Added trait NoMemoryEffect to assume_alignment

Assume_alignment has no trait which specifies how it interacts with
memory, this causes an issue in OwnershipBasedBufferDeallocation,
which require all operations which operate on buffers to have explicit
traits defining how the operation interacts with memory.

From my understanding, technically the operation is pure, however to make
sure the operation doesn't get optimized away it has to have some side
effect. I defined it to have similar side effects to CF AssertOp as both
are asserts. I'm not sure if this is correct and would appreciate the
opinion of someone more experienced.

Author: Shay Kleiman

mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td

@@ -142,7 +142,7 @@ class AllocLikeOp<string mnemonic,
 // AssumeAlignmentOp
 //===----------------------------------------------------------------------===//
 
-def AssumeAlignmentOp : MemRef_Op<"assume_alignment"> {
+def AssumeAlignmentOp : MemRef_Op<"assume_alignment",[DeclareOpInterfaceMethods<MemoryEffectsOpInterface>]> {
   let summary =
       "assertion that gives alignment information to the input memref";
   let description = [{

mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp

@@ -526,6 +526,11 @@ LogicalResult AssumeAlignmentOp::verify() {
     return emitOpError("alignment must be power of 2");
   return success();
 }
+void AssumeAlignmentOp::getEffects(
+  SmallVectorImpl<SideEffects::EffectInstance<MemoryEffects::Effect>>
+      &effects) {
+effects.emplace_back(MemoryEffects::Write::get());
+}
 
 //===----------------------------------------------------------------------===//
 // CastOp