diff --git a/arnoldc/src/arnold.rs b/arnoldc/src/arnold.rs
index 15eee9b0..e0ae689a 100644
--- a/arnoldc/src/arnold.rs
+++ b/arnoldc/src/arnold.rs
@@ -1,7 +1,6 @@
 use anyhow::Result;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 use xrcf::ir::APInt;
 use xrcf::ir::Attribute;
 use xrcf::ir::Block;
diff --git a/arnoldc/src/arnold_to_mlir.rs b/arnoldc/src/arnold_to_mlir.rs
index 2ccbd6c7..5cb9fee5 100644
--- a/arnoldc/src/arnold_to_mlir.rs
+++ b/arnoldc/src/arnold_to_mlir.rs
@@ -1,7 +1,6 @@
 use crate::arnold;
 use anyhow::Result;
 use std::sync::Arc;
-use std::sync::RwLock;
 use xrcf::convert::apply_rewrites;
 use xrcf::convert::ChangedOp;
 use xrcf::convert::Pass;
diff --git a/arnoldc/src/main.rs b/arnoldc/src/main.rs
index 2722be76..2fe4868e 100644
--- a/arnoldc/src/main.rs
+++ b/arnoldc/src/main.rs
@@ -102,8 +102,7 @@ mod tests {
     use anyhow::Result;
     use indoc::indoc;
     use std::panic::Location;
-    use std::sync::Arc;
-    use std::sync::RwLock;
+
     use xrcf::convert::RewriteResult;
     use xrcf::shared::Shared;
     use xrcf::tester::Tester;
diff --git a/xrcf/src/canonicalize.rs b/xrcf/src/canonicalize.rs
index e4f87782..40155f90 100644
--- a/xrcf/src/canonicalize.rs
+++ b/xrcf/src/canonicalize.rs
@@ -8,8 +8,6 @@ use crate::ir::Users;
 use crate::shared::Shared;
 use crate::shared::SharedExt;
 use anyhow::Result;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 pub struct CanonicalizeOp;
 
diff --git a/xrcf/src/convert/cf_to_llvm.rs b/xrcf/src/convert/cf_to_llvm.rs
index 6d328094..0cd97ec7 100644
--- a/xrcf/src/convert/cf_to_llvm.rs
+++ b/xrcf/src/convert/cf_to_llvm.rs
@@ -9,8 +9,6 @@ use crate::ir::Op;
 use crate::shared::Shared;
 use crate::shared::SharedExt;
 use anyhow::Result;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 struct BranchLowering;
 
diff --git a/xrcf/src/convert/experimental_to_mlir.rs b/xrcf/src/convert/experimental_to_mlir.rs
index 42160bc4..7a9f851c 100644
--- a/xrcf/src/convert/experimental_to_mlir.rs
+++ b/xrcf/src/convert/experimental_to_mlir.rs
@@ -24,7 +24,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use dialect::experimental::PrintfOp;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 struct PrintLowering;
 
diff --git a/xrcf/src/convert/func_to_llvm.rs b/xrcf/src/convert/func_to_llvm.rs
index 627581a8..ef3bffb9 100644
--- a/xrcf/src/convert/func_to_llvm.rs
+++ b/xrcf/src/convert/func_to_llvm.rs
@@ -12,8 +12,6 @@ use crate::ir::Op;
 use crate::shared::Shared;
 use crate::shared::SharedExt;
 use anyhow::Result;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 struct AddLowering;
 
diff --git a/xrcf/src/convert/mlir_to_llvmir.rs b/xrcf/src/convert/mlir_to_llvmir.rs
index e3f984ad..aba843e9 100644
--- a/xrcf/src/convert/mlir_to_llvmir.rs
+++ b/xrcf/src/convert/mlir_to_llvmir.rs
@@ -27,8 +27,6 @@ use crate::shared::Shared;
 use crate::shared::SharedExt;
 use crate::targ3t;
 use anyhow::Result;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 struct AddLowering;
 
