Move to Rust 1.92. Bump MSRV to 1.84.

.github/scripts/ci-common.sh

@@ -10,7 +10,6 @@ cargo_toml=$project_root/Cargo.toml
 dummyvm_toml=$project_root/docs/dummyvm/Cargo.toml
 
 # Pin certain deps for our MSRV
-cargo update -p [email protected] --precise 0.5.5 # This can be removed once we move to Rust 1.81 or newer
 cargo update -p [email protected] --precise 0.5.5 # This requires Rust edition 2024
 
 # Repeat a command for all the features. Requires the command as one argument (with double quotes)

.github/workflows/micro-bm.yml

@@ -69,7 +69,7 @@ jobs:
         with:
           repository: mmtk/ci-perf-kit
           token: ${{ secrets.GITHUB_TOKEN }}
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           submodules: true
       # Use rust-toolchain in the trunk (it doesnt matter much - if the toolchains defined in the trunk and the branch are different, we cant run anyway)

.github/workflows/perf-baseline.yml

@@ -42,7 +42,7 @@ jobs:
         with:
           token: ${{ secrets.CI_ACCESS_TOKEN }}
           repository: mmtk/ci-perf-kit
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           submodules: true
       # setup
@@ -94,7 +94,7 @@ jobs:
         with:
           token: ${{ secrets.CI_ACCESS_TOKEN }}
           repository: mmtk/ci-perf-kit
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           submodules: true
       # setup

.github/workflows/perf-compare-ci.yml

@@ -112,7 +112,7 @@ jobs:
             with:
               repository: mmtk/ci-perf-kit
               token: ${{ secrets.CI_ACCESS_TOKEN }}
-              ref: "0.8.4"
+              ref: "0.8.5"
               path: ci-perf-kit
               submodules: true
           # setup
@@ -223,7 +223,7 @@ jobs:
               with:
                 repository: mmtk/ci-perf-kit
                 token: ${{ secrets.CI_ACCESS_TOKEN }}
-                ref: "0.8.4"
+                ref: "0.8.5"
                 path: ci-perf-kit
                 submodules: true
             # setup

.github/workflows/perf-regression-ci.yml

@@ -45,7 +45,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: mmtk/ci-perf-kit
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           token: ${{ secrets.CI_ACCESS_TOKEN }}
           submodules: true
@@ -142,7 +142,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: mmtk/ci-perf-kit
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           submodules: true
       # download canary build
@@ -233,7 +233,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: mmtk/ci-perf-kit
-          ref: "0.8.4"
+          ref: "0.8.5"
           path: ci-perf-kit
           token: ${{ secrets.CI_ACCESS_TOKEN }}
           submodules: true

Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/mmtk/mmtk-core"
 readme = "README.md"
 categories = ["memory-management"]
 keywords = ["gc", "garbage", "collection", "garbage-collection", "allocation"]
-rust-version = "1.74.1"
+rust-version = "1.84"
 build = "build.rs"
 
 [lib]
@@ -59,24 +59,9 @@ paste = "1.0.8"
 rand = "0.9.0"
 rand_chacha = "0.9.0"
 criterion = "0.5"
-# Note: `half` v2.5.0 started to require Rust 1.81.
-# `criterion` transitively depends on `half` via the dependency chain:
-#     criterion -> ciborium -> ciborium_ll -> half
-# The MSRV of `ciborium` v0.2.2 is declared as 1.58, and is declared to depend on `half` v2.2.
-# Ciborium should either bump its MSRV or select a version of `half` that satisfies its current MSRV.
-# We lock the version of `half` to 2.4.1 to workaround this.
-# TODO: When we bump MSRV to 1.84 or above, we can rely on Cargo's MSRV-aware dependency resolver and remove such workarounds.
-half = "=2.4.1"
 
 [build-dependencies]
 built = { version = "0.7.7", features = ["git2"] }
-# Note: Some components in ICU4X started to require Rust 1.81 since some versions, such as `litemap` v0.7.5.
-# The `built` crate depends on ICU4X via the dependency chain:
-#     built -> git2 -> url -> idna -> idna_adapter --(default)--------> crates from the ICU4X projects
-#                                                  --(alternatively)--> `unicode-rs`
-# But we don't need ICU4X (or even `url`) because we only use `git2` to get the Git commit hash.
-# We move away from ICU4X completely following the instruction in https://docs.rs/crate/idna_adapter/1.2.0
-idna_adapter = "=1.1.0"
 
