[clang] [llvm] [Clang][ARM] Fix immediate range for NEON widening left-shifts (PR #212459)

[David Green via llvm-commits]

davemgreen wrote:

It would appear that GCC accepts a limit upto eltsize/2, and I see examples in the wild for immediates that high https://github.com/search?q=vshll_n_s8&type=code

https://github.com/llvm/llvm-project/pull/212459