Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Rollup of 4 pull requests #90276

Closed
wants to merge 8 commits into from

Conversation

matthiaskrgr
Copy link
Member

Successful merges:

Failed merges:

r? @ghost
@rustbot modify labels: rollup

Create a similar rollup

jblazquez and others added 8 commits October 11, 2021 12:09
This change adds a new compiler flag that can help reduce the size of
ELF binaries that contain many functions.

By default, when enabling function sections (which is the default for most
targets), the LLVM backend will generate different section names for each
function. For example, a function "func" would generate a section called
".text.func". Normally this is fine because the linker will merge all those
sections into a single one in the binary. However, starting with LLVM 12
(llvm/llvm-project@ee5d1a0), the backend will
also generate unique section names for exception handling, resulting in
thousands of ".gcc_except_table.*" sections ending up in the final binary
because some linkers don't currently merge or strip these EH sections.
This can bloat the ELF headers and string table significantly in
binaries that contain many functions.

The new option is analogous to Clang's -fno-unique-section-names, and
instructs LLVM to generate the same ".text" and ".gcc_except_table"
section for each function, resulting in smaller object files and
potentially a smaller final binary.
And add a rustdoc-gui test confirming various header sizes.
…, r=jyn514,camelid,notriddle

Fix clippy lints in librustdoc

I ran clippy on librustdoc and simply fixed the lints. :)

r? `@notriddle`
Add -Z no-unique-section-names to reduce ELF header bloat.

This change adds a new compiler flag that can help reduce the size of ELF binaries that contain many functions.

By default, when enabling function sections (which is the default for most targets), the LLVM backend will generate different section names for each function. For example, a function `func` would generate a section called `.text.func`. Normally this is fine because the linker will merge all those sections into a single one in the binary. However, starting with [LLVM 12](llvm/llvm-project@ee5d1a04), the backend will also generate unique section names for exception handling, resulting in thousands of `.gcc_except_table.*` sections ending up in the final binary because some linkers like LLD don't currently merge or strip these EH sections (see discussion [here](https://reviews.llvm.org/D83655)). This can bloat the ELF headers and string table significantly in binaries that contain many functions.

The new option is analogous to Clang's `-fno-unique-section-names`, and instructs LLVM to generate the same `.text` and `.gcc_except_table` section for each function, resulting in a smaller final binary.

The motivation to add this new option was because we have a binary that ended up with so many ELF sections (over 65,000) that it broke some existing ELF tools, which couldn't handle so many sections.

Here's our old binary:

```
$ readelf --sections old.elf | head -1
There are 71746 section headers, starting at offset 0x2a246508:

$ readelf --sections old.elf | grep shstrtab
  [71742] .shstrtab      STRTAB          0000000000000000 2977204c ad44bb 00      0   0  1
```

That's an 11MB+ string table. Here's the new binary using this option:

```
$ readelf --sections new.elf | head -1
There are 43 section headers, starting at offset 0x29143ca8:

$ readelf --sections new.elf | grep shstrtab
  [40] .shstrtab         STRTAB          0000000000000000 29143acc 0001db 00      0   0  1
```

The whole binary size went down by over 20MB, which is quite significant.
…omez

Fix documentation header sizes

And add a rustdoc-gui test confirming various header sizes.

Split off from rust-lang#90156. This fixes a regression in rust-lang#89506 where the heading level of titles within Markdown was too high (h2) for docblocks under structs, unions, and enum impls.

r? ``@camelid``

Demo: https://jacob.hoffman-andrews.com/rust/fix-header-sizes/std/string/struct.String.html#impl-Add%3C%26%27_%20str%3E
Stable: https://doc.rust-lang.org/stable/std/string/struct.String.html#impl-Add%3C%26%27_%20str%3E
Beta: https://doc.rust-lang.org/beta/std/string/struct.String.html#impl-Add%3C%26%27_%20str%3E
…=lnicola

⬆️ rust-analyzer

r? ~~`@ghose~~` sorry, `@ghost`
@rustbot rustbot added the rollup A PR which is a rollup label Oct 25, 2021
@matthiaskrgr
Copy link
Member Author

@bors r+ p=4 rollup=never

@bors
Copy link
Contributor

bors commented Oct 25, 2021

📌 Commit 57655d9 has been approved by matthiaskrgr

@bors bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Oct 25, 2021
@bors
Copy link
Contributor

bors commented Oct 25, 2021

⌛ Testing commit 57655d9 with merge e3278758c43b4d9d62c5989182c5a76c30407d8a...

@rust-log-analyzer
Copy link
Collaborator

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)
.........  (49/49)


header-size... FAILED
[ERROR] (line 27) Error: Evaluation failed: expected `16px` for key `font-size` for selector `#impl > h3.code-header`, found `17.6px`: for command `assert-css: ("#impl > h3.code-header", {"font-size": "16px"}) // 1em`



command did not execute successfully: "/node-v14.4.0-linux-x64/bin/node" "/checkout/src/tools/rustdoc-gui/tester.js" "--jobs" "16" "--doc-folder" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/rustdoc-gui/doc" "--tests-folder" "/checkout/src/test/rustdoc-gui"


Build completed unsuccessfully in 0:00:16

@rust-log-analyzer
Copy link
Collaborator

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)
.......... (50/50)


header-size... FAILED
[ERROR] (line 27) Error: Evaluation failed: expected `16px` for key `font-size` for selector `#impl > h3.code-header`, found `17.6px`: for command `assert-css: ("#impl > h3.code-header", {"font-size": "16px"}) // 1em`



command did not execute successfully: "/node-v14.4.0-linux-x64/bin/node" "/checkout/src/tools/rustdoc-gui/tester.js" "--jobs" "16" "--doc-folder" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/rustdoc-gui/doc" "--tests-folder" "/checkout/src/test/rustdoc-gui"


Build completed unsuccessfully in 0:00:17

@matthiaskrgr matthiaskrgr deleted the rollup-il37sxg branch November 20, 2021 15:04
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
rollup A PR which is a rollup S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

8 participants