2002637 - (ragnarok) Remove asm.js code

Status: NEW

(Core :: JavaScript: WebAssembly, task, P3)

Description

[Ryan Hunt [:rhunt]]

If we are able to unship asm.js in bug 2002635, then we will want to start removing asm.js code.

The asm.js compiler is also known as OdinMonkey, and so this will be the long-foretold Ragnarök.

Comment 1

[Yury Delendik (:yury)]

Attachment: WIP: Bug 2002637 - Remove asm.js compilation infrastructure from SpiderMonkey

This commit completely removes asm.js compilation support from SpiderMonkey,
keeping only minimal API compatibility stubs.

Core asm.js Removal:

• Remove entire asm.js compiler implementation (AsmJS.cpp/h)
• Remove AsmJS.cpp from build system

JIT Compiler Infrastructure:

• Remove MAsmJSLoadHeap, MAsmJSStoreHeap, MAsmJSMemoryAccess MIR classes
• Remove asm.js heap access operations from MIROps.yaml and LIROps.yaml
• Remove architecture-specific lowering and codegen for asm.js operations
  across arm, arm64, x86-shared, mips-shared, riscv64, loong64, wasm32
• Remove AlignmentMaskAnalysis asm.js-specific optimization
• Remove asm.js code paths from MacroAssembler, CodeGenerator, WarpOracle

Parser & Frontend:

• Remove useAsmOrInsideUseAsm() methods and all related checks
• Remove FunctionBox::functionNode field (was for asm.js error messages)
• Remove hasAsmJS() methods from Stencil classes
• Simplify constant folding and parse tree optimization (always enabled)
• Remove special asm.js handling in FunctionEmitter

WebAssembly Compilation:

• Remove callSiteLineNums from FuncCompileInput (asm.js call site tracking)
• Remove readCallSiteLineOrBytecode(), replace with readBytecodeOffset()
• Remove isAsmJS parameters from various wasm functions
• Remove asm.js-specific memory limits and checks
• Clean up wasm metadata to remove asm.js flags

API & Configuration:

• Deprecate AsmJSOption enum (all methods return DisabledByNoWasmCompiler)
• Keep ContextOptions::asmJS() and setAsmJS() as no-ops for compatibility
• Add deprecation comments explaining API compatibility
• Remove javascript.options.asmjs preference
• Remove enableAsmJS from JS shell
• Remove throwOnAsmJSValidationFailure option
• Remove asm.js-related error messages and use counter tracking

Memory & Debugging:

• Remove objectsMallocHeapElementsAsmJS memory metric
• Update memory report descriptions from "wasm/asm.js" to "wasm"
• Remove updateObservesAsmJSOnDebuggees() debugger hook
• Remove allowUnobservedAsmJS debugger option
• Clean up asm.js references in frame iteration

Testing:

• Remove gdb test-asmjs.cpp
• Remove profiler test_asm.js
• Update asm.js jit-tests to verify compilation is disabled
• Remove debugger tests for asm.js-specific features

Array Buffers & Functions:

• Remove isAsmJSMalloced() and related buffer tracking
• Remove FunctionFlags::IsAsmJSNative and related function classification
• Simplify JSFunction by removing asm.js module tracking
• Remove asm.js-specific array buffer restrictions

Documentation:

• Update comments to remove asm.js references
• Fix misleading comments about "asm.js native" functions (actually wasm)
• Add deprecation notices to remaining API stubs

Co-Authored-By: Claude Sonnet 4.5 <[e-mail]>

Comment 2

[Ryan Hunt [:rhunt]]

asm.js is now disabled in release. The current nightly is Fx150, so let's wait until Fx152 before we land this. It starts on April 20th [1].

[1] https://whattrainisitnow.com/release/?version=152