Update to LLVM 21 #143684

nikic · 2025-07-09T12:41:26Z

Timeline: LLVM 21.1.0 is scheduled to release on Aug 26th. Rust 1.90 branches on Aug 1st and releases September 18.

Depends on:

r? @ghost

rustbot · 2025-07-09T12:41:31Z

These commits modify compiler targets.
(See the Target Tier Policy.)

nikic · 2025-07-09T12:46:44Z

@bors2 try @rust-timer queue

Update to LLVM 21 r? `@ghost`

rust-bors · 2025-07-09T12:46:48Z

⌛ Trying commit ebb63b9 with merge c3e645b…

To cancel the try build, run the command @bors2 try cancel.

rust-bors · 2025-07-09T14:22:01Z

💔 Test failed

CI ❌

nikic · 2025-07-09T14:30:42Z

Noooo, a crash while profiling with the bolt instrumentation.

    process didn't exit successfully: `/tmp/tmp-multistage/opt-artifacts/rustc-perf/target/debug/rustc-fake --crate-name regex_automata --edition=2021 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/regex-automata-0.4.9/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no --cfg 'feature="alloc"' --cfg 'feature="dfa-onepass"' --cfg 'feature="dfa-search"' --cfg 'feature="hybrid"' --cfg 'feature="meta"' --cfg 'feature="nfa"' --cfg 'feature="nfa-backtrack"' --cfg 'feature="nfa-pikevm"' --cfg 'feature="nfa-thompson"' --cfg 'feature="perf"' --cfg 'feature="perf-inline"' --cfg 'feature="perf-literal"' --cfg 'feature="perf-literal-multisubstring"' --cfg 'feature="perf-literal-substring"' --cfg 'feature="std"' --cfg 'feature="syntax"' --cfg 'feature="unicode"' --cfg 'feature="unicode-age"' --cfg 'feature="unicode-bool"' --cfg 'feature="unicode-case"' --cfg 'feature="unicode-gencat"' --cfg 'feature="unicode-perl"' --cfg 'feature="unicode-script"' --cfg 'feature="unicode-segment"' --cfg 'feature="unicode-word-boundary"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "default", "dfa", "dfa-build", "dfa-onepass", "dfa-search", "hybrid", "internal-instrument", "internal-instrument-pikevm", "logging", "meta", "nfa", "nfa-backtrack", "nfa-pikevm", "nfa-thompson", "perf", "perf-inline", "perf-literal", "perf-literal-multisubstring", "perf-literal-substring", "std", "syntax", "unicode", "unicode-age", "unicode-bool", "unicode-case", "unicode-gencat", "unicode-perl", "unicode-script", "unicode-segment", "unicode-word-boundary"))' -C metadata=29004f3d2c23a6dc -C extra-filename=-acaa9aabb4aa769d --out-dir /tmp/.tmpSoAMdr/target/release/deps -C linker=clang -C strip=debuginfo -L dependency=/tmp/.tmpSoAMdr/target/release/deps --extern aho_corasick=/tmp/.tmpSoAMdr/target/release/deps/libaho_corasick-f3f82c9a60cf08f9.rmeta --extern memchr=/tmp/.tmpSoAMdr/target/release/deps/libmemchr-e5f42c55eae6f759.rmeta --extern regex_syntax=/tmp/.tmpSoAMdr/target/release/deps/libregex_syntax-7bce46b340cd2bfa.rmeta --cap-lints allow` (signal: 11, SIGSEGV: invalid memory reference)

Kobzol · 2025-07-09T15:31:03Z

Noooo, a crash while profiling with the bolt instrumentation.

