Address feedback

python/tvm/contrib/binutil.py

@@ -38,8 +38,8 @@ def tvm_callback_get_section_size(binary_path, section_name, toolchain_prefix):
     toolchain_prefix : str
         prefix for binary names in target compiler toolchain
 
-    Return
-    ------
+    Returns
+    -------
     size : integer
         size of the section in bytes
     """
@@ -61,8 +61,8 @@ def tvm_callback_get_section_size(binary_path, section_name, toolchain_prefix):
     section_mapping = {
         ".text": [".text"],
         ".rodata": [".rodata"],
-        ".data": [".data"],
-        ".bss": [".bss", ".sbss", ".sdata"],
+        ".data": [".data", ".sdata"],
+        ".bss": [".bss", ".sbss"],
     }
     sections_to_sum = section_mapping["." + section_name]
     section_size = 0
@@ -103,8 +103,8 @@ def tvm_callback_relocate_binary(
     toolchain_prefix : str
         prefix for binary names in target compiler toolchain
 
-    Return
-    ------
+    Returns
+    -------
     rel_bin : bytearray
         the relocated binary
     """
@@ -114,8 +114,6 @@ def tvm_callback_relocate_binary(
     # TODO(weberlo): There should be a better way to configure this for different archs.
     if "riscv" in toolchain_prefix:
         ld_script_contents += "OUTPUT_ARCH( \"riscv\" )\n\n"
-    # TODO(weberlo): *Should* ".sdata" and ".sbss" be linked into the ".bss"
-    # section?
     # TODO(weberlo): Generate the script in a more procedural manner.
     ld_script_contents += """
 SECTIONS
@@ -143,6 +141,8 @@ def tvm_callback_relocate_binary(
     *(.data)
     . = ALIGN(8);
     *(.data*)
+    . = ALIGN(8);
+    *(.sdata)
   }
   . = %s;
   . = ALIGN(8);
@@ -153,8 +153,6 @@ def tvm_callback_relocate_binary(
     *(.bss*)
     . = ALIGN(8);
     *(.sbss)
-    . = ALIGN(8);
-    *(.sdata)
   }
 }
     """ % (text_addr, rodata_addr, data_addr, bss_addr)
@@ -191,8 +189,8 @@ def tvm_callback_read_binary_section(binary, section, toolchain_prefix):
     toolchain_prefix : str
         prefix for binary names in target compiler toolchain
 
-    Return
-    ------
+    Returns
+    -------
     section_bin : bytearray
         contents of the read section
     """
@@ -233,8 +231,8 @@ def tvm_callback_get_symbol_map(binary, toolchain_prefix):
     toolchain_prefix : str
         prefix for binary names in target compiler toolchain
 
-    Return
-    ------
+    Returns
+    -------
     map_str : str
         map of defined symbols to addresses, encoded as a series of
         alternating newline-separated keys and values

python/tvm/micro/base.py

@@ -21,6 +21,7 @@
 
 import logging
 import os
+import sys
 
 from tvm.contrib import util as _util
 from tvm.contrib import cc as _cc
@@ -57,6 +58,7 @@ class Session:
     def __init__(self, device_type, toolchain_prefix):
         if device_type not in SUPPORTED_DEVICE_TYPES:
             raise RuntimeError("unknown micro device type \"{}\"".format(device_type))
+        self._check_system()
 
         # First, find and compile runtime library.
         runtime_src_path = os.path.join(_get_micro_device_dir(), "utvm_runtime.c")
@@ -69,6 +71,18 @@ def __init__(self, device_type, toolchain_prefix):
         self._enter = self.module["enter"]
         self._exit = self.module["exit"]
 
+    def _check_system(self):
+        """Check if the user's system is supported by MicroTVM.
+
+        Raises error if not supported.
+        """
+        if not sys.platform.startswith("linux"):
+            raise RuntimeError("microTVM is currently only supported on Linux")
+        # TODO(weberlo): Add 32-bit support.
+        # It's primarily the compilation pipeline that isn't compatible.
+        if sys.maxsize <= 2**32:
+            raise RuntimeError("microTVM is currently only supported on 64-bit platforms")
+
     def __enter__(self):
         self._enter()
 
