:
>>
>>> On Fri, Nov 22, 2013 at 2:14 PM, Shankar Easwaran
>>> <shankare at codeaurora.org>wrote:
>>>
>>>  If its doing that, it might be following the Darwin model. The Darwin
>>>> model picks up all the object files and puts all the libraries that it
>>>> wants to link inside a Group(Snipped from a discussion earlier with
>>>> Nick).
>>>>
>>>>  Which thread?
>>>
>> http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-September/065365.html
>>
>> Thanks
>>
>> Shankar Easwaran
>>
>
>
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