Strip unexpected debuginfo from libLLVM.so and librustc_driver.so when not requesting any debuginfo

[lqd]

As seen in #114175 and in this zulip discussion, there's still some small amount of debuginfo in LLVM's shared library on linux, even when not requesting it (nightly CI), coming from libstdc++.

$ readelf --debug-dump=info ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/libLLVM-16-rust-1.73.0-nightly.so | grep DW_TAG_compile_unit -A5 | grep DW_AT_comp_dir | cut -d ":" -f 2- | counts
101 counts
(  1)       39 (38.6%, 38.6%):  (indirect string, offset: 0x7): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/libsupc++
(  2)       38 (37.6%, 76.2%):  (indirect string, offset: 0x43fb2): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src/c++11
(  3)       23 (22.8%, 99.0%):  (indirect string, offset: 0x18ed8): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src/c++98
(  4)        1 ( 1.0%,100.0%):  (indirect string, offset: 0x53f04): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src

Similarly, here's librustc_driver.so when not requesting debuginfo from either rustc or the tools (nightly CI), coming e.g. from our LLVM wrapper:

$ readelf --debug-dump=info ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-e534b3a316089f5f.so | grep DW_TAG_compile_unit -A5 | grep DW_AT_comp_dir | cut -d ":" -f 2- | counts
116 counts
(  1)       34 (29.3%, 29.3%):  (indirect string, offset: 0x3c11): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/libsupc++
(  2)       32 (27.6%, 56.9%):  (indirect string, offset: 0x9753c): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src/c++11
(  3)       25 (21.6%, 78.4%):  (indirect string, offset: 0x393bd): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src/c++98
(  4)       23 (19.8%, 98.3%):  (indirect string, offset: 0x33ed3): /cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.98
(  5)        1 ( 0.9%, 99.1%):  (indirect string, offset: 0xaffff): /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8
(  6)        1 ( 0.9%,100.0%):  (indirect string, offset: 0xb604a): /tmp/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src

To reduce the size of distributed artifacts, this PR strips debuginfo from the LLVM and rustc_driver shared libraries, when:

• no debuginfo is requested when building LLVM: link-shared is true, optimize is true and release-debuginfo is false
• no debuginfo is requested when building the rustc driver:
  • debuginfo-level-rustc and debuginfo-level-tools are off.
  • when building with a stage != 0 compiler: since this is about the distributed artifacts, there's no need to do this at other stages.
• for both: on a x64 linux host and target where strip -g is available and fixes the issue (I don't know how to strip debuginfo from a .dylib on mac). The LLVM BOLTed .so, and librustc_driver.so are big there, and this will help a little. Other targets/hosts can be added in the future if we want to.

#114175 did the same thing unconditionally in opt-dist, prior to BOLTing LLVM. But this should only be used in conjunction with the other config options mentioned above, and which opt-dist doesn't know about. Therefore, it makes more sense as in bootstrap when building LLVM and rustc when applicable and no debuginfo is requested.

This shouldn't interact badly with CI caching builds and artifacts, right?

---

From the other PR, libLLVM-16-rust-1.73.0-nightly.so prior to #114141:

• master: 173.13 MiB
• stripped debuginfo: 165.12 MiB (-8 MiB, -4.6%)

libLLVM-16-rust-1.73.0-nightly.so after #114141:

• master: 121.13 MiB
• stripped debuginfo: 113.12 MiB (still -8 MiB, -6.6%)

librustc_driver.so:

• master: 118.58 MiB
• stripped debuginfo: 106.46 MiB (-12 MiB, -10.2%)

(Results are also available in this most recent perf run's artifact sizes)

[rustbot]

r? @ozkanonur

(rustbot has picked a reviewer for you, use r? to override)

[rustbot]

This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp.

[onur-ozkan]

@bors r+ rollup

[bors]

📌 Commit c98c512 has been approved by ozkanonur

It is now in the queue for this repository.

[matthiaskrgr]

@bors rollup=never

[bors]

⌛ Testing commit c98c512 with merge a7caaae...

[bors]

☀️ Test successful - checks-actions
Approved by: ozkanonur
Pushing a7caaae to master...

[rust-timer]

Finished benchmarking commit (a7caaae): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-0.2%, -0.2%]	2

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.2%	[3.2%, 3.2%]	1
Regressions ❌ (secondary)	3.1%	[3.1%, 3.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.2%	[3.2%, 3.2%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-4.1%, -2.0%]	9
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 649.049s -> 647.584s (-0.23%)