[TVMScript] Allow T.target("device", host="host") to specify host (ap…

…ache#14915)

[TVMScript] Allow T.target("device", host="host") in TVMScript

Prior to this commit, the `TargetNode::host` could be specified in
TVMScript as part of the config dictionary, under the key `"host"`.
However, this required all other device parameters to be explicitly
specified, rather than using any of the short-hand string
representations.  This commit forwards the `host` argument from TVMScript's
`T.target` method to `tvm.target.Target`, allowing both the device and
host to be specified using the shorthand string representation.

```python
@T.prim_func
def before_this_commit():
    T.func_attr(
        {
            "target": T.target(
                {
                    "arch": "sm_86",
                    "host": {"keys": ["cpu"], "kind": "llvm", "tag": ""},
                    "keys": ["cuda", "gpu"],
                    "kind": "cuda",
                    "max_num_threads": 1024,
                    "tag": "",
                    "thread_warp_size": 32,
                }
            )
        }
    )
    T.evaluate(0)

@T.prim_func
def after_this_commit():
    T.func_attr({"target": T.target("cuda", host="llvm")})
    T.evaluate(0)
```

python/tvm/script/ir_builder/tir/ir.py

@@ -1655,7 +1655,10 @@ def index_map(
     return IndexMap.from_func(mapping, inverse_index_map=inverse_index_map)
 
 
-def target(target_config: Union[Dict, str]) -> Target:
+def target(
+    target_config: Union[Dict, str],
+    host: Optional[Union[Dict, str, Target]] = None,
+) -> Target:
     """
     Create a target
 
@@ -1664,6 +1667,9 @@ def target(target_config: Union[Dict, str]) -> Target:
     target_config : Union[Dict, str]
         The target configuration.
 
+    host : Optional[Union[Dict, str, Target]]
+        The target configuration.
+
     Returns
     -------
     res : Target
@@ -1673,7 +1679,19 @@ def target(target_config: Union[Dict, str]) -> Target:
         raise ValueError(
             f"T.target expected a config dict or string, but got {type(target_config)}"
         )
-    return Target(target_config)
+    if host is not None and not isinstance(host, (str, dict, Target)):
+        raise ValueError(
+            "T.target expected the host to be "
+            "a config dict, string, or T.target, "
+            f"but got {type(host)}"
+        )
+    if isinstance(target_config, dict) and "host" in target_config and host is not None:
+        raise ValueError(
+            "T.target expects to either receive the host "
+            "as part of the target's config dictionary, "
+            "or as a separate argument, but not both."
+        )
+    return Target(target_config, host)
 
 
 def Range(begin: PrimExpr, end: PrimExpr) -> ir.Range:  # pylint: disable=invalid-name

tests/python/unittest/test_tvmscript_roundtrip.py

@@ -3123,6 +3123,15 @@ def func_with_target_spec_by_str() -> None:
     return func_with_target_spec_by_str
 
 
+def func_with_target_and_host_spec_by_str():
+    @T.prim_func
+    def func():
+        T.func_attr({"target": T.target("nvidia/nvidia-a100", host="llvm")})
+        T.evaluate(0)
+
+    return func
+
+
 def func_root_attr():
     @T.prim_func
     def func_root_attr():
@@ -3883,6 +3892,7 @@ def func():
     nontrivial_range_axis,
     func_with_target_spec_by_config,
     func_with_target_spec_by_str,
+    func_with_target_and_host_spec_by_str,
     func_root_attr,
     func_trivial_root_block,
     func_nested_root_block,