ZJIT: Drop PartialEq from FrameState

No one was actually doing equality comparison on `FrameState`s and it
was only derived because `FrameState` was in `ParseError::StackUnderflow`.
No one was reading the `FrameState` out of `StackUnderflow` either.

Save some binary size.

Author: XrXr

zjit/src/hir.rs

@@ -8058,7 +8058,7 @@ impl<'a> std::fmt::Display for FunctionPrinter<'a> {
     }
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone)]
 pub struct FrameState {
     pub iseq: IseqPtr,
     insn_idx: YarvInsnIdx,
@@ -8177,22 +8177,22 @@ impl FrameState {
 
     /// Pop a stack operand
     fn stack_pop(&mut self) -> Result<InsnId, ParseError> {
-        self.stack.pop().ok_or_else(|| ParseError::StackUnderflow(self.clone()))
+        self.stack.pop().ok_or_else(|| ParseError::StackUnderflow(self.insn_idx))
     }
 
     fn stack_pop_n(&mut self, count: usize) -> Result<Vec<InsnId>, ParseError> {
         // Check if we have enough values on the stack
         let stack_len = self.stack.len();
         if stack_len < count {
-            return Err(ParseError::StackUnderflow(self.clone()));
+            return Err(ParseError::StackUnderflow(self.insn_idx));
         }
 
         Ok(self.stack.split_off(stack_len - count))
     }
 
     /// Get a stack-top operand
     fn stack_top(&self) -> Result<InsnId, ParseError> {
-        self.stack.last().ok_or_else(|| ParseError::StackUnderflow(self.clone())).copied()
+        self.stack.last().ok_or_else(|| ParseError::StackUnderflow(self.insn_idx)).copied()
     }
 
     /// Set a stack operand at idx
@@ -8204,9 +8204,9 @@ impl FrameState {
     /// Get a stack operand at idx
     fn stack_topn(&self, idx: usize) -> Result<InsnId, ParseError> {
         let Some(idx) = self.stack.len().checked_sub(idx + 1) else {
-            return Err(ParseError::StackUnderflow(self.clone()));
+            return Err(ParseError::StackUnderflow(self.insn_idx));
         };
-        self.stack.get(idx).ok_or_else(|| ParseError::StackUnderflow(self.clone())).copied()
+        self.stack.get(idx).ok_or_else(|| ParseError::StackUnderflow(self.insn_idx)).copied()
     }
 
     fn setlocal(&mut self, ep_offset: u32, opnd: InsnId) {
@@ -8327,7 +8327,8 @@ pub enum CallType {
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum ParseError {
-    StackUnderflow(FrameState),
+    /// Instruction index of the YARV instruction that underflowed the stack.
+    StackUnderflow(YarvInsnIdx),
     MalformedIseq(u32), // insn_idx into iseq_encoded
     Validation(ValidationError),
     NotAllowed,