* Add TopK to ONNX Frontend

* respond to review comments

* [RELAY][PYTORCH]cosh,sinh,log2,log10,log1p op support

* Review comment fixed

* Gradient testcase added

The _type_child_slots can be used to enable quick type checking optimization
by checking the whether the type index is within the bound.

This PR enables these static slots:

- Introduce a static assert to avoid the scenario when a developer forget to
  _type_child_slots when the field is set for the type's parent.
- Revamp and assign static type index to common runtime objects
- Add a DumpTypeTable call to allow developer monitor the current situation
  of type table and offers suggestions for the slots(ideally the slots equals
  the number of children so there is no overflow.

Added missing "tir" in tvm.tir.analysis.verify_gpu_code(f, kwargs)

* [FRONTEND][TFLITE]Gather, StridedSlice op added

* Review comments fixed

* [PYTORCH]Where, addcdiv, addcmul op support

* Review comments fixed

To make runtime.String to work as naturally as possible in the python side,
we make it sub-class the python's str object. Note that however, we cannot
sub-class Object at the same time due to python's type layout constraint.

We introduce a PyNativeObject class to handle this kind of object sub-classing
and updated the FFI to handle PyNativeObject classes.

* [RFC] Pass pytest options globally.

In many places having a global pytest flag is useful . For me with the
build and test of tvm , I would like to be able to globally pass in
pytest options as part of development flow or CI flows where one would
like to measure other things regularly that need measurements including
pytest coverage data that I would like to experiment with across the stack.

This has been achieved with an additional setup-pytest-env.sh file in
tests/scripts rather than putting in something in every single task test
script and something I would like to avoid.

This now means the -v option to pytest is superfluous. I did consider
having a pytest.ini file but that doesn't allow me to pass any old
environment variable in and this seems to be the compromise.

* Improve other use case documentation

* Rationalize pytest environment.

* Remove the setting from docker/with_same_user.
* Take the opportunity to migrate common PYTHONPATH and
TVM_PATH into the common environment setting.

* Fixup vta fsim

* Be more explicit with common PYTHONPATH

* Fix python path for task_python_vta_fsim.sh properly

* Fix nit in documentation.

* Non-Recursive AnnotatedTarget and MergeAnnotation

* Non-Recursive AnnotatedRegionSet and RegionMerger

* [DOCS] Migrate some markdowns to rst, fix sphinx3 warnings

* Add note block

* Migrate Tensorflow and TFLite in the CI up to 1.15.2

The latest stable version of Tensorflow and Tensorflow lite
in the 1.x series is 1.15.2. The tflite frontend is receiving
support for versions of tflite > 1.14 but there is no consistent
testing.

There are 2 failures already in the source base with tf 1.15
and I'm concerned this will just get exacerbated over time
if we don't have CI picking this up and I view this as a stepping
stone towards stepping CI to TF2.x.

The test failures that I have commented will get issues raised
for them as issues to be fixed.

* Comment out run of qnn_mobilenet_v3_net

This is another test that fails with TFlite 1.15.2

* Skip the qnn_mobilenet_v3 test in the pytest fashion.

* Switch docker versions to support Tensorflow 2.1.0

* Fix up pytest imports and usage.

* Skip these tests currently for Tensorflow 2.1.0

Signed-off-by: Wei Pan <weip@nvidia.com>

* [RUNTIME][CONTRIB] CoreML Runtime

* fix lint

* fix CI

* use xcrun to compile coreml model

This PR removes ir_pass(old style pass functions) in favor
of analysis/transform(new style pass manager).

* Use atexit to remove TempDirectory before interpreter shutdown.
 * Can't rely on complex functions from __del__ anyway.
 * Fixes warning message on my box:
       Exception ignored in: <function TempDirectory.__del__ at 0x12be10680>
       Traceback (most recent call last):
        File ".../tvm/python/tvm/contrib/util.py", line 55, in __del__
        File ".../tvm/python/tvm/contrib/util.py", line 51, in remove
        File "/usr/local/opt/python/Frameworks/Python.framework/Versions/3.7/lib/python3.7/shutil.py", line 509, in rmtree
        AttributeError: 'NoneType' object has no attribute 'path'

This function has recently been removed from LLVM 11. Use alternative
way to obtain vector element count (VectorType::getNumElements) which
works for all LLVM versions.

* Customize SI prefix in logging

* Include unit test

Substitute now takes a std::function to customize more replacing behaviors.

Co-authored-by: Siyuan Feng <hzfengsy@sjtu.edu.cn>

Co-authored-by: Siyuan Feng <hzfengsy@sjtu.edu.cn>

* Restructure imports in tflite frontend.

These python modules are needed for every tflite file parsed.
Factorize out imports of the common most ones.

Now that the import of operator is common, asserts can be commonized.

Loses 473 lines of duplication.

* Only restrict to tflite.Operator

This switch was made in LLVM 11. Previously this function was expecting
mask indices of type uint32_t. This variant is now deprecated.

* Fix oversight in importing tf.compat.v1 as tf.

* Actually disable test for lstm in TF2.1

Since the testing framework actually uses pytest, the version
check needs to be moved.

* The void return type is not None/nullptr, it's VoidType or
   TupleType([]).

* [Topi, ARM] Disbale Winograd for quantized tensors.

* Relaxing float

The legacy Simplify/CanonicalSimplify are now a thin wrapper around the Analyzer.
This PR removes these functions and migrated every place that requires
simplification to enforce Analyzer creation.
The new API would encourage more Analyzer sharing and potentially enable
context-aware analyzer-based simplification.