diff --git a/xrcf/src/dialect/arith/op.rs b/xrcf/src/dialect/arith/op.rs
index 4dff74ed..6c18bd06 100644
--- a/xrcf/src/dialect/arith/op.rs
+++ b/xrcf/src/dialect/arith/op.rs
@@ -21,7 +21,6 @@ use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 /// The token kind used for variables in this dialect.
 ///
diff --git a/xrcf/src/dialect/experimental/op.rs b/xrcf/src/dialect/experimental/op.rs
index 5a2b1fad..667dccf8 100644
--- a/xrcf/src/dialect/experimental/op.rs
+++ b/xrcf/src/dialect/experimental/op.rs
@@ -15,7 +15,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 const TOKEN_KIND: TokenKind = TokenKind::PercentIdentifier;
 
diff --git a/xrcf/src/dialect/func/op.rs b/xrcf/src/dialect/func/op.rs
index cb9f8395..56f72b10 100644
--- a/xrcf/src/dialect/func/op.rs
+++ b/xrcf/src/dialect/func/op.rs
@@ -19,7 +19,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 const TOKEN_KIND: TokenKind = TokenKind::PercentIdentifier;
 
diff --git a/xrcf/src/dialect/llvm/attribute.rs b/xrcf/src/dialect/llvm/attribute.rs
index 33935d61..5be9661d 100644
--- a/xrcf/src/dialect/llvm/attribute.rs
+++ b/xrcf/src/dialect/llvm/attribute.rs
@@ -6,8 +6,6 @@ use crate::parser::ParserDispatch;
 use crate::shared::Shared;
 use std::fmt::Formatter;
 use std::fmt::Result;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 pub struct LinkageAttr {
     value: String,
diff --git a/xrcf/src/dialect/llvm/op.rs b/xrcf/src/dialect/llvm/op.rs
index 5e412532..80af7b34 100644
--- a/xrcf/src/dialect/llvm/op.rs
+++ b/xrcf/src/dialect/llvm/op.rs
@@ -23,7 +23,6 @@ use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 const TOKEN_KIND: TokenKind = TokenKind::PercentIdentifier;
 
diff --git a/xrcf/src/dialect/llvm/typ.rs b/xrcf/src/dialect/llvm/typ.rs
index effb9115..2d64b73e 100644
--- a/xrcf/src/dialect/llvm/typ.rs
+++ b/xrcf/src/dialect/llvm/typ.rs
@@ -8,8 +8,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 /// Represent an integer type such as i32 or i64.
 ///
diff --git a/xrcf/src/dialect/scf/op.rs b/xrcf/src/dialect/scf/op.rs
index 790e1a10..8b211811 100644
--- a/xrcf/src/dialect/scf/op.rs
+++ b/xrcf/src/dialect/scf/op.rs
@@ -11,8 +11,6 @@ use crate::shared::Shared;
 use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 const TOKEN_KIND: TokenKind = TokenKind::PercentIdentifier;
 
