[LLVMdev] Target data question

[Kenneth Uildriks]

>> Anyway, my present plan of attack is to have a "-defaulttarget" option
>> with "none", "host", or a target string.  If -defaulttarget is not
>> specified, the behavior of "opt" will be the same as it is presently.
>> The defaulttarget will be overridden by the Module's target data if it
>> has some.  "none" means that no TargetData pass will be added unless
>> the Module supplies target data.  "host" uses the running host's
>> TargetData as the default.
>>
>> What do y'all think?
>
> I think it's more intuitive to have command-line information override
> Module information. That's how llc works, for example.
>
> Also, is the argument to -defaulttarget a triple, an architecture name,
> or a targetdata string? If it's a triple, it'd be nice to be consistent
> with llc and call it -mtriple=. For an architecture name, -march=.
> If it's a targetdata string, perhaps -targetdata= would be a good name.
>
> (As an aside, I wouldn't object to having llc's options renamed to
> remove the leading 'm', as that seems to have been intended to follow
> GCC's targeting options, and they aren't the same.)
>
> Dan
>
>

The argument to -default-data-layout is a targetdata string.
-no-default-data-layout means that no TargetData pass is added unless
the module supplies a target data string.

llvm-gcc always inserts targetdata.  I'm wondering if the code it
generates somehow depends on the assumption that 'opt' is taking its
target data into account.  As in, some of it uses absolute offsets and
some of it uses pointer-indexing that gets affected by the targetdata.
 Anyway, it seemed safer to take the module's targetdata if it was
built  with targetdata included