Silence unnecessary 'host' deprecation warnings

python/tvm/driver/build_module.py

@@ -19,6 +19,8 @@
 """The build utils in python."""
 from typing import Union, Optional, List, Mapping
 
+import warnings
+
 import tvm.tir
 
 from tvm.runtime import Module
@@ -255,8 +257,13 @@ def build(
 
     annotated_mods, target_host = Target.canon_target_map_and_host(annotated_mods, target_host)
 
-    # TODO(mbs): CompilationConfig implements the same host target defaulting logic, but
-    # tir_to_runtime currently bypasses that.
+    # TODO(mbs): Both CompilationConfig and TIRToRuntime implement the same host target
+    #  defaulting logic, but there's currently no way to get back the decided host.
+    if target_host is not None:
+        warnings.warn(
+            "target_host parameter is going to be deprecated. "
+            "Please pass in tvm.target.Target(target, host=target_host) instead."
+        )
     if not target_host:
         for tar, mod in annotated_mods.items():
             device_type = ndarray.device(tar.kind.name, 0).device_type

python/tvm/target/target.py

@@ -247,14 +247,15 @@ def canon_target_and_host(target, target_host=None):
         Note that this method does not support heterogeneous compilation targets.
         """
         target = Target.canon_target(target)
-        target_host = Target.canon_target(target_host)
         if target is None:
             assert target_host is None, "Target host is not empty when target is empty."
-        if target_host is not None:
+            return target, target_host
+        if target.host is None and target_host is not None:
             warnings.warn(
                 "target_host parameter is going to be deprecated. "
                 "Please pass in tvm.target.Target(target, host=target_host) instead."
             )
+            target_host = Target.canon_target(target_host)
             target = target.with_host(target_host)
         if target is not None:
             # In case the target already had a host, extract it here.
@@ -293,15 +294,15 @@ def canon_multi_target_and_host(target, target_host=None):
         """
         # Convert target to Array<Target>, but not yet accounting for any host.
         raw_targets = Target.canon_multi_target(target)
-        assert raw_targets is not None
+        assert raw_targets is not None and len(raw_targets) > 0
         # Convert host to Target, if given.
-        target_host = Target.canon_target(target_host)
-        if target_host is not None:
+        if raw_targets[0].host is None and target_host is not None:
             warnings.warn(
                 "target_host parameter is going to be deprecated. "
                 "Please pass in tvm.target.Target(target, host=target_host) instead."
             )
             # Make sure the (canonical) host is captured in all the (canonical) targets.
+            target_host = Target.canon_target(target_host)
             raw_targets = convert([tgt.with_host(target_host) for tgt in raw_targets])
         return raw_targets
 
@@ -312,22 +313,22 @@ def canon_target_map_and_host(target_map, target_host=None):
         Similarly, if given, target_host can be in any form recognized by
         Target.canon_target. The final target_map keys will capture the target_host in
         canonical form. Also returns the target_host in canonical form."""
-        if target_host is not None:
-            warnings.warn(
-                "target_host parameter is going to be deprecated. "
-                "Please pass in tvm.target.Target(target, host=target_host) instead."
-            )
-            target_host = Target.canon_target(target_host)
         new_target_map = {}
+        canonical_target_host = None
         for tgt, mod in target_map.items():
             tgt = Target.canon_target(tgt)
             assert tgt is not None
-            if target_host is not None:
-                tgt = tgt.with_host(target_host)
-            # In case the first target already has a host, extract it here.
-            target_host = tgt.host
+            if canonical_target_host is None:
+                if tgt.host is not None:
+                    canonical_target_host = tgt.host
+                elif target_host is not None:
+                    # No deprecation warning in this case since host may have been manufactured
+                    # behind the scenes in build_module.py build.
+                    canonical_target_host = Target.canon_target(target_host)
+            if tgt.host is None and canonical_target_host is not None:
+                tgt = tgt.with_host(canonical_target_host)
             new_target_map[tgt] = mod
-        return new_target_map, target_host
+        return new_target_map, canonical_target_host
 
     @staticmethod
     def target_or_current(target):