[Analysis/Allocation] Allocation passes now assumes that slices always alias (#108)

This code in this branch assumes the `src` operand in
`insert_slice_async` always aliases the result, which shouldn't hold for
generally cases but is just a workaround to make the pipeline pass work.

I'm also working on the complete analysis in another
[branch](https://github.com/openai/triton-mlir/tree/keren/analyze-slice).

test/lib/Analysis/TestMembar.cpp

@@ -29,7 +29,7 @@ struct TestMembarPass
     MembarAnalysis analysis(&allocation);
     size_t operationId = 0;
     operation->walk<WalkOrder::PreOrder>([&](Operation *op) {
-      if (dyn_cast<gpu::BarrierOp>(op)) {
+      if (isa<gpu::BarrierOp>(op)) {
         os << "Membar " << operationId << "\n";
       }
       if (op->getNumRegions() == 0) {