[LLVMdev] Linking tools (original) (raw)

Reid Kleckner rnk at google.com
Mon Jul 27 10:34:46 PDT 2015

On Mon, Jul 27, 2015 at 9:59 AM, Russell Wallace <russell.wallace at gmail.com> wrote:

On Mon, Jul 27, 2015 at 5:52 PM, Reid Kleckner <rnk at google.com> wrote:

I think your original description of the situation is accurate. llvm-link will take multiple bitcode files and spit out a big ball o' bitcode, but that's usually not sufficient for LTO, which is the main use case that we want to support.

To be clear I understand you: the reason it's usually not sufficient is because most programs use build systems that don't really provide an opportunity for such a step; they assume the compiler only needs to be told about one source file at a time right up until machine code linking time?

In practice, it's not sufficient because there are usually pre-compiled objects passed into the link step, and symbols from the bitcode are referenced from those object files. Getting the precise list of symbols that are actually referenced externally is a big part of the value of LTO. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150727/467fe6d5/attachment.html>

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