[PATCH] D139827: [RISCV][Asan] Use dynamic shadow offset to make it work on different width of virtual-memory system.

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka added a comment.

In D139827#4038014 <https://reviews.llvm.org/D139827#4038014>, @MaskRay wrote:

>> The original asan port was support Sv39 only, however Sv48 support has landed to linux kernel[1] for a while, so we are trying to make it support both Sv39 and Sv48,
>
> Supporting too many address space bits can introduce significant hidden maintenance burden and performance implication, e.g. using SizeClassAllocator32 for LeakSanitizer (standalone or asan/hwasan integrated) is extremely slow.
> See `D137666` that AArch64 msan dropped `<48`-bit VMA. A line needs to be drawn.

+1
Also overhead of dynamic shadow is quite significant, it dependents on hardware. So it would be nice if you can just drop smaller address spaces.


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