    process didn't exit successfully: `/tmp/tmp-multistage/opt-artifacts/rustc-perf/target/debug/rustc-fake --crate-name regex_automata --edition=2021 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/regex-automata-0.4.9/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no --cfg 'feature="alloc"' --cfg 'feature="dfa-onepass"' --cfg 'feature="dfa-search"' --cfg 'feature="hybrid"' --cfg 'feature="meta"' --cfg 'feature="nfa"' --cfg 'feature="nfa-backtrack"' --cfg 'feature="nfa-pikevm"' --cfg 'feature="nfa-thompson"' --cfg 'feature="perf"' --cfg 'feature="perf-inline"' --cfg 'feature="perf-literal"' --cfg 'feature="perf-literal-multisubstring"' --cfg 'feature="perf-literal-substring"' --cfg 'feature="std"' --cfg 'feature="syntax"' --cfg 'feature="unicode"' --cfg 'feature="unicode-age"' --cfg 'feature="unicode-bool"' --cfg 'feature="unicode-case"' --cfg 'feature="unicode-gencat"' --cfg 'feature="unicode-perl"' --cfg 'feature="unicode-script"' --cfg 'feature="unicode-segment"' --cfg 'feature="unicode-word-boundary"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "default", "dfa", "dfa-build", "dfa-onepass", "dfa-search", "hybrid", "internal-instrument", "internal-instrument-pikevm", "logging", "meta", "nfa", "nfa-backtrack", "nfa-pikevm", "nfa-thompson", "perf", "perf-inline", "perf-literal", "perf-literal-multisubstring", "perf-literal-substring", "std", "syntax", "unicode", "unicode-age", "unicode-bool", "unicode-case", "unicode-gencat", "unicode-perl", "unicode-script", "unicode-segment", "unicode-word-boundary"))' -C metadata=29004f3d2c23a6dc -C extra-filename=-acaa9aabb4aa769d --out-dir /tmp/.tmpSoAMdr/target/release/deps -C linker=clang -C strip=debuginfo -L dependency=/tmp/.tmpSoAMdr/target/release/deps --extern aho_corasick=/tmp/.tmpSoAMdr/target/release/deps/libaho_corasick-f3f82c9a60cf08f9.rmeta --extern memchr=/tmp/.tmpSoAMdr/target/release/deps/libmemchr-e5f42c55eae6f759.rmeta --extern regex_syntax=/tmp/.tmpSoAMdr/target/release/deps/libregex_syntax-7bce46b340cd2bfa.rmeta --cap-lints allow` (signal: 11, SIGSEGV: invalid memory reference)

Oh no, the day has finally come 😆

nikic · 2025-07-09T16:44:32Z

llvm/llvm-project#147781 for pr-check-1 assertion failure.

bors · 2025-07-10T05:52:36Z

☔ The latest upstream changes (presumably #143703) made this pull request unmergeable. Please resolve the merge conflicts.

nikic · 2025-07-10T10:33:49Z

llvm/llvm-project#147935 for armhf-gnu test failure.

nikic · 2025-07-10T12:56:26Z

llvm/llvm-project#139443 for musl build failure.

nikic · 2025-07-11T10:54:39Z

llvm/llvm-project#148207 for x86_64-gnu-nopt assertion failure.

nikic · 2025-07-14T12:17:33Z

llvm/llvm-project#148607 for the brand new x86_64-gnu-miri build failure...

bors · 2025-07-14T13:25:21Z

☔ The latest upstream changes (presumably #143873) made this pull request unmergeable. Please resolve the merge conflicts.

nikic · 2025-07-15T16:44:46Z

@bors2 try

I was unable to reproduce the bolt issue locally. Fingers crossed that I just hit a bad commit or something.

Update to LLVM 21 Depends on: * [x] llvm/llvm-project#147781 * [x] llvm/llvm-project#147935 * [x] llvm/llvm-project#139443 * [x] llvm/llvm-project#148207 * [x] llvm/llvm-project#148607 r? `@ghost`

rust-bors · 2025-07-15T16:44:51Z

⌛ Trying commit b0b9a3c with merge cd80bb6…

To cancel the try build, run the command @bors2 try cancel.

rust-bors · 2025-08-05T17:33:28Z

☀️ Try build successful (CI)
Build commit: 9e5b077 (9e5b07782fd4829ce008a42c5187742f758e38a4, parent: 0f353363965ebf05e0757f7679c800b39c51a07e)

nikic · 2025-08-05T19:02:00Z

Yay, that worked. I've switched the compiler-rt build for the host compiler to use the runtimes configuration, where compiler-rt gets built by the just-built clang. The host GCC is not able to compile it anymore on aarch64. We could try updating it, but as the project build for compiler-rt is deprecated anyway, this seems preferable.

cuviper · 2025-08-05T19:22:31Z

@bors r+

bors · 2025-08-05T19:22:34Z

📌 Commit e6c0e63 has been approved by cuviper

It is now in the queue for this repository.

tgross35 · 2025-08-05T19:45:22Z

@bors p=5

(giving the same priority as rollups so this can iterate quicker if needed)

Update to LLVM 21 Timeline: LLVM 21.1.0 is scheduled to release on Aug 26th. Rust 1.90 branches on Aug 1st and releases September 18. Depends on: * [x] llvm/llvm-project#147781 * [x] llvm/llvm-project#147935 * [x] llvm/llvm-project#139443 * [x] llvm/llvm-project#148207 * [x] llvm/llvm-project#148607 * [x] llvm/llvm-project#149046 * [x] llvm/llvm-project#149097 * [x] #144116 r? `@ghost`

bors · 2025-08-05T22:01:24Z

⌛ Testing commit e6c0e63 with merge 54bb377...

bors · 2025-08-06T04:01:24Z

💥 Test timed out

rust-log-analyzer · 2025-08-06T04:03:31Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

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

tgross35 · 2025-08-06T04:35:21Z

@bors retry

bors · 2025-08-06T04:36:57Z

⌛ Testing commit e6c0e63 with merge dc0bae1...

