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It can make a difference due to weird ABIs. For example, in the ARM procedure call standard, 64-bit values can be returned in r0 and r1, but 64-bit structures can't (no matter whether they contain two 32-bit values or just one 64-bit value). However, I'd call that fairly niche - it's hard to imagine an application that would notice a significant performance difference.

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This is very nice to know actually, and quite relevant to code I am working on right now!

Disappointing though.

> it's hard to imagine an application that would notice a significant performance difference.

One hopes any function call made often enough to be a perf hit from this would also be designed to be easily inlined!

Scientific computing will hit this sort of problem just because the kernel is so large it actually needs to be broken into sub-procedures for icache reasons. But also, the penalty is large, because there is a full store/load cycle involved, which will clear caches and increase memory bandwidth requirements.

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