[PATCH] Pass -mglobal-merge as a module flag metadata.

[Eric Christopher]

On Mon, Mar 16, 2015 at 8:27 AM Akira Hatanaka <ahatanak at gmail.com> wrote:

> On Fri, Mar 13, 2015 at 4:09 PM, Eric Christopher <echristo at gmail.com>
> wrote:
>
>> No, you probably haven't. I was seeing it as clang doing to lto link of
>> the module together and then codegen based on that (which means it would
>> have the options), but...
>>
>> That said, I think the general problem is more specific. I.e. how do you
>> specify -msse3 as part of the default code generation flags when you do lto?
>>
>>
> In LTOCodeGenerator.cpp, SubtargetFeatures::getDefaultSubtargetFeatures is
> called to get the default subtarget features and the string is passed to
> TargetCreateTargetMachine.
>
> Is that what you are asking about?
>

Yes, but that code doesn't work in the abstract. It only works on darwin
because it has hard coded values. The features there are only based on the
triple so saying that you want to pass in a default of -msse3 to your code
generator doesn't work unless you a) hard code a cpu into
LTOCodeGenerator.cpp or, b) hard code it into the triple (x86_64h anyone?).

-eric


>
>
>> The C++ interface has addAttr (which is painful in that it requires, as
>> you say, every linker to understand llvm's command line interface), but
>> this is also pretty painful:
>>
>>   const void *compile(size_t *length,
>>                       bool disableOpt,
>>                       bool disableInline,
>>                       bool disableGVNLoadPRE,
>>                       bool disableVectorization,
>>                       std::string &errMsg);
>>
>> because, you know, all optimizations, inlining, gvnloadpre, and
>> vectorization are all anyone care about :)
>>
>> Realize this has dovetailed into "let's solve the general problem" but I
>> am curious. The gold plugin's methods aren't much better.
>>
>> Or am I missing something?
>>
>> -eric
>>
>>
>> http://reviews.llvm.org/D7968
>>
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