[SVE] Use only powers of two as possible vscale values #17001
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When analyzing scalable expressions, the analyzer will iterate over a series of known vscale values in the range 1-16. However, we can tighten this range to only values that are a power of two, as stated in the [LLVM lang ref](https://llvm.org/docs/LangRef.html#llvm-vscale-intrinsic:~:text=This%20function%20attribute%20indicates%20vscale%20is%20a%20power%2Dof%2Dtwo%20within%20a%20specified%20range) and more generally the [reference manual](https://developer.arm.com/documentation/ddi0487/latest/). This comes from a discussion in apache#16921 (comment) Change-Id: Iabbd1478b3853c3a6ad49c1442422bd50b8b08a6
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Credit here is to @Anndrey24 ;) |
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When analyzing scalable expressions, the analyzer will iterate over a series of known vscale values in the range 1-16. However, we can tighten this range to only values that are a power of two, as stated in the LLVM lang ref and more generally the reference manual.
This comes from a discussion in #16921 (comment)