64-bit atomic load not implemented

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#4,519 opened on Feb 22, 2022 1 comment 1 reaction 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 35/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Stale
Tech stack: cpp, wasm
Domain: compilers

Research direction

Start in I64ToI32Lowering.cpp at visitLoad, where the reported assertion rejects the SAFE_HEAP_LOAD_i64_1_A operation. Reproduce the -sWASM=0 -pthread -sSAFE_HEAP debugging case and determine how the 64-bit load is handled; done means this case no longer triggers the “64-bit atomic load not implemented” assertion.

Written by the indexing model from the issue text.

Description

Trying to debug some code today with -sWASM=0 -pthread -sSAFE_HEAP, and I get

Assertion failed: (!curr->isAtomic && "64-bit atomic load not implemented"), function visitLoad, file /Users/clb/emsdk/binaryen/main/src/passes/I64ToI32Lowering.cpp, line 375.

The atomic operation comes from

 (func $SAFE_HEAP_LOAD_i64_1_A (param $0 i32) (param $1 i32) (result i64)

In this particular case I would not care even if 64-bit ops were atomic or not, so even if those were available as nonatomic, it would enable debugging the issue I am looking at.

Dominant language: WebAssembly
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Merged PRs (30d): 70

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