[llvm-dev] RFC: Adding a string table to the bitcode format

Rui Ueyama via llvm-dev llvm-dev at lists.llvm.org
Tue Apr 4 15:39:16 PDT 2017

On Tue, Apr 4, 2017 at 2:35 PM, Rafael EspĂ­ndola via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> > It might do, keeping in mind that reading pretty much every existing
> object
> > file format already requires scanning for string lengths. Certainly
> > something to try and evaluate, at least.
> In lld strlen does show up in the profile. I haven't benchmarked it
> recently enough to remember exactly how much.

It used to take substantial share of the total execution time (IIRC ~10%),
but since we read only global symbol names, that isn't taking that much
time now.

The string table builder code currently supports tail merging. On ELF
> at least that is a very modest size saving. If the size is written as
> a prefix to the string, that doesn't work. If the size is stored in
> the reference (like a stringef) we would be able to merge any
> substring (not sure if it is profitable).
> Cheers,
> Rafael
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