[llvm-dev] Getting LLVM Instructions

[David Blaikie via llvm-dev]

I'm not sure that LLVM's bitcode format would natively support just a
handful of Instructions, rather than a whole llvm::Module.

If you really want just a handful of instructions, maybe text is the
way to go - it sounded like you were serializing whole functions, at
least - which could be copied/cloned/moved into a standalone
llvm::Module and serialized from there. If it's only select
instructions, then maybe text is fine? Or maybe you can summarize the
information you want from the call more succinctly than LLVM's textual
representation.

On Mon, Jul 20, 2020 at 12:00 PM Yugesh Kothari <kothariyugesh at gmail.com> wrote:
>
> Replicating what clang -emit-llvm does sound like the better way to do it.
>
> I was looking under IRPrintingPasses but couldn't find anything specific that would allow me to print out say a std::vector<llvm:: Instruction*>.
>
> What do you think would be the easiest way to do this? Can I do some hack where I can get away without writing my own llvm pass? I'm not even sure what the right question to ask is, since this is the first time I'm working with llvm.
>
> Thanks!
>
> On Mon, 20 Jul, 2020, 10:37 pm David Blaikie, <dblaikie at gmail.com> wrote:
>>
>> if you're trying to serialize LLVM IR and read it back again later -
>> yeah, probably best to use th binary searialization rather than the
>> textual. If I were doing this I'd try building something using clang
>> with -emit-llvm (that'll produce LLVM IR bitcode in the .o file) and
>> debug that to see which APIs are used to do that.
>>
>> On Mon, Jul 20, 2020 at 3:19 AM Yugesh Kothari via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> >
>> > Hi,
>> >
>> > I am working on a project where I need to get a list of llvm Functions that were called during an execution (for futher analysis).
>> > To do this I have maintained a vector<llvm:: Function*> which I print out to a .ll file at the end. However this takes a lot of time since the number of call Instructions is HUGE.
>> > I feel that the bottleneck is the conversion from llvm:: Function to std::string
>> >
>> > How can I speed this up?
>> >
>> > I don't necessarily need it in .ll format, if there is a way to dump the entire llvm::Function object as a byte stream to a .dat file and read it back as objects in a separate script, that would work too. I'm not sure how to do this (tried few things didn't work), any help would be appreciated!
>> >
>> > Thanks!
>> >
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