Update zjit/src/backend/lir.rs

Co-authored-by: Takashi Kokubun <[email protected]>

Author: tenderlove

zjit/src/backend/lir.rs

@@ -1751,7 +1751,9 @@ impl Assembler
                 self.expand_branch_insn(insn, &mut insns);
             }
 
-            // If the last instruction of the block is a ret, add a pad patch point after it
+            // If the last instruction of the block is a ret, add a pad patch point after it.
+            // Otherwise, because a jump may be longer than a ret, a PatchPoint right before
+            // a ret may overwrite the next block.
             if let Some(last_insn) = block.insns.last() {
                 if matches!(last_insn, Insn::CRet(_)) {
                     insns.push(Insn::PadPatchPoint);