diff --git a/xrcf/src/ir/attribute.rs b/xrcf/src/ir/attribute.rs
index b9585206..23098588 100644
--- a/xrcf/src/ir/attribute.rs
+++ b/xrcf/src/ir/attribute.rs
@@ -16,7 +16,6 @@ use std::collections::HashMap;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 /// Attributes are known-constant values of operations (a variable is not allowed).
 /// Attributes belong to operations and can be used to, for example, specify
diff --git a/xrcf/src/ir/module.rs b/xrcf/src/ir/module.rs
index 4f9d3794..80896175 100644
--- a/xrcf/src/ir/module.rs
+++ b/xrcf/src/ir/module.rs
@@ -12,8 +12,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 // See `include/mlir/IR/BuiltinOps.h` and goto definition of
 // `mlir/IR/BuiltinOps.h.inc`.
diff --git a/xrcf/src/ir/op.rs b/xrcf/src/ir/op.rs
index 78f7bca5..c45a4e0e 100644
--- a/xrcf/src/ir/op.rs
+++ b/xrcf/src/ir/op.rs
@@ -14,7 +14,6 @@ use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 /// A specific operation.
 ///
diff --git a/xrcf/src/ir/op_operand.rs b/xrcf/src/ir/op_operand.rs
index a3bf5cc0..8c8bc17a 100644
--- a/xrcf/src/ir/op_operand.rs
+++ b/xrcf/src/ir/op_operand.rs
@@ -14,7 +14,6 @@ use anyhow::Result;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 pub struct OpOperand {
     value: Shared<Value>,
diff --git a/xrcf/src/ir/operation.rs b/xrcf/src/ir/operation.rs
index 5523bebd..190e9000 100644
--- a/xrcf/src/ir/operation.rs
+++ b/xrcf/src/ir/operation.rs
@@ -23,8 +23,6 @@ use anyhow::Result;
 use std::default::Default;
 use std::fmt::Display;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct OperationName {
diff --git a/xrcf/src/ir/region.rs b/xrcf/src/ir/region.rs
index 04b0e42e..f36aec05 100644
--- a/xrcf/src/ir/region.rs
+++ b/xrcf/src/ir/region.rs
@@ -7,8 +7,6 @@ use crate::shared::Shared;
 use crate::shared::SharedExt;
 use std::fmt::Display;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 /// A list of blocks.
 pub struct Region {
diff --git a/xrcf/src/ir/value.rs b/xrcf/src/ir/value.rs
index 652af9a4..7ec5ea7c 100644
--- a/xrcf/src/ir/value.rs
+++ b/xrcf/src/ir/value.rs
@@ -17,7 +17,6 @@ use crate::shared::SharedExt;
 use anyhow::Result;
 use std::fmt::Display;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 pub enum BlockArgumentName {
     /// Anonymous block arguments are used for functions without an implementation.
diff --git a/xrcf/src/targ3t/llvmir/op.rs b/xrcf/src/targ3t/llvmir/op.rs
index 2939be70..c0fe6103 100644
--- a/xrcf/src/targ3t/llvmir/op.rs
+++ b/xrcf/src/targ3t/llvmir/op.rs
@@ -17,7 +17,6 @@ use crate::shared::SharedExt;
 use std::fmt::Display;
 use std::fmt::Formatter;
 use std::sync::Arc;
-use std::sync::RwLock;
 
 /// Display an operand LLVMIR style (e.g., `i32 8`, `i32 %0`, or `label %exit`).
 fn display_operand(f: &mut Formatter<'_>, operand: &Shared<OpOperand>) -> std::fmt::Result {
diff --git a/xrcf/src/targ3t/llvmir/typ.rs b/xrcf/src/targ3t/llvmir/typ.rs
index 503266f5..90948f6d 100644
--- a/xrcf/src/targ3t/llvmir/typ.rs
+++ b/xrcf/src/targ3t/llvmir/typ.rs
@@ -4,8 +4,6 @@ use crate::shared::Shared;
 use crate::shared::SharedExt;
 use std::fmt::Display;
 use std::fmt::Formatter;
-use std::sync::Arc;
-use std::sync::RwLock;
 
 #[derive(Clone)]
 pub struct ArrayType {
diff --git a/xrcf/src/transform.rs b/xrcf/src/transform.rs
index fe6c43dc..84b2948c 100644
--- a/xrcf/src/transform.rs
+++ b/xrcf/src/transform.rs
@@ -16,8 +16,6 @@ use clap::ArgMatches;
 use std::env::ArgsOs;
 use std::fmt;
 use std::fmt::Display;
-use std::sync::Arc;
-use std::sync::RwLock;
 use tracing::subscriber::SetGlobalDefaultError;
 use tracing::Level;
 use tracing_subscriber;