30434bab1a
This patch relands https://github.com/llvm/llvm-project/pull/182532. The original version causes test failures related undef bits since it incorrectly assumes `std::uniform_int_distribution` yields the same results across different stdlib vendors. This patch simply uses low bits to avoid the issue. I am not sure whether it still generates uniformly distributed random numbers. But abseil also uses this trick:e72b94a2f2/absl/random/uniform_int_distribution.h (L203-L206)I have confirmed all tests passed with libstdc++ and libc++. Original PR description: Bytes are adjusted to respect the incoming byte type proposed in https://discourse.llvm.org/t/rfc-add-a-new-byte-type-to-llvm-ir/89522. Note that the current implementation of constant folding doesn't handle bitcasts with weird types like `<8 x i3> to <3 x i8>`:49de34459c/llvm/lib/Analysis/ConstantFolding.cpp (L223-L232)So I take the result from Alive2 as reference: https://alive2.llvm.org/ce/z/ZGA_xP
