v0.51.0 - 2025-08-13

Final deprecations before Wasmi 1.0.

Changed

• Redesign the stack limits Config API. #1631
  • Deprecated the StackLimits type and Config::set_stack_limits method.
  • Deprecated the Config::cached_stacks method.
  • Added Config::set_{max_recursion_depth,min_stack_height,max_stack_height} methods.

v0.50.0 - 2025-08-11

This is supposedly the final release before Wasmi 1.0.0.

Added

• This version ships with an entirely new Wasm bytecode to Wasmi bytecode translator.
  • The new translator is ~5-10% faster than the old one.
  • Fuel-metering is no longer an afterthought and thus comes nearly for free.
  • The new codebase is much simpler to maintain and reason about.
  • Wasmi bytecode generated by the new translator shows similar performance as the old one.
  • The new translator provides a lot more information to Wasmi's optimizer
    which allows for new optimizations in upcoming Wasmi releases.
  • PRs: #1512 #1618
• Add lowerings for xor instructions when used in comparisons.
  • This reduced the number of Wasmi bytecode instructions by a whopping 20
    which might have positive effects on execution performance due to decreased cache
    pressure.
  • PRs: #1625

Changed

• Removed Wasmi bytecode instructions that are no longer generated by the new translator.
  • This also reduces the number of Wasmi bytecode instructions by 8 which
    might have positive effects on execution performance due to decreased cache
    pressure.
  • PRs: #1623 #1624

Internal

• Remove some Wasmi dependencies.
  • Namely, smallvec, multi-stash and arrayvec.
  • PRs: #1620 #1626

v0.49.1 - 2025-08-10

Fixes

• Fix negated f{32,64}.cmp+select op-code fusion. #1612

v0.49.0 - 2025-08-07

This version prepares Wasmi for its 1.0 release.

Changed

• Deprecate wasmi::core module re-export. #1605
  • Public facing definitions are now re-exported from wasmi's
    crate root which users should use instead.
• Improve Wasmi's Wasmtime API mirror:
  • Make ExternRef non-nullable and introduce new nullable Ref type. #1603
    • Wasmtime uses Option<ExternRef> instead which is very similar.
    • Ref<ExternRef> can be converted to Option<ExternRef> using the val method.
  • Remove FuncRef type in favor of Ref<Func> #1604
    • Wasmtime uses Option<Func> instead which is very similar.
    • Ref<Func> can be converted to Option<Func> using the val method.
  • Deprecate InstancePre and Linker::instantiate #1602
    • Enable fuel metering and set fuel to zero before instantiation
      in order to prevent running a Wasm module's start function upon
      instantiation.
  • Deprecate LinkerBuilder type. #1601
    • Use Linker or Instance::new instead.

Internal

• Refactor and clean-up Wasmi's .wast test facilities.
  • #1591 #1586 #1585 #1581 #1579 #1592
• Add .wast tests or convert unit translation tests to .wast.
  • #1569 #1575 #1580

v0.48.0 - 2025-07-21

Added

• Added Wasm reinterpret operators to wasmi_core::wasm API.

Changed

• Marked Module::new_streaming[_unchecked] API deprecated. #1540
  • Reason for the deprecation:
    • The streaming Wasm module creation is not a great fit for Wasmi's target usage.
    • No users are known that depend on this functionality - please inform us if you do!
    • Streaming Wasm module creating has a performance overhead when not needed.
• Changed CompilationMode default to CompilationMode::LazyTranslation. #1530
  • With this default Wasm is still validated eagerly but tranlated to Wasmi IR lazily.
    This gives the best of both worlds: fast startup times while avoiding partial validation.
• Update Wasmtime dependencies to v34. #1563

Fixed

• Fixed a bug that f{32,64}.copysign with immediate rhs operands won't bump fuel. #1539
• Fixed incorrect optimization application for i64.mul_wide_s. #1545 #1546
• Fixed an integer-overflow that could happen when reading or writing memory. #1554

Internal

• Optimize ControlFrame memory footprint slightly. #1534
• Slightly optimize fuse_nez and fuse_eqz routines. #1559
• Simplified lots of FuncTranslator logic. E.g. #1542 #1550 #1552
• Add some new Wasmi specific .wast test cases. #1561 #1562
• Prepare for new Wasmi translator implementation.
  • #1532 #1537 #1541 #1553 #1558 #1560

v0.47.0 - 2025-05-30

Changed

• Remove the downcast-rs dependency from Wasmi crates. #1517
• Bump the minimum supported Rust version (MSRV) to Rust 1.86. #1518
  • This change was necessitated by the removal of downcast-rs.

Internal

• Lower select instructions more aggressively. #1526
  • This significantly reduced the number of different select instruction
    variants and thus might have positive effects on Wasmi's execution performance.

v0.46.0 - 2025-05-08

Changed

• Store<T>::new no longer requires T: 'static. #1507
  • The T: 'static requirement was introduced in v0.45.0 in #1449.
• Improve host function call performance. #1506

Internal

• Updated dependencies. #1509

v0.45.0 - 2025-05-06

Added

• Added support for Wasm function call resumption after running out of fuel. #1498
  • This feature is very useful when using Wasmi inside a scheduler that works with
    Wasmi's fuel metering to provide amount of compute units to different Wasm execution
    threads for example.
• Added missing wasmi_core::simd API functions for relaxed-simd. #1447
• Added implementations for Rust's Error trait for all wasmi error types on no_std. #1462

Changed

• Avoid performing duplicate type and validation checks in Linker::instantiate. #1476
• Updated wasm-tools dependencies to v228. #1463
• Removed most of wasmi_core::TypedVal's API. #1457
  • The newer wasmi_core::wasm API is to be preferred and provides the same functionality.

Fixed

• Fixed a bug that Wasmi did not make wasmparser's parser aware of enabled Wasm features. #1502
  • Making wasmparser aware of the enabled Wasm features allows it to detect malformed Wasm
    binaries during parsing.

Internal

• Make Wasmi's executor non-generic over the Store's T. #1449
• Changes to Wasmi's IR:
  • Removed all conditional return instructions. #1486
    • This allows Wasmi to apply its powerful cmp+branch fusion in more places.
  • Remove most of the bulk-memory (and bulk-table) instruction variants. #1489
    • Wasmi still has optimized variants for the most common cases.
  • Add new logical-comparator instructions. #1494
    • This further enhances Wasmi's powerful cmp+branch instruction fusion.
  • Add negated f{32,64}.{lt,le} instructions. #1496
    • This allows Wasmi to apply its cmp+nez fusion for f{32,64}.{le,lt} instructions as well.
  • Re-design Wasmi's select instructions. #1497
    • This allows to use Wasmi's powerful cmp op-code fusion for select instructions.
• Moved many wasmi internals into wasmi_core:
  • Add FuncType #1458
  • Add Fuel, Memory, Table, Global, ResourceLimiter #1464
  • Replace uses in wasmi with wasmi_core definitions. #1460

v0.44.1 - 2025-05-04

Fixed

• Fixed a bug with executing SIMD store_lane instructions. #1450

v0.44.0 - 2023-03-29

Added

• Add support for the Wasm relaxed-simd proposal. #1443
  • All relaxed-simd operators behave deterministically on all platforms supported by Wasmi.
  • Users have to enable the simd crate feature in order to use relaxed-simd capabilities.
  • Note that enabling the simd crate feature may regress Wasm execution and memory consumption
    performance.

Changed

• Wasmi's CLI now prints multiple results on a new line each. #1438
  • With this change Wasmi's CLI and Wasmtime's CLI have the same behavior.