 [lints.clippy]
 # Allow this. Clippy suggests we should use Sft, Mmtk, rather than SFT and MMTK.
@@ -88,10 +73,9 @@ idna_adapter = "=1.1.0"
 # to me - considering it will break our API and all the efforts for all the developers to make the change, it may
 # not worth it.
 upper_case_acronyms = "allow"
-# Temporarily allow this -- 9 July 2025. Clippy suggests that we should always inline format args if possible.
-# We see pushbacks on this lint in Rust 1.67, and the lint was downgraded to pedantic in 1.67.1. It was upgraded
-# again in Rust 1.88. We temporarily disable this lint and see the reaction from the community.
-# If there is no pushback for this lint in a few momnths' time, we should remove the following line and migrate the codebase.
+# Allow this -- 9 July 2025. Clippy suggests that we should always inline format args if possible.
+# This lint was upgraded to 'style' in Rust 1.67, and then was downgraded to pedantic in 1.67.1.
+# It was upgraded again in Rust 1.88, and downgraded again in Rust 1.89. We disable this lint to avoid warnings in affected versions.
 # See https://github.com/mmtk/mmtk-core/issues/1334.
 uninlined_format_args = "allow"
 

rust-toolchain

@@ -1 +1 @@
-1.83.0
+1.92.0

src/policy/sft_map.rs

@@ -141,7 +141,9 @@ impl SFTRefStorage {
         let val = self.0.load(Ordering::Acquire);
         // Provenance-related APIs were stabilized in Rust 1.84.
         // Rust 1.91 introduced the warn-by-default lint `integer_to_ptr_transmutes`.
-        // Since our MSRV is still 1.74.1, we can't fix it until bumping MSRV.
+        // However, pointer provenance API only works for ptr-sized intergers, and
+        // here we are transmuting from a double-word sized integer to a fat pointer.
+        // We still need to use transmute here.
         #[allow(unknown_lints)]
         #[allow(integer_to_ptr_transmutes)]
         unsafe {

src/util/alloc/allocator.rs

@@ -172,13 +172,9 @@ pub fn align_allocation_inner<VM: VMBinding>(
     }
 
     // May require an alignment
-    let region_isize = region.as_usize() as isize;
     let mask = (alignment - 1) as isize; // fromIntSignExtend
     let neg_off: isize = -(offset as isize); // fromIntSignExtend
-
-    // TODO: Consider using neg_off.wrapping_sub_unsigned(region.as_usize()), and we can remove region_isize.
-    // This requires Rust 1.66.0+.
-    let delta = neg_off.wrapping_sub(region_isize) & mask; // Use wrapping_sub to avoid overflow
+    let delta = neg_off.wrapping_sub_unsigned(region.as_usize()) & mask; // Use wrapping_sub to avoid overflow
 
     if fillalignmentgap && (VM::ALIGNMENT_VALUE != 0) {
         fill_alignment_gap::<VM>(region, region + delta);

src/util/erase_vm.rs

@@ -17,17 +17,13 @@ macro_rules! define_erased_vm_mut_ref {
         pub struct $new_type<'a>(usize, PhantomData<&'a ()>);
         impl<'a> $new_type<'a> {
             pub fn new<VM: VMBinding>(r: &'a mut $orig_type) -> Self {
-                let worker_as_usize: usize = unsafe { std::mem::transmute(r) };
+                let worker_as_usize: usize = (r as *mut $orig_type).expose_provenance();
                 Self(worker_as_usize, PhantomData)
             }
             pub fn into_mut<VM: VMBinding>(self) -> &'a mut $orig_type {
-                // Provenance-related APIs were stabilized in Rust 1.84.
-                // Rust 1.91 introduced the warn-by-default lint `integer_to_ptr_transmutes`.
-                // Since our MSRV is still 1.74.1, we can't fix it until bumping MSRV.
-                #[allow(unknown_lints)]
-                #[allow(integer_to_ptr_transmutes)]
                 unsafe {
-                    std::mem::transmute(self.0)
+                    &mut *(std::ptr::with_exposed_provenance(self.0) as *const $orig_type
+                        as *mut $orig_type)
                 }
             }
         }