GlobalISel missing divide-by-pow2 special case expansions

[arsenm]

The DAG has special handling for divide by a power of 2. This is an optimization that also handles some legalization work for large cases that require expansion. Since this is missing, i128 divides do not work for AMDGPU on GlobalISel

[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

The DAG has special handling for divide by a power of 2. This is an optimization that also handles some legalization work for large cases that require expansion. Since this is missing, i128 divides do not work for AMDGPU on GlobalISel

[shiltian]

Fixed in #83155.