bors · 2025-08-06T08:34:50Z

☀️ Test successful - checks-actions
Approved by: cuviper
Pushing dc0bae1 to master...

github-actions · 2025-08-06T08:37:46Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing ec7c026 (parent) -> dc0bae1 (this PR)

Test differences

Show 26 test diffs

Stage 2

[codegen] tests/codegen-llvm/enum/enum-discriminant-eq.rs#LLVM20: ignore (only executed when the pointer width is 64bit) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 20) (J0)
[codegen] tests/codegen-llvm/enum/enum-discriminant-eq.rs#LLVM21: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> ignore (only executed when the pointer width is 64bit) (J0)
[assembly] tests/assembly-llvm/nvptx-safe-naming.rs#LLVM20: ignore (only executed when the architecture is nvptx64) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 20) (J1)
[assembly] tests/assembly-llvm/nvptx-safe-naming.rs#LLVM21: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> ignore (only executed when the architecture is nvptx64) (J1)
[assembly] tests/assembly-llvm/riscv-soft-abi-with-float-features.rs#LLVM-PRE-20: ignore (ignored when the LLVM version (20.1.8) is newer than majorversion 19) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 19) (J1)
[assembly] tests/assembly-llvm/sanitizer/kcfi/emit-arity-indicator.rs#x86_64: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> pass (J1)
[assembly] tests/assembly-llvm/x86_64-bigint-helpers.rs#llvm-pre-20: ignore (ignored when the LLVM version (20.1.8) is newer than majorversion 19) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 19) (J1)
[codegen] tests/codegen-llvm/integer-cmp.rs#llvm-pre-20: ignore (ignored when the LLVM version (20.1.8) is newer than majorversion 19) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 19) (J1)
[codegen] tests/codegen-llvm/option-niche-eq.rs#LLVM21: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> pass (J1)
[codegen] tests/codegen-llvm/sanitizer/kcfi/add-kcfi-arity-flag.rs#x86_64: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> pass (J1)
[codegen] tests/codegen-llvm/try_question_mark_nop.rs#NINETEEN: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J1)
[assembly] tests/assembly-llvm/x86_64-cmp.rs#LLVM-PRE-20-DEBUG: ignore (ignored when the LLVM version (20.1.8) is newer than majorversion 19) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 19) (J2)
[assembly] tests/assembly-llvm/x86_64-cmp.rs#LLVM-PRE-20-OPTIM: ignore (ignored when the LLVM version (20.1.8) is newer than majorversion 19) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 19) (J2)
[codegen] tests/codegen-llvm/issues/issue-101082.rs#x86-64-v3: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> pass (J2)
[ui] tests/ui/abi/sparcv8plus-llvm19.rs#sparc: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J3)
[ui] tests/ui/abi/sparcv8plus-llvm19.rs#sparc_cpu_v9: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J3)
[ui] tests/ui/abi/sparcv8plus-llvm19.rs#sparc_cpu_v9_feature_v8plus: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J3)
[ui] tests/ui/abi/sparcv8plus-llvm19.rs#sparc_feature_v8plus: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J3)
[ui] tests/ui/abi/sparcv8plus-llvm19.rs#sparcv8plus: ignore (ignored when the actual LLVM major version is 20, but the test only targets major version 19) -> ignore (ignored when the actual LLVM major version is 21, but the test only targets major version 19) (J3)
[ui] tests/ui/sanitizer/kcfi-arity-requires-llvm-21-0-0.rs: pass -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 20) (J4)
[ui] tests/ui/sanitizer/kcfi-arity-requires-llvm-21-0-0.rs: ignore (ignored on targets without kernel CFI sanitizer) -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 20) (J5)
[run-make] tests/run-make/compressed-debuginfo-zstd: pass -> ignore (ignored if LLVM wasn't build with zstd for ELF section compression (we want LLVM/LLD to be built with zstd support)) (J6)
[codegen] tests/codegen-llvm/enum/enum-discriminant-eq.rs#LLVM20: pass -> ignore (ignored when the LLVM version (21.1.0) is newer than majorversion 20) (J7)
[codegen] tests/codegen-llvm/enum/enum-discriminant-eq.rs#LLVM21: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> pass (J7)
[codegen] tests/codegen-llvm/issues/issue-101082.rs#x86-64-v3: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> ignore (only executed when the architecture is x86_64) (J8)

Additionally, 1 doctest diff were found. These are ignored, as they are noisy.

