Make functions cloneable for testing.

It's not super fast to clone a function, but it is faster than
re-parsing the test case file it came from.

Some tests want to mutate the function, and there may be other tests in
the same script that need the original function.

src/libcretonne/ir/instructions.rs

@@ -93,7 +93,7 @@ impl FromStr for Opcode {
 /// value should have its `ty` field set to `VOID`. The size of `InstructionData` should be kept at
 /// 16 bytes on 64-bit architectures. If more space is needed to represent an instruction, use a
 /// `Box<AuxData>` to store the additional information out of line.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum InstructionData {
     Nullary { opcode: Opcode, ty: Type },
     Unary {
@@ -203,7 +203,7 @@ pub enum InstructionData {
 
 /// A variable list of `Value` operands used for function call arguments and passing arguments to
 /// basic blocks.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct VariableArgs(Vec<Value>);
 
 impl VariableArgs {
@@ -256,7 +256,7 @@ impl Default for VariableArgs {
 
 /// Payload data for jump instructions. These need to carry lists of EBB arguments that won't fit
 /// in the allowed InstructionData size.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct JumpData {
     pub destination: Ebb,
     pub arguments: VariableArgs,
@@ -274,7 +274,7 @@ impl Display for JumpData {
 
 /// Payload data for branch instructions. These need to carry lists of EBB arguments that won't fit
 /// in the allowed InstructionData size.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct BranchData {
     pub arg: Value,
     pub destination: Ebb,
@@ -292,7 +292,7 @@ impl Display for BranchData {
 }
 
 /// Payload of a call instruction.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct CallData {
     /// Second result value for a call producing multiple return values.
     second_result: Value,
@@ -308,7 +308,7 @@ impl Display for CallData {
 }
 
 /// Payload of a return instruction.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct ReturnData {
     // Dynamically sized array containing return values.
     pub args: VariableArgs,