[beta] Backports for compiler-builtins by tgross35 · Pull Request #162820 · rust-lang/rust

tgross35 · 2026-09-15T19:02:22Z

Backport #160594 and part of #162816. The compiler-builtins portion includes rust-lang/compiler-builtins#1317 and two other trivial commits that avoid conflicts.

Closes: #162259

rustbot · 2026-09-15T19:02:27Z

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tgross35 · 2026-09-15T19:05:26Z

@bors try jobs=test-various,test-armhf-gnu,dist-arm-linux-gnueabi,dist-armhf-linux,dist-armv7-linux

[beta] Backports for compiler-builtins try-job: test-various try-job: test-armhf-gnu try-job: dist-arm-linux-gnueabi try-job: dist-armhf-linux try-job: dist-armv7-linux

[beta] Backports for compiler-builtins try-job: test-various try-job: dist-arm-linux-gnueabi try-job: dist-armhf-linux try-job: dist-armv7-linux

rust-bors · 2026-09-15T21:27:23Z

💔 Test for 3abffe9 failed: CI. Failed jobs:

try - dist-arm-linux-gnueabi (web logs, enhanced plaintext logs)
try - dist-armhf-linux (web logs, enhanced plaintext logs)

thejpster · 2026-09-16T16:06:05Z

+        }
+    }
+}
+>>>>>>> a7f33f3f8c9 (c-b: Add `aeabi_u(read|write)(4|8)` intrinsics.)


This seems wrong?

View changes since the review

Oof, thanks

thejpster · 2026-09-16T16:08:18Z

The failures there are in ARMv6 targets (dist-arm-linux-gnueabi and dist-armhf-linux).

##[group]Building stage1 library artifacts (stage1:x86_64-unknown-linux-gnu -> stage1:arm-unknown-linux-gnueabihf)
    Updating crates.io index
 Downloading crates ...
  Downloaded addr2line v0.27.1
  Downloaded cc v1.2.0
  Downloaded memchr v2.8.3
  Downloaded miniz_oxide v0.9.1
  Downloaded hashbrown v0.17.1
  Downloaded gimli v0.34.0
  Downloaded object v0.39.1
  Downloaded libc v0.2.189
   Compiling shlex v1.3.0
   Compiling core v0.0.0 (/checkout/library/core)
   Compiling libc v0.2.189
   Compiling object v0.39.1
   Compiling cc v1.2.0
   Compiling std v0.0.0 (/checkout/library/std)
   Compiling test v0.0.0 (/checkout/library/test)
   Compiling compiler_builtins v0.1.160 (/checkout/library/compiler-builtins/compiler-builtins)
   Compiling profiler_builtins v0.0.0 (/checkout/library/profiler_builtins)
warning: profiler_builtins@0.0.0: /checkout/src/llvm-project/compiler-rt/lib/profile/GCDAProfiling.c:567:1: warning: destructor priorities from 0 to 100 are reserved for the implementation
warning: profiler_builtins@0.0.0:  static void llvm_writeout_and_clear(void) {
warning: profiler_builtins@0.0.0:  ^~~~~~
   Compiling rustc-std-workspace-core v1.99.0 (/checkout/library/rustc-std-workspace-core)
   Compiling alloc v0.0.0 (/checkout/library/alloc)
error: <inline asm>:22:1: invalid instruction, any one of the following would fix this:
bx lr
^

note: <inline asm>:22:1: instruction requires: armv4t
bx lr
^

note: <inline asm>:22:1: instruction requires: thumb
bx lr
^

error: invalid instruction, any one of the following would fix this:
   |
note: instantiated into assembly here
  --> <inline asm>:22:1
   |
22 | bx lr
   | ^

note: instruction requires: armv4t
   |
note: instantiated into assembly here
  --> <inline asm>:22:1
   |
22 | bx lr
   | ^

note: instruction requires: thumb
   |
note: instantiated into assembly here
  --> <inline asm>:22:1
   |
22 | bx lr
   | ^

error: could not compile `compiler_builtins` (lib) due to 1 previous error

But those targets have armv4t and thumb features, and the function compiles fine in Godbolt on that target. It's like the code is compiling for ARMv4? I note the other asm examples don't use BX LR to return - they use PUSH { LR } ... POP { PC }, which does work on very old Arm architectures.

tgross35 · 2026-09-16T16:32:46Z

For lack of knowing where else to look, I guess @rust-lang/bootstrap do you happen to know if something changed with settings for these jobs between beta and main? Considering the code builds on main as well as the current beta, but seems to be rejected in CI.

Kobzol · 2026-09-16T17:54:47Z

I don't recall anything that might affect this, and the error doesn't ring a bell. Though cc was updated semi-recently, I think.

