_mm_maskmoveu_si128 requires mutable in-bounds memory even when it does nothing

[RalfJung]

That's what @programmerjake said, anyway. The Intel docs don't mention this...

I have no idea if other intrinsics have similar requirements.

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[RalfJung]

@folkertdev @Amanieu friendly review reminder. :)

[folkertdev]

I found

https://www.intel.com/content/dam/support/us/en/documents/processors/pentium4/sb/253669.pdf

An execution of the MASKMOVQ or MASKMOVDQU instructions with a zero mask
may or may not cause a page fault or an EPT violation if the destination page is
unwritable (the behavior is implementation-specific).

https://bluewaters.ncsa.illinois.edu/liferay-content/document-library/amd_4_26568.pdf

Exception and trap behavior for elements not selected for storage to memory is implementation
dependent. For instance, a given implementation may signal a data breakpoint or a page fault for
bytes that are zero-masked and not actually written.

So that seems pretty clear.

[RalfJung]

Thanks!

An execution of the MASKMOVQ or MASKMOVDQU instructions

So does this affect other intrinsics beyond _mm_maskmoveu_si128?