ZJIT: Remove an obsoleted PC guard

A little follow-up on ruby#14653

Now that we don't generate a PC-less side exit at the entry block, we
shouldn't need this guard that was added by ruby#14643.

Author: k0kubun

zjit/src/backend/lir.rs

@@ -1607,12 +1607,9 @@ impl Assembler
                     self.store(Opnd::mem(64, SP, (-local_size_and_idx_to_ep_offset(locals.len(), idx) - 1) * SIZEOF_VALUE_I32), opnd);
                 }
 
-                // Avoid setting cfp->pc when exiting entry_block with optional arguments
-                if !pc.is_null() {
-                    asm_comment!(self, "save cfp->pc");
-                    self.load_into(SCRATCH_OPND, Opnd::const_ptr(pc));
-                    self.store(Opnd::mem(64, CFP, RUBY_OFFSET_CFP_PC), SCRATCH_OPND);
-                }
+                asm_comment!(self, "save cfp->pc");
+                self.load_into(SCRATCH_OPND, Opnd::const_ptr(pc));
+                self.store(Opnd::mem(64, CFP, RUBY_OFFSET_CFP_PC), SCRATCH_OPND);
 
                 asm_comment!(self, "save cfp->sp");
                 self.lea_into(SCRATCH_OPND, Opnd::mem(64, SP, stack.len() as i32 * SIZEOF_VALUE_I32));

zjit/src/hir.rs

@@ -3323,7 +3323,6 @@ pub fn iseq_to_hir(iseq: *const rb_iseq_t) -> Result<Function, ParseError> {
     // optimizing locals in that case because they're shared with other frames.
     let ep_escaped = iseq_escapes_ep(iseq);
 
-
     // Compile an entry_block for the interpreter
     compile_entry_block(&mut fun, &jit_entry_insns);