deps: backport V8 LLE alias fix to 26.x and 24.x

Summary

Please backport V8 commit b44239fe / V8 bug 554421904, "Turboshaft LLE: non-writing calls can create aliases", to the active Node.js 26.x and 24.x release lines.

This is the same upstream V8 miscompilation tracked in #66083 for 26.x, but 24.x is also affected by default: Node 24 ships V8 13.6 with Turboshaft load elimination enabled by default, and the minimized reproducer returns the wrong value there too.

Version

Reproduced locally with:

• v26.9.0 / V8 14.6.202.34-node.32
• v24.18.0 / V8 13.6.233.17-node.50

Source check after fetching current tags/branches:

• upstream/v26.x and upstream/v26.x-staging: V8 14.6.202.34, no regress-554421904 test
• upstream/v24.x and upstream/v24.x-staging: V8 13.6.233.17, no regress-554421904 test

Platform

macOS arm64

This appears to be a compiler optimization bug rather than platform-specific behavior.

Subsystem

V8 / deps

What steps will reproduce the bug?

Run the minimized reproducer from #66083 with native syntax enabled:

node --allow-natives-syntax v8-lle-poc.js

I also checked the relevant runtime flag defaults:

• 26.x: --turboshaft-load-elimination is enabled by default
• 24.x: --turboshaft-load-elimination is enabled by default
• 22.x: --turboshaft-load-elimination is disabled by default, so this request is intentionally limited to 26.x and 24.x

How often does it reproduce? Is there a required condition?

It reproduced consistently for me on both default-affected lines listed above.

The reproducer requires optimized code and the Turboshaft load-elimination pass. That pass is enabled by default on the Node 26 and Node 24 builds tested.

What is the expected behavior? Why is that the expected behavior?

The store to staleArray[7] should be preserved, so the returned array slot should contain 1.1:

staleArray[7]: 1.1 | expected: 1.1 | OK
RESULT: NOT TRIGGERED on this build

What do you see instead?

Node 26:

v26.9.0 V8 14.6.202.34-node.32
staleArray[7]: undefined | expected: 1.1 | WRONG!
RESULT: BUG TRIGGERED — Turboshaft LLE eliminated a valid store

Node 24:

v24.18.0 V8 13.6.233.17-node.50
staleArray[7]: undefined | expected: 1.1 | WRONG!
RESULT: BUG TRIGGERED — Turboshaft LLE eliminated a valid store

Additional information

The upstream fix is small and directly addresses the alias invalidation ordering in Turboshaft late load elimination:

• Fix: https://chromium.googlesource.com/v8/v8/+/b44239fe
• Review: https://chromium-review.googlesource.com/c/v8/v8/+/8345010
• V8 bug: 554421904

The current 26.x and 24.x V8 snapshots still have the vulnerable early !op.Effects().can_write() bailout before invalidating non-aliasing inputs in deps/v8/src/compiler/turboshaft/late-load-elimination-reducer.cc.

Start with deps/v8/src/compiler/turboshaft/late-load-elimination-reducer.cc and compare the active 26.x and 24.x V8 snapshots with upstream commit b44239fe. Run v8-lle-poc.js using node --allow-natives-syntax on both release lines, then verify that the upstream fix and regress-554421904 coverage are present and the reproducer returns 1.1.