[webkit-changes] [WebKit/WebKit] d8ada2: [Wasm-GC] Fix br_on_cast issue on BBQ

[Asumu Takikawa]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: d8ada2256e9ea1791dd26c1673bb27ae97eb4711
      https://github.com/WebKit/WebKit/commit/d8ada2256e9ea1791dd26c1673bb27ae97eb4711
  Author: Asumu Takikawa <asumu at igalia.com>
  Date:   2024-03-11 (Mon, 11 Mar 2024)

  Changed paths:
    M JSTests/wasm/gc/br_on_cast.js
    M Source/JavaScriptCore/wasm/WasmBBQJIT32_64.cpp
    M Source/JavaScriptCore/wasm/WasmBBQJIT64.cpp

  Log Message:
  -----------
  [Wasm-GC] Fix br_on_cast issue on BBQ
https://bugs.webkit.org/show_bug.cgi?id=268848

Reviewed by Justin Michaud.

While this error occurs in sample code using br_on_cast, it appears the bug is
actually in struct.get. Instead of `loadIfNecessary`, an `allocate` was used
for the struct ref. This doesn't work in the case that the ref gets spilled to
the stack due to, e.g., a runtime call.

This is just easy to trigger with br_on_cast, which currently always does a
runtime call for the cast part on BBQJIT and will likely spill the ref.

* JSTests/wasm/gc/br_on_cast.js:
* Source/JavaScriptCore/wasm/WasmBBQJIT64.cpp:
(JSC::Wasm::BBQJITImpl::BBQJIT::addStructGet):
* Source/JavaScriptCore/wasm/WasmBBQJIT32_64.cpp:
(JSC::Wasm::BBQJITImpl::BBQJIT::addStructGet):

Canonical link: https://commits.webkit.org/275920@main



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