Original commit message: [wasm] Fix jump table slot overflow on x64 with CET enabled JumpTableAssembler::EmitJumpSlot for x64 was advancing the PC before checking if the target was reachable via a 32-bit displacement when CET was enabled. This caused a slot overflow when the far-jump fallback was triggered, as the second attempt to emit the slot would start at an incorrect offset. This CL ensures that the displacement check is performed before any instructions are emitted, making the function side-effect-free on failure. It also introduces kJumpTableSlotEntryMarkerSize to clarify the displacement calculation, following the pattern used on ARM64. Reported-by: Fabien Romano <fabienromano@gmail.com> TAG=agy R=jkummerow@chromium.org Fixed: 532112743 Change-Id: Iaf6f15b51a66a45711e8556972ac0d353e6117c7 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/8063803 Reviewed-by: Jakob Kummerow <jkummerow@chromium.org> Commit-Queue: Clemens Backes <clemensb@chromium.org> Cr-Commit-Position: refs/heads/main@{#108556} Refs: v8/v8@1158ae7 PR-URL: #64432 Fixes: #64424 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Richard Lau <richard.lau@ibm.com>

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WASM far-jump crashes on x64 with CET enabled #64424

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