[beta] Backports for compiler-builtins try-job: test-various try-job: dist-arm-linux-gnueabi try-job: dist-armhf-linux try-job: dist-armv7-linux

tgross35 · 2026-09-16T18:55:45Z

@bors try jobs=test-various,dist-arm-linux-gnueabi,dist-armhf-linux,dist-armv7-linux

[beta] Backports for compiler-builtins try-job: test-various try-job: dist-arm-linux-gnueabi try-job: dist-armhf-linux try-job: dist-armv7-linux

rust-bors · 2026-09-16T21:09:14Z

💔 Test for 28822f9 failed: CI. Failed jobs:

try - dist-arm-linux-gnueabi (web logs, enhanced plaintext logs)
try - dist-armhf-linux (web logs, enhanced plaintext logs)

tgross35 · 2026-09-16T21:34:26Z

Replicated locally without a full dist build using CARGO_TARGET_ARM_UNKNOWN_LINUX_GNUEABIHF_LINKER="clang --target=arm-unknown-linux-gnueabihf" CC_arm_unknown_linux_gnueabihf="clang --target=arm-unknown-linux-gnueabihf" ./x build std --target arm-unknown-linux-gnueabihf (using clang since I'm not on Linux)

tgross35 · 2026-09-16T22:22:25Z

Smaller yet: RUSTC_BOOTSTRAP=1 cargo +beta build --target=arm-unknown-linux-gnueabihf --profile=dist -p alloc --manifest-path /Volumes/CaseSensitive/rust/library/sysroot/Cargo.toml. The --profile=dist seems to be load bearing

tgross35 · 2026-09-16T22:36:39Z

Reproduced, fails on <=beta but works on nightly https://rust.godbolt.org/z/osb3WW4xW. Asking more on #t-compiler/help > Valid `bx lr` rejected on arm

tgross35 · 2026-09-17T01:37:02Z

@bors try jobs=test-various,dist-arm-linux-gnueabi,dist-armhf-linux,dist-armv7-linux

[beta] Backports for compiler-builtins try-job: test-various try-job: dist-arm-linux-gnueabi try-job: dist-armhf-linux try-job: dist-armv7-linux

rust-bors · 2026-09-17T03:53:48Z

☀️ Try build successful (CI)
Build commit: 7243266 (7243266afca61ac4a2c5981cb99b00d4d3e5c813)
Base parent: fba1b05 (fba1b05a7bd8bdc73080edd02f672cef44648267)

(cherry picked from commit 37aaf5c)

This is a rather old config, added in c924aed0b9ac ("Fix Armv8-M Baseline compilation"). `thumb_1` is somewhat misleading, since targets with `thumb2` also support basic `thumb` instructions. Rename it to be more clear about what this is actually checking. The config is not currently used but may be in the future. (cherry picked from commit 5c59263)

We still match on target name because we can't always rely on config from the unstable `arm_target_feature`. However, we can still assert that things match up when running in the compiler-builtins CI. This is disabled for now because it fails on three thumb targets: * thumbv4t-none-eabi * thumbv5te-none-eabi * thumbv6-none-eabi This will be resolved in a future commit. Checking for the verbose build is a good indicator that we are in our CI, rather than any other that might set the `CI` env. (cherry picked from commit 9e5d248)

Fixes: rust-lang#162259 (cherry picked from commit a7f33f3)

(cherry picked from commit 192ea4f)

tgross35 · 2026-09-17T10:44:54Z

~~Relnotes specifically for the backport of #160594, #t-compiler/backports > #160594: beta-nominated @ 💬~~ scratch that, they're opened on that PR now

cuviper · 2026-09-19T01:10:48Z

I've added this to #162987.

rustbot assigned Mark-Simulacrum Sep 15, 2026

rustbot added A-compiler-builtins Area: compiler-builtins (https://github.com/rust-lang/compiler-builtins) S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Sep 15, 2026

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rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 15, 2026

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tgross35 mentioned this pull request Sep 15, 2026

compiler-builtins subtree update #162816

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tgross35 mentioned this pull request Sep 16, 2026

Undefined symbol errors on __aeabi_uread* and __aeabi_uwrite* functions with opt-level = "z" and build-std #162259

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thejpster reviewed Sep 16, 2026

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tgross35 force-pushed the beta-compiler-builtins branch from aa588bb to f4b83bb Compare September 16, 2026 18:33

rustbot added the T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) label Sep 16, 2026

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tgross35 force-pushed the beta-compiler-builtins branch from fbd1b44 to 9ea0e4f Compare September 16, 2026 18:55

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tgross35 mentioned this pull request Sep 17, 2026

attach global target features to module-level assembly #160594

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rustbot added the A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. label Sep 17, 2026

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folkertdev and others added 5 commits September 17, 2026 03:58

forward global target features to module-level assembly

0aec535

(cherry picked from commit 37aaf5c)

c-b: Add aeabi_u(read|write)(4|8) intrinsics.

5d21053

Fixes: rust-lang#162259 (cherry picked from commit a7f33f3)

build: Fix thumb_1 cfg to include all "thumb but not thumbv2" targets.

c174b56

(cherry picked from commit 192ea4f)

tgross35 force-pushed the beta-compiler-builtins branch from f7f5d59 to c174b56 Compare September 17, 2026 03:58

tgross35 added this to the 1.99.0 milestone Sep 17, 2026

tgross35 added the relnotes Marks issues that should be documented in the release notes of the next release. label Sep 17, 2026

rustbot mentioned this pull request Sep 17, 2026

Tracking issue for release notes of #162820: [beta] Backports for compiler-builtins #162891

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tgross35 removed the relnotes Marks issues that should be documented in the release notes of the next release. label Sep 17, 2026

tgross35 mentioned this pull request Sep 19, 2026

[beta] backports #162987

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tgross35 closed this Sep 19, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Sep 19, 2026

tgross35 deleted the beta-compiler-builtins branch September 19, 2026 01:25

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