@@ -167,9 +181,9 @@ def replace_suffix(s, new_suffix):
     options = ["-I" + path for path in find_include_path()]
     options += ["-I{}".format(_get_micro_device_dir())]
     options += ["-fno-stack-protector"]
-    # TODO(weberlo): This option cannot be used on 32-bit machines. Make this
-    # compilation pipeline compatible with 32-bit.
-    options += ["-mcmodel=large"]
+    if sys.maxsize > 2**32 and sys.platform.startswith("linux"):
+        # Only add this option if the host is a 64-bit Linux.
+        options += ["-mcmodel=large"]
     compile_cmd = "{}gcc".format(toolchain_prefix)
 
     if include_dev_lib_header:

src/runtime/micro/micro_session.cc

@@ -21,6 +21,16 @@
  *  Copyright (c) 2019 by Contributors
  * \file micro_session.cc
  * \brief session to manage multiple micro modules
+ *
+ * Each session consists of an interaction with a *single* logical device.
+ * Within that interaction, multiple TVM modules can be loaded on the logical
+ * device.
+ *
+ * Multiple sessions can exist simultaneously, but there is only ever one
+ * *active* session. The idea of an active session mainly has implications for
+ * the frontend, in that one must make a session active in order to allocate
+ * new TVM objects on it. Aside from that, previously allocated objects can be
+ * used even if the session which they belong to is not currently active.
  */
 
 #include <dmlc/thread_local.h>

tests/python/contrib/test_binutil.py

@@ -14,13 +14,23 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+"""Test various utilities for interaction with compiled binaries.
+
+Specifically, we test the following capabilities:
+  - querying the size of a binary section
+  - relocating sections within a binary to new addresses
+  - reading the contents of a binary section
+  - querying the address of a symbol in the binary
+"""
 
 import tvm
 import subprocess
 from tvm.contrib import util
 from tvm.contrib import cc
 from tvm.contrib.binutil import *
 
+TOOLCHAIN_PREFIX = ""
+
 def make_binary():
     prog = "int a = 7; \
             int main() { \
@@ -29,19 +39,15 @@ def make_binary():
             }"
     tmp_dir = util.tempdir()
     tmp_source = tmp_dir.relpath("source.c")
-    tmp_obj = tmp_dir.relpath("obj.o")
+    tmp_obj = tmp_dir.relpath("obj.obj")
     with open(tmp_source, "w") as f:
         f.write(prog)
-    p1 = subprocess.Popen(["gcc", "-c", tmp_source, "-o", tmp_obj],
-                           stdout=subprocess.PIPE,
-                           stderr=subprocess.STDOUT)
-    p1.communicate()
+    cc.create_shared(tmp_obj, tmp_source, [],
+                     compile_cmd="{}gcc".format(TOOLCHAIN_PREFIX))
     prog_bin = bytearray(open(tmp_obj, "rb").read())
     return prog_bin
 
 
-TOOLCHAIN_PREFIX = ""
-
 def test_tvm_callback_get_section_size(binary=None):
     if binary is None:
         binary = make_binary()

tests/python/unittest/test_runtime_micro.py

@@ -268,6 +268,33 @@ def test_nested_sessions():
                 add_result, np_tensor_a + 1.0)
 
 
+def test_inactive_session_use():
+    """Test the use of objects allocated in a session that is no longer active."""
+    if not tvm.module.enabled("micro_dev"):
+        return
+    shape = (1024,)
+    dtype = "float32"
+
+    # Construct Relay add program.
+    x = relay.var("x", relay.TensorType(shape=shape, dtype=dtype))
+    ret = relay.add(x, relay.const(1.0))
+    add_const_func = relay.Function([x], ret)
+
+    sess_a = micro.Session(DEVICE_TYPE, TOOLCHAIN_PREFIX)
+    sess_b = micro.Session(DEVICE_TYPE, TOOLCHAIN_PREFIX)
+    with sess_a:
+        np_tensor_a = np.random.uniform(size=shape).astype(dtype)
+        micro_tensor_a = tvm.nd.array(np_tensor_a, tvm.micro_dev(0))
+        add_const_mod = relay_micro_build(add_const_func, TOOLCHAIN_PREFIX)
+
+    with sess_b:
+        # These objects belong to `sess_a`.
+        add_const_mod.run(x=micro_tensor_a)
+        add_result = add_const_mod.get_output(0).asnumpy()
+        tvm.testing.assert_allclose(
+                add_result, np_tensor_a + 1.0)
+
+
 if __name__ == "__main__":
     test_alloc()
     test_add()
@@ -276,3 +303,4 @@ def test_nested_sessions():
     test_multiple_modules()
     test_interleave_sessions()
     test_nested_sessions()
+    test_inactive_session_use()