Cranelift: Derive `Copy` for `InstructionData` (#5043)

* Cranelift: Derive `Copy` for `InstructionData`

And update `clone` calls to be copies.

* Add a test for `InstructionData`'s size

cranelift/codegen/meta/src/gen_inst.rs

@@ -71,17 +71,16 @@ fn gen_formats(formats: &[&InstructionFormat], fmt: &mut Formatter) {
 /// the SSA `Value` arguments.
 fn gen_instruction_data(formats: &[&InstructionFormat], fmt: &mut Formatter) {
     for (name, include_args) in &[("InstructionData", true), ("InstructionImms", false)] {
-        fmt.line("#[derive(Clone, Debug, PartialEq, Hash)]");
+        fmt.line("#[derive(Copy, Clone, Debug, PartialEq, Hash)]");
         if !include_args {
-            // `InstructionImms` gets some extra derives: it acts like
-            // a sort of extended opcode and we want to allow for
-            // hashconsing via Eq. `Copy` also turns out to be useful.
-            fmt.line("#[derive(Copy, Eq)]");
+            // `InstructionImms` gets some extra derives: it acts like a sort of
+            // extended opcode and we want to allow for hashconsing via `Eq`.
+            fmt.line("#[derive(Eq)]");
         }
         fmt.line(r#"#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]"#);
         fmt.line("#[allow(missing_docs)]");
-        // generate `enum InstructionData` or `enum InstructionImms`.
-        // (This comment exists so one can grep for `enum InstructionData`!)
+        // Generate `enum InstructionData` or `enum InstructionImms`. (This
+        // comment exists so one can grep for `enum InstructionData`!)
         fmtln!(fmt, "pub enum {} {{", name);
         fmt.indent(|fmt| {
             for format in formats {

cranelift/codegen/src/ir/function.rs

@@ -386,7 +386,7 @@ impl FunctionStencil {
             .zip(self.dfg.inst_results(src))
             .all(|(a, b)| self.dfg.value_type(*a) == self.dfg.value_type(*b)));
 
-        self.dfg[dst] = self.dfg[src].clone();
+        self.dfg[dst] = self.dfg[src];
         self.layout.remove_inst(src);
     }
 

cranelift/codegen/src/ir/instructions.rs

@@ -755,6 +755,19 @@ mod tests {
     use super::*;
     use alloc::string::ToString;
 
+    #[test]
+    fn inst_data_is_copy() {
+        fn is_copy<T: Copy>() {}
+        is_copy::<InstructionData>();
+    }
+
+    #[test]
+    fn inst_data_size() {
+        // The size of `InstructionData` is performance sensitive, so make sure
+        // we don't regress it unintentionally.
+        assert_eq!(std::mem::size_of::<InstructionData>(), 16);
+    }
+
     #[test]
     fn opcodes() {
         use core::mem;

cranelift/codegen/src/machinst/isle.rs

@@ -226,7 +226,7 @@ macro_rules! isle_lower_prelude_methods {
 
         #[inline]
         fn inst_data(&mut self, inst: Inst) -> InstructionData {
-            self.lower_ctx.dfg()[inst].clone()
+            self.lower_ctx.dfg()[inst]
         }
 
         #[inline]

cranelift/codegen/src/simple_gvn.rs

@@ -115,7 +115,7 @@ pub fn do_simple_gvn(func: &mut Function, domtree: &mut DominatorTree) {
 
             let ctrl_typevar = func.dfg.ctrl_typevar(inst);
             let key = HashKey {
-                inst: func.dfg[inst].clone(),
+                inst: func.dfg[inst],
                 ty: ctrl_typevar,
                 pos: &pos,
             };