DXC not optimizing out code related to groupshared

For shader like this:
groupshared float a[10];
[numthreads(8,8,1)]
void main() {
a[0] = 1;
}
the output dxil is this:
@"\01?a@@3PAMA" = external addrspace(3) global [10 x float], align 4

define void @main() {
store float 1.000000e+00, float addrspace(3)* getelementptr inbounds ([10 x float], [10 x float] addrspace(3)* @"\01?a@@3PAMA", i32 0, i32 0), align 4, !tbaa !7
ret void
}

Expect the store and the global variable to be removed because there's only store on the global variabl.

Start with the HLSL reproducer in the issue and inspect the generated DXIL for the groupshared global and its store. Trace the optimization path that handles this shader and add or run a regression test; done means both the unused global and its store are absent from the output.