Job group index

J0: arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1
J1: aarch64-apple, aarch64-gnu, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-apple-1, x86_64-gnu, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
J2: test-various, x86_64-apple-1, x86_64-gnu, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
J3: aarch64-apple, aarch64-gnu, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-apple-2, x86_64-gnu, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
J4: aarch64-gnu, x86_64-gnu, x86_64-gnu-nopt, x86_64-gnu-stable
J5: aarch64-apple, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-apple-2, x86_64-mingw-1, x86_64-msvc-1
J6: x86_64-gnu-nopt
J7: aarch64-apple, aarch64-gnu, aarch64-msvc-1, test-various, x86_64-apple-1, x86_64-gnu, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
J8: aarch64-apple, aarch64-gnu, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard dc0bae1db725fbba8524f195f74f680995fd549e --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

aarch64-apple: 4895.5s -> 7314.9s (49.4%)
pr-check-1: 1738.0s -> 2332.5s (34.2%)
x86_64-gnu-tools: 3684.7s -> 4683.9s (27.1%)
x86_64-rust-for-linux: 3030.0s -> 3779.0s (24.7%)
armhf-gnu: 5160.6s -> 6381.6s (23.7%)
x86_64-gnu-miri: 4821.1s -> 5913.9s (22.7%)
test-various: 4946.9s -> 6037.5s (22.0%)
pr-check-2: 2793.8s -> 3358.5s (20.2%)
x86_64-gnu-stable: 7581.0s -> 9070.6s (19.6%)
arm-android: 6157.9s -> 7193.4s (16.8%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-08-06T10:44:51Z

Finished benchmarking commit (dc0bae1): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.2%, 0.9%]	5
Regressions ❌ (secondary)	1.3%	[0.4%, 1.8%]	19
Improvements ✅ (primary)	-1.3%	[-23.1%, -0.2%]	216
Improvements ✅ (secondary)	-2.7%	[-19.0%, -0.1%]	266
All ❌✅ (primary)	-1.3%	[-23.1%, 0.9%]	221

Max RSS (memory usage)

Results (primary -3.8%, secondary 1.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.4%, 0.8%]	3
Regressions ❌ (secondary)	2.8%	[0.7%, 9.2%]	18
Improvements ✅ (primary)	-4.8%	[-9.7%, -1.1%]	13
Improvements ✅ (secondary)	-3.1%	[-6.4%, -1.1%]	4
All ❌✅ (primary)	-3.8%	[-9.7%, 0.8%]	16

Cycles

Results (primary -4.6%, secondary -2.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.6%	[1.5%, 10.8%]	5
Improvements ✅ (primary)	-4.6%	[-9.4%, -1.7%]	9
Improvements ✅ (secondary)	-3.9%	[-9.9%, -1.4%]	30
All ❌✅ (primary)	-4.6%	[-9.4%, -1.7%]	9

Binary size

Results (primary -0.1%, secondary -0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.1%]	27
Regressions ❌ (secondary)	0.1%	[0.0%, 0.2%]	12
Improvements ✅ (primary)	-0.2%	[-0.4%, -0.0%]	27
Improvements ✅ (secondary)	-0.2%	[-1.0%, -0.1%]	38
All ❌✅ (primary)	-0.1%	[-0.4%, 0.1%]	54

Bootstrap: 467.149s -> 463.057s (-0.88%)
Artifact size: 377.42 MiB -> 377.38 MiB (-0.01%)

klensy · 2025-08-06T15:06:17Z

-- Not building llvm-mt because libxml2 is not available

so now missing "bin/llvm-mt". Or it unused anyway?

nikic · 2025-08-06T15:13:42Z

@klensy See

rust/src/bootstrap/src/lib.rs

Lines 60 to 75 in dc0bae1

    
           const LLVM_TOOLS: &[&str] = &[ 
        
               "llvm-cov",      // used to generate coverage report 
        
               "llvm-nm",       // used to inspect binaries; it shows symbol names, their sizes and visibility 
        
               "llvm-objcopy",  // used to transform ELFs into binary format which flashing tools consume 
        
               "llvm-objdump",  // used to disassemble programs 
        
               "llvm-profdata", // used to inspect and merge files generated by profiles 
        
               "llvm-readobj",  // used to get information from ELFs/objects that the other tools don't provide 
        
               "llvm-size",     // used to prints the size of the linker sections of a program 
        
               "llvm-strip",    // used to discard symbols from binary files to reduce their size 
        
               "llvm-ar",       // used for creating and modifying archive files 
        
               "llvm-as",       // used to convert LLVM assembly to LLVM bitcode 
        
               "llvm-dis",      // used to disassemble LLVM bitcode 
        
               "llvm-link",     // Used to link LLVM bitcode 
        
               "llc",           // used to compile LLVM bytecode 
        
               "opt",           // used to optimize LLVM bytecode 
        
           ];

for the list of distributed LLVM tools.

Kobzol · 2025-08-12T06:35:55Z

Improvements heavily outweigh regressions.

@rustbot label: +perf-regression-triaged