[FIX] Improve error messages and docs (apache#7064)

- Better document tvm.relay.create_executor
- Print what was provided in src/target/llvm/llvm_module.cc,
  src/tir/transforms/arg_binder.cc,
  src/tir/transforms/storage_rewrite.cc

python/tvm/relay/build_module.py

@@ -408,10 +408,26 @@ def _graph_wrapper(*args, **kwargs):
 def create_executor(kind="debug", mod=None, ctx=None, target="llvm"):
     """Factory function to create an executor.
 
+    Example
+    -------
+    .. code-block:: python
+
+        import tvm.relay
+        import numpy as np
+
+        x = tvm.relay.var("x", tvm.relay.TensorType([1], dtype="float32"))
+        expr = tvm.relay.add(x, tvm.relay.Constant(tvm.nd.array(np.array([1], dtype="float32"))))
+        tvm.relay.create_executor(
+            kind="vm", mod=tvm.IRModule.from_expr(tvm.relay.Function([x], expr))
+        ).evaluate()(np.array([2], dtype="float32"))
+        # returns `array([3.], dtype=float32)`
+
     Parameters
     ----------
     kind : str
-        The type of executor
+        The type of executor. Avaliable options are `debug` for the
+        interpreter, `graph` for the graph runtime, and `vm` for the virtual
+        machine.
 
     mod : :py:class:`~tvm.IRModule`
         The Relay module containing collection of functions
@@ -421,6 +437,10 @@ def create_executor(kind="debug", mod=None, ctx=None, target="llvm"):
 
     target : :py:class:`tvm.Target`
         The corresponding context
+
+    Returns
+    -------
+    executor : :py:class:`~tvm.relay.backend.interpreter.Executor`
     """
     if mod is None:
         mod = IRModule()

python/tvm/relay/op/contrib/arm_compute_lib.py

@@ -16,8 +16,8 @@
 # under the License.
 # pylint: disable=invalid-name, unused-argument
 """Arm Compute Library supported operators."""
-import tvm
 import numpy as np
+import tvm
 
 from tvm.relay.expr import const
 from tvm.relay import transform

src/target/llvm/llvm_module.cc

@@ -215,7 +215,8 @@ class LLVMModuleNode final : public runtime::ModuleNode {
         found_linked_params = true;
         continue;
       }
-      ICHECK(kv.second->IsInstance<PrimFuncNode>()) << "Can only lower IR Module with PrimFuncs";
+      ICHECK(kv.second->IsInstance<PrimFuncNode>())
+          << "Can only lower IR Module with PrimFuncs, but got " << kv.second->GetTypeKey();
       auto f = Downcast<PrimFunc>(kv.second);
       if (f->HasNonzeroAttr(tir::attr::kIsEntryFunc)) {
         auto global_symbol = f->GetAttr<String>(tvm::attr::kGlobalSymbol);

src/tir/transforms/arg_binder.cc

@@ -42,7 +42,7 @@ void BinderAddAssert(arith::Analyzer* ana, PrimExpr cond, const std::string& arg
   }
   if (!is_one(scond)) {
     std::ostringstream os;
-    os << "Argument " << arg_name << " has an unsatisfied constraint";
+    os << "Argument " << arg_name << " has an unsatisfied constraint: " << cond;
     asserts->emplace_back(AssertStmt(scond, tvm::tir::StringImm(os.str()), Evaluate(0)));
   }
 }

src/tir/transforms/storage_rewrite.cc

@@ -86,7 +86,9 @@ class LinearAccessPatternFinder final : public StmtExprVisitor {
     size_t level = scope_.size();
     const VarNode* buf = op->buffer_var.get();
     auto it = alloc_info_.find(buf);
-    ICHECK(it != alloc_info_.end());
+    ICHECK(it != alloc_info_.end()) << "Could not find buffer `" << buf->name_hint
+                                    << "` in the list of allocated buffers. Perhaps you are "
+                                       "missing a storage_scope attr for this buffer.";
     ICHECK(it->second.alloc == nullptr);
     it->second.alloc = op;
     it->second.level = level;