Update the minimum external LLVM to 20 #145071

cuviper · 2025-08-07T22:27:02Z

With this change, we'll have stable support for LLVM 20 and 21.
For reference, the previous increase to LLVM 19 was #139275.

cc @rust-lang/wg-llvm
r? nikic

compiler/rustc_codegen_ssa/src/traits/builder.rs

nikic · 2025-08-08T07:54:06Z

src/ci/github-actions/jobs.yml

-      IMAGE: x86_64-gnu-llvm-19
-      DOCKER_SCRIPT: x86_64-gnu-llvm3.sh
-    <<: *job-linux-4c
-


Not directly related to this PR, but does this mean we're actually running different jobs in PR CI and auto CI? PR CI runs some on aarch64, but here everything uses x86_64.

Yes, #141576 only changed the PR side. (cc @marcoieni)
There was also a zulip discussion here.

yes. That's true. If you think it would be better to use the same runner in the auto build, we can switch to aarch64 in the auto build, too 👍

tests/assembly-llvm/x86_64-cmp.rs

nikic · 2025-08-08T07:56:54Z

r=me once it's time.

rustbot · 2025-09-16T19:01:26Z

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

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

cuviper · 2025-09-16T20:43:04Z

@bors r=nikic

bors · 2025-09-16T20:43:07Z

📌 Commit 88bef49 has been approved by nikic

It is now in the queue for this repository.

Update the minimum external LLVM to 20 With this change, we'll have stable support for LLVM 20 and 21. For reference, the previous increase to LLVM 19 was rust-lang#139275. cc `@rust-lang/wg-llvm` r? nikic

Update the minimum external LLVM to 20 With this change, we'll have stable support for LLVM 20 and 21. For reference, the previous increase to LLVM 19 was rust-lang#139275. cc ``@rust-lang/wg-llvm`` r? nikic

scottmcm · 2025-09-17T05:10:45Z

compiler/rustc_codegen_ssa/src/traits/builder.rs

+        // FIXME: This implementation was designed around LLVM's ability to optimize, but `cg_llvm`
+        // overrides this to just use `@llvm.scmp`/`ucmp` since LLVM 20. This default impl should be
+        // reevaluated with respect to the remaining backends like cg_gcc, whether they might use
+        // specialized implementations as well, or continue to use a generic implementation here.


Cranelift now prefers the sub-based one too (https://github.com/bytecodealliance/wasmtime/blob/3cc0023cb60295ee15931d40b266d723f4598eba/cranelift/codegen/src/opts/spaceship.isle#L5) so I'd be tempted to just only have that here now.

But leaving it as a FIXME for this PR is probably the right choice 👍

Rollup of 14 pull requests Successful merges: - #142807 (libtest: expose --fail-fast as an unstable command-line option) - #144871 (Stabilize `btree_entry_insert` feature) - #145071 (Update the minimum external LLVM to 20) - #145181 (remove FIXME block from `has_significant_drop`, it never encounters inference variables) - #145660 (initial implementation of the darwin_objc unstable feature) - #145838 (don't apply temporary lifetime extension rules to non-extended `super let`) - #146259 (Suggest removing Box::new instead of unboxing it) - #146410 (Iterator repeat: no infinite loop for `last` and `count`) - #146460 (Add tidy readme) - #146552 (StateTransform: Do not renumber resume local.) - #146564 (Remove Rvalue::Len again.) - #146581 (Detect attempt to use var-args in closure) - #146588 (tests/run-make: Update list of statically linked musl targets) - #146631 (cg_llvm: Replace some DIBuilder wrappers with LLVM-C API bindings (part 3)) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #145071 - cuviper:min-llvm-20, r=nikic Update the minimum external LLVM to 20 With this change, we'll have stable support for LLVM 20 and 21. For reference, the previous increase to LLVM 19 was #139275. cc ```@rust-lang/wg-llvm``` r? nikic

cg_llvm: Move target machine command-line quoting from C++ to Rust When this code was introduced in #130446 and #131805, it was complicated by the need to maintain compatibility with earlier versions of LLVM. Now that LLVM 20 is the baseline (#145071), we can do all of the quoting in pure Rust code, and pass two flat strings to LLVM to be used as-is. --- In this PR, my priority has been to preserve the existing behaviour as much as possible, without worrying too much about what the behaviour *should* be. (Though I did avoid a leading space before the first argument.)

cg_llvm: Move target machine command-line quoting from C++ to Rust When this code was introduced in rust-lang/rust#130446 and rust-lang/rust#131805, it was complicated by the need to maintain compatibility with earlier versions of LLVM. Now that LLVM 20 is the baseline (rust-lang/rust#145071), we can do all of the quoting in pure Rust code, and pass two flat strings to LLVM to be used as-is. --- In this PR, my priority has been to preserve the existing behaviour as much as possible, without worrying too much about what the behaviour *should* be. (Though I did avoid a leading space before the first argument.)

Rollup of 14 pull requests Successful merges: - rust-lang/rust#142807 (libtest: expose --fail-fast as an unstable command-line option) - rust-lang/rust#144871 (Stabilize `btree_entry_insert` feature) - rust-lang/rust#145071 (Update the minimum external LLVM to 20) - rust-lang/rust#145181 (remove FIXME block from `has_significant_drop`, it never encounters inference variables) - rust-lang/rust#145660 (initial implementation of the darwin_objc unstable feature) - rust-lang/rust#145838 (don't apply temporary lifetime extension rules to non-extended `super let`) - rust-lang/rust#146259 (Suggest removing Box::new instead of unboxing it) - rust-lang/rust#146410 (Iterator repeat: no infinite loop for `last` and `count`) - rust-lang/rust#146460 (Add tidy readme) - rust-lang/rust#146552 (StateTransform: Do not renumber resume local.) - rust-lang/rust#146564 (Remove Rvalue::Len again.) - rust-lang/rust#146581 (Detect attempt to use var-args in closure) - rust-lang/rust#146588 (tests/run-make: Update list of statically linked musl targets) - rust-lang/rust#146631 (cg_llvm: Replace some DIBuilder wrappers with LLVM-C API bindings (part 3)) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned nikic Aug 7, 2025