llvm dev - Mar 2021 - Why the binary size in trunk are smaller significantly?

Hi all,

I am working on how to reduce the size of the binary produced for coroutine with
`-g`.

In a private code bases, I find that the binary size produced in llvm-11 is 60M
while the size produced in trunk is 51M.

I tried to find the patch who made this change in git log or in phabricator by
keywords like `reduce`, 'size' or 'binary'. But I find nothing.

May I ask does anyone knows what patch makes the binary size smaller from
llvm-11 to now?

thanks,
Chuanqi
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Hi Chuanqi,

On Tue, Mar 30, 2021 at 9:47 AM chuanqi.xcq via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> In a private code bases, I find that the binary size produced in llvm-11 is
60M while the size produced in trunk is 51M.
>
> I tried to find the patch who made this change in git log or in phabricator
by keywords like `reduce`, 'size' or 'binary'. But I find
nothing.
Interesting -- which sections reduce in size between llvm-11 and
trunk? Assuming you're using ELF/DWARF binaries, `readelf -W -S` will
give you sections and sizes.

Since llvm-11 branched, there were some patches [0] that improved how
variable locations are represented in DWARF, I've seen some binaries
where that reduced file size by 10%. That would be reflected in the
.debug_loc section. There's also the constructor homing flag, passed
to clang with "-Xclang -fuse-ctor-homing", I'm not sure whether
it's
on by default in trunk. That would show a significant reduction in the
.debug_info section.

[0] https://reviews.llvm.org/rG0b5a8050ea39355a3876cc6bba9383d91e224e1f

--
Thanks,
Jeremy

The patch that did it might have been trying to solve some unrelated problem,
and this was just a side effect. Perhaps a git-bisect could help you isolate the
patch?

Thanks,
   Christopher Tetreault

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of
chuanqi.xcq via llvm-dev
Sent: Tuesday, March 30, 2021 1:47 AM
To: llvm-dev at lists.llvm.org
Subject: [EXT] [llvm-dev] Why the binary size in trunk are smaller
significantly?

Hi all,

I am working on how to reduce the size of the binary produced for coroutine with
`-g`.

In a private code bases, I find that the binary size produced in llvm-11 is 60M
while the size produced in trunk is 51M.

I tried to find the patch who made this change in git log or in phabricator by
keywords like `reduce`, 'size' or 'binary'. But I find nothing.

May I ask does anyone knows what patch makes the binary size smaller from
llvm-11 to now?

thanks,
Chuanqi
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