[LLVMdev] How to reduce the footprint of MDNodes? (About the comment you made at BOF LTO)

[Eric Christopher]

On Mon, Nov 11, 2013 at 11:29 PM, Chris Lattner <clattner at apple.com> wrote:
> Hi Manman (and llvmdev),
>
> I filed these two bugs to track the ideas that I was cooking:
>
> http://llvm.org/bugs/show_bug.cgi?id=17891
> http://llvm.org/bugs/show_bug.cgi?id=17892
>
> TL;DR: I'm saying we should go from:
>
>         !14 = metadata !{i32 786445, metadata !1, metadata !10, metadata !"y", i32 3, i64 32, i64 32, i64 32, i32 0, metadata !13}
> to:
>         !14 = metadata !"v12,14,y,3,0,32,32,32"(metadata !1, metadata !13)
>
> I think that this is along the lines of what you're thinking of, but doesn't require doing specific optimizations for constant values (since most of those would be encoded into strings instead of showing up as operands).
>
> This is a pretty big project, but I think the payoff would be a huge constant factor improvement in memory use.  We should probably also use a similar approach for profile info.
>

We can take discussion of specific format into the bugs, but a more
compact encoding is definitely a good thing. Thanks for filing the
bugs to keep track.

-eric

> -Chris
>
>
> On Nov 11, 2013, at 4:09 PM, Manman Ren <mren at apple.com> wrote:
>
>>
>> Hi Chris,
>>
>> I missed the BOF LTO session and Bob mentioned to me that you had a comment about how to reduce the footprint of MDNodes.
>
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