Integrate Wasmi IR 3.0 into `wasmi` #1655

Robbepop · 2025-09-10T08:21:48Z

Wasmi IR 3.0 definitions: #1650

Closed Issues

Closes #1598
Closes #1632
Closes #1639
Closes #1516
Closes #1485
Closes #1433
Closes #1324

Potential optimizations:

Use same ip in execution handlers as in op-decode. (🟢 -11% fibonacci/iter)
Integrate instance stack in CallStack into frames. (easy)
Return TrapCode::OutOfSystemMemory in Stack operations where necessary.
Redesign portable-dispatch to avoid state copy and improve performance. (medium)
Properly use extra-checks for technically-infallible conditional panics. (easy)
Use byte-offsets for Slot type to avoid mul-by-8 during execution. (easy)
Use extern "sysv64" ABI for execution handlers on Windows. (medium)
Use variable sized cell load/stores for 32-bit operands: Implement variable sized VM registers #1671
Make Wasmi IR Instance related instead of Module related: Move Wasm function details into the Store #1492

Development Notes

Interpretation loop must be panic-free for tail calls to be properly generated without the become keyword.
- This means that we have to wrap host function calls with ::core::panic::catch_unwind and convert potential panics into flags signalling bad state to the interpreter.
- Furthermore, we need to establish a way to signal to the interpretation loop that we are in an error state (e.g. encountered a bug) and have to exit the interpretation loop safely before resolving the bug, e.g. via panicking.

ToDo

Fix known bugs:

Fix bugs with branch operator execution.
- Likely, the branch offsets are incorrect.
Fix integer-overflow in Wasmi translator.
Fix execution issue with recursive operation sequences.
Fix bug in stripping start and end of copy_span values in translator.
Fix bugs leading to incorrect reverse_complement result.
Fix bugs leading to incorrect regex_redux result.

Implement Functionality

Preliminary Benchmarks

Preliminary benchmarks of this WIP state pre-optimization shows interesting results:

`execute/fibonacci/iter`

Crate Features	PR	`main`	%
	578us	705us	🟢 -18%
`compact`	840us	-	🔴 +19%
`trampolines`	1.92ms	-	🔴 x2.7
`compact+trampolines`	1.8ms	-	🔴 x2.6

`execute/fibonacci/rec`

Crate Features	PR	`main`	%
	2.84ms	3.77ms	🟢 -24%
`compact`	4.10ms	-	🔴 +8%
`trampolines`	5.32ms	-	🔴 +41%
`compact+trampolines`	6.3ms	-	🔴 +67%

`execute/fibonacci/tail`

Crate Features	PR	`main`	%
	481us	777us	🟢 -38%
`compact`	728us	-	🟢 -7%
`trampolines`	1.04ms	-	🔴 +34%
`compact+trampolines`	1.26ms	-	🔴 +62%

`execute/tiny_keccak`

Crate Features	PR	`main`	%
	114us	193ms	🟢 -41%
`compact`	183us	-	🟢 -4%
`trampolines`	421ms	-	🔴 x2.18
`compact+trampolines`	360ms	-	🔴 x1.87

Benchmarks Conclusion

The tail-call-based direct-dispatch outperforms main significantly.
The tail-call-based indirect-dispatch is somewhat on par with main.
Both trampoline-based dispatches are wastly outperformed by main.
- Note: the reason partly is really bad codegen due to unnecessary register copies which should be fixable.

* improve debug_assert failure message * fix field ordering of TableSet operations * add #[inline(always)] to decode impl Benchmarks show significant performance improvements. * add #[inline(always)] to TryFrom<u16> for OpCode * improve code formatting in match * add trivial {Read,Write}As impls for UntypedVal * add From<Memory> for u32 impl * apply rustfmt

codecov · 2025-11-12T10:44:25Z

Codecov Report

❌ Patch coverage is 83.47768% with 248 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.48%. Comparing base (099194d) to head (89a95ff).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/wasmi/src/engine/translator/comparator.rs	40.66%	89 Missing ⚠️
crates/wasmi/src/engine/executor/handler/state.rs	88.42%	33 Missing ⚠️
crates/wasmi/src/engine/executor/handler/func.rs	73.04%	31 Missing ⚠️
crates/wasmi/src/engine/executor/handler/exec.rs	93.81%	30 Missing ⚠️
crates/wasmi/src/engine/executor/mod.rs	77.14%	16 Missing ⚠️
.../wasmi/src/engine/executor/handler/dispatch/mod.rs	77.19%	13 Missing ⚠️
crates/wasmi/src/engine/executor/handler/eval.rs	81.25%	12 Missing ⚠️
...c/engine/executor/handler/dispatch/backend/loop.rs	77.27%	5 Missing ⚠️
crates/wasmi/src/engine/translator/func/encoder.rs	54.54%	5 Missing ⚠️
crates/wasmi/src/engine/translator/func/visit.rs	69.23%	4 Missing ⚠️
... and 7 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1655      +/-   ##
==========================================
- Coverage   70.61%   62.48%   -8.14%     
==========================================
  Files         180      164      -16     
  Lines       15338    13200    -2138     
==========================================
- Hits        10831     8248    -2583     
- Misses       4507     4952     +445

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yet unused

Those are more stable under debug conditions and also add more checks for improved debugging.

