[llvm-dev] [cfe-dev] [RFC] Embedding Bitcode in Object Files

Sergei Larin via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 4 14:18:44 PST 2016


   I would like to echo Rafael's comments.

My general understanding is that given an object file with embedded IR I should be able to reproduce the same object.
Everything else should be "supporting" that objective... which might include relevant flags and transformations leading _to_ this IR and _from_ this IR to the given object code.

Does my understanding matches your overall goal?



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> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Rafael
> EspĂ­ndola via llvm-dev
> Sent: Thursday, February 04, 2016 4:01 PM
> To: Steven Wu
> Cc: LLVM Developers Mailing List; cfe-dev
> Subject: Re: [llvm-dev] [cfe-dev] [RFC] Embedding Bitcode in Object Files
> On 3 February 2016 at 14:01, Steven Wu via llvm-dev <llvm-
> dev at lists.llvm.org> wrote:
> > Hi Peter
> >
> > It is not currently related because we started the implementation
> > before Thin-LTO gets proposed in the community but our "__LLVM,
> > __bitcode" section is pretty much the same as ".llvmbc" section. Note
> > ".llvmbc" doesn't really follow the section naming convention for
> > MachO objects. I am hoping to unify them during the upstream of the
> implementation.
> That would be my main request. Seems like a nice feature, but we should
> have one implementation of it :-)
> BTW, can you explain a bit why you need things like "-O0" recorded? In case
> you want to go from bitcode back to object file one file at a time (no LTO)? Is
> that orthogonal? That is, should the command line be included in .bc files
> too? What is the command line option that is included, the -cc1 or the driver
> one?
> There was some discussion on the past about which options get run in clang if
> given -flto. For example, it seems likely that a more conservative inlining pass
> would be a good thing to not remove opportunities for the link time inlining.
> What would happen with "-flto -fembed-bitcode"? Would the bitcode be the
> same as with just -flto and the object file less optimized?
> Cheers,
> Rafael
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