[Lang] Support TensorType for irpass::alg_simp() (#8225)

Issue: #

### Brief Summary

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### <samp>🤖 Generated by Copilot at 411b19e</samp>

Add a template function `get_const_stmt_with_value` to
`taichi/ir/statements.h` that creates IR statements for constants of
different types. This is part of improving matrix support in the IR.

### Walkthrough

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### <samp>🤖 Generated by Copilot at 411b19e</samp>

* Add a new template function `get_const_stmt_with_value` to create
constant statements of different types
([link](https://github.com/taichi-dev/taichi/pull/8225/files?diff=unified&w=0#diff-917d9436dcaafa0f1e41ae9bad90273a303f036f00da94e417788a7fa1dc5260R2021-R2050))

taichi/ir/statements.h

@@ -2033,4 +2033,34 @@ class MatrixInitStmt : public Stmt {
   TI_DEFINE_ACCEPT_AND_CLONE
 };
 
+template <typename T>
+std::vector<std::unique_ptr<Stmt>> get_const_stmt_with_value(DataType dt,
+                                                             T value) {
+  if (dt->is<PrimitiveType>()) {
+    TypedConstant constant(dt, value);
+    auto const_stmt = std::make_unique<ConstStmt>(constant);
+
+    std::vector<std::unique_ptr<Stmt>> ret;
+    ret.push_back(std::move(const_stmt));
+    return ret;
+
+  } else if (dt->is<TensorType>()) {
+    DataType element_dt = dt.get_element_type();
+    std::vector<std::unique_ptr<Stmt>> stmts =
+        get_const_stmt_with_value(element_dt, value);
+
+    Stmt *elem_stmt = stmts.back().get();
+    std::vector<Stmt *> elem_stmts(dt->as<TensorType>()->get_num_elements(),
+                                   elem_stmt);
+
+    auto matrix_init_stmt = std::make_unique<MatrixInitStmt>(elem_stmts);
+    matrix_init_stmt->ret_type = dt;
+
+    stmts.push_back(std::move(matrix_init_stmt));
+    return stmts;
+  } else {
+    TI_NOT_IMPLEMENTED
+  }
+}
+
 }  // namespace taichi::lang