This is incorrect as demonstrated by the following example: - `(1 & 2) == 0` - `(1 != 0) && (2 != 0) == 1`

- compact -> indirect-dispatch - trampolines -> portable-dispatch

This fixes some stack overflow issues when running tests with portable-dispatch disabled. Ideally, we were able to fix those instances without requiring codegen-units=1.

Robbepop marked this pull request as draft September 10, 2025 08:21

Robbepop mentioned this pull request Sep 11, 2025

Update wasmi_ir2 crate #1656

Merged

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch 7 times, most recently from 41aad7c to bb8b966 Compare September 18, 2025 10:11

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch 2 times, most recently from 12a19d4 to 64f420e Compare September 19, 2025 14:54

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch 2 times, most recently from 48242ca to 4d2d316 Compare October 4, 2025 10:55

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch from 7bfb899 to c32c7c7 Compare October 24, 2025 13:52

Robbepop mentioned this pull request Oct 27, 2025

Redesign Store and StoreInner internal error handling #1679

Merged

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch 4 times, most recently from d9ec934 to c68956c Compare November 2, 2025 23:40

Robbepop mentioned this pull request Nov 8, 2025

Forward misc. integration changes from #1655 #1688

Merged

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch 2 times, most recently from 12257b9 to 7a87159 Compare November 10, 2025 12:43

Robbepop mentioned this pull request Nov 12, 2025

Add host call regression test cases wasmi-labs/wasmi-tests#10

Merged

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch from d206f23 to ffbd7c8 Compare November 13, 2025 09:16

Robbepop added 4 commits November 14, 2025 11:33

update wasmi_ir2 constructor usage

5d4c97a

add Stack::drop_n method

3d27335

fix bug in Wasm loop translation

8ef6b98

make pin_label_if_unpinned encode the currently staged operator

abb1260

Robbepop added 16 commits November 14, 2025 11:34

add ValueStack::grow_if_needed method

3fe078f

yet unused

make use of ValueStack::grow_if_needed

cd7b743

fix bug after using ValueStack::grow_if_needed

a377fca

relaxed debug_assert and add comment

090290d

disable SIMD specific Wast test for now

c47e75f

fix bug in ValueStack::prepare_host_frame

3c9bef1

add default features to wasmi_wast

bdc2354

simplify memory_bytes utility method

2459cfe

use trampolines and extra-checks features in the fuzzer

4b704b4

Those are more stable under debug conditions and also add more checks for improved debugging.

fix, refactor and clean-up ValueStack::replace

04fe981

disable simd and relaxed-simd in the fuzzer for now

0d9e520

remove short-circuiting from wasmi_i32_and

3082129

This is incorrect as demonstrated by the following example: - `(1 & 2) == 0` - `(1 != 0) && (2 != 0) == 1`

mirror i32.and evaluation fix for i64.and

b4e005a

rename new crate features

2648bc6

- compact -> indirect-dispatch - trampolines -> portable-dispatch

add codegen-units=1 to release profile

1dd6342

This fixes some stack overflow issues when running tests with portable-dispatch disabled. Ideally, we were able to fix those instances without requiring codegen-units=1.

simplify the Done type

75ab76b

Robbepop force-pushed the rf-integrate-wasmi-ir-3.0 branch from 23af6c2 to 75ab76b Compare November 14, 2025 10:35

Robbepop added 13 commits November 14, 2025 12:01

fix some incorrect execution handler identifiers

ad02823

fix for_each_op expansion

401d5d8

add stubs for all unimplemented simd operators

79c28e7

apply rustfmt

e10ad47

use for_each_op to implement op_code_to_handler

da42d5f

move control macros to utils

1bd060a

move WasmFuncCall and HostFuncCall into func submodule

28e2a1e

move dispatch.rs -> dispatch/mod.rs

3d644e4

move execute_until_done into its respective backend

9829410

move dispatch macro into its respective backend

f061182

move NextState into its respective backend

f9772a2

move control_break into its respective backend

a019d59

move Done type into its respective backend

89a95ff

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Closed Issues

Potential optimizations:

Development Notes

ToDo

Fix known bugs:

Implement Functionality

Preliminary Benchmarks

execute/fibonacci/iter

execute/fibonacci/rec

execute/fibonacci/tail

execute/tiny_keccak

Benchmarks Conclusion

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Integrate Wasmi IR 3.0 into `wasmi` #1655

Integrate Wasmi IR 3.0 into `wasmi` #1655

Robbepop commented Sep 10, 2025 •

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`execute/fibonacci/iter`

`execute/fibonacci/rec`

`execute/fibonacci/tail`

`execute/tiny_keccak`

codecov bot commented Nov 12, 2025 •

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