Add Vela codebase

 - Added modules ethosu.vela and ethosu.mlw_codec.
 - Added README and various configuration files.

Change-Id: I3690f8c8f5966306ecddaeb2793c30ca9c6e2eee
diff --git a/ethosu/vela/tensor_allocation.py b/ethosu/vela/tensor_allocation.py
new file mode 100644
index 0000000..94aa608
--- /dev/null
+++ b/ethosu/vela/tensor_allocation.py
@@ -0,0 +1,139 @@
+# Copyright (C) 2020 Arm Limited or its affiliates. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the License); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an AS IS BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# Description:
+# Wrapping function to do tensor address allocation. That is, assigning addresses to tensors based on what has been
+# worked out from the allowable overlaps that are calculated by the live range analysis.
+
+from . import live_range
+from .tensor import MemArea
+import math
+from . import numeric_util
+import numpy as np
+from .nn_graph import TensorAllocator, PassPlacement
+
+from .greedy_allocation import allocate_live_ranges as greedy_allocate_live_ranges
+
+
+def linear_allocate_live_ranges(live_ranges, alloc_granularity=256):
+    total_sz = 0
+    allocated_tensors = []
+
+    # just assign increasing addresses
+    for tens, lr in live_ranges.ranges.items():
+        if tens in allocated_tensors:
+            continue
+
+        lr.set_address(total_sz)
+        allocated_tensors += lr.tensors
+        total_sz += numeric_util.round_up(int(math.ceil(lr.size)), alloc_granularity)
+
+    return total_sz
+
+
+def mark_sram_used_for_cascaded_passes(sg, lrs):
+    end_pos = max(ps.time for ps in sg.cascaded_passes) + 2
+    mem_usage = np.zeros(end_pos, dtype=np.int64)
+
+    for tens, rng in lrs.ranges.items():
+        storage_size = tens.storage_size()
+        mem_usage[rng.start_time : rng.end_time] += storage_size
+
+    for cps in sg.cascaded_passes:
+        sram_used = max(mem_usage[cps.time], mem_usage[cps.time + 1])
+        cps.sram_used = sram_used
+        for ps in cps.passes:
+            ps.sram_used = sram_used
+
+
+def print_allocation(lrs, mem_area, sg, verbose_allocation, show_minimum_possible_allocation):
+    if verbose_allocation:
+        if mem_area == MemArea.Sram:
+            print("allocation for", mem_area, "- non-constant tensors in Cpu and Npu subgraphs")
+        else:
+            print("allocation for", mem_area, "- constant tensors in", sg.placement.name, "subgraph(s)")
+        for start_time, start, end, name, end_time in sorted(
+            (
+                lr.start_time,
+                tens.address,
+                tens.address + int(math.ceil(tens.storage_size())),
+                tens.name + " " + str(tens.purpose),
+                lr.end_time,
+            )
+            for tens, lr in lrs.ranges.items()
+        ):
+            name = name.replace("\x00", "")
+            print("%9d: %#12x - %#12x: %3d - %3d %s" % ((end - start), start, end, start_time, end_time, name))
+        print()
+
+    if show_minimum_possible_allocation and mem_area == MemArea.Sram:
+        min_possible_allocation = max(cps.sram_used for cps in sg.cascaded_passes)
+        print(
+            "Min possible allocation %d bytes / %.1f KB / %.1f MB"
+            % (min_possible_allocation, min_possible_allocation / 1024, min_possible_allocation / 1024 / 1024)
+        )
+
+
+def allocate_tensors(
+    nng,
+    sg,
+    arch,
+    mem_area,
+    use_ifm_ofm_overlap=True,
+    tensor_allocator=TensorAllocator.Greedy,
+    verbose_allocation=False,
+    show_minimum_possible_allocation=False,
+    lr_graph=None,
+):
+    ignore_subgraph_input_output_tensors = False
+    lrs = live_range.extract_live_ranges_from_cascaded_passes(
+        sg,
+        mem_area,
+        mark_output_tensors_overlapping_with_input_tensors=False,
+        use_ifm_ofm_overlap=use_ifm_ofm_overlap,
+        ignore_subgraph_input_output_tensors=ignore_subgraph_input_output_tensors,
+        lr_graph=lr_graph,
+    )
+
+    if lrs.ranges:
+        tens_alloc = tensor_allocator
+        if tens_alloc == TensorAllocator.Greedy:
+            total_sz = greedy_allocate_live_ranges(sg, arch, lrs, mem_area, verbose_allocation)
+        elif tens_alloc == TensorAllocator.LinearAlloc:
+            total_sz = linear_allocate_live_ranges(lrs)
+        else:
+            assert 0
+
+        sg.memory_used[mem_area] = total_sz
+
+        nng.total_size[mem_area] = nng.total_size.get(mem_area, 0) + sum(tens.storage_size() for tens in lrs.ranges)
+        nng.total_elements[mem_area] = nng.total_elements.get(mem_area, 0) + sum(tens.elements() for tens in lrs.ranges)
+
+        print_allocation(lrs, mem_area, sg, verbose_allocation, show_minimum_possible_allocation)
+
+        if mem_area == MemArea.Sram:
+            # Mark Sram usage for all subgraphs
+            for sg_ in nng.subgraphs:
+                mark_sram_used_for_cascaded_passes(sg_, lrs)
+
+    if sg == nng.get_root_subgraph():
+        nng.memory_used = sg.memory_used
+        for mem_area in nng.total_elements.keys():
+            try:
+                nng.bits_per_element[mem_area] = nng.total_size[mem_area] * 8 / nng.total_elements[mem_area]
+            except ZeroDivisionError:
+                nng.bits_per_element[mem_area] = 0.0