Store→Load Reordering: x86 vs ARM64 Real-World Test

What really happens when CPUs reorder your instructions. Side-by-side experiment putting store→load reordering to the test on x86-64 and ARM64.

August 3, 2025
Harrison Guo
Video by: HarrisonSecurityLab
Published on YouTube: 2025-08-03
Memory Model x86 ARM64 Concurrency CPU Memory Fences Lock-Free

Same C code, two architectures, two different observable behaviors. x86-64’s TSO model hides store→load reordering most of the time; ARM64’s weaker model lets you see it directly. This video runs a minimal test that demonstrates the difference and prints the reorder count.

If you’ve written lock-free code that “worked on x86 but broke on ARM,” this is the underlying mechanism.

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