Fixed BUG#15737: Stored procedure optimizer bug with LEAVE

  Second version.
  The problem was that the optimizer didn't work correctly with forwards jumps
  to "no-op" hpop and cpop instructions.
  Don't generate "no-op" instructions (hpop 0 and cpop 0), it isn't actually
  necessary.


mysql-test/r/sp-code.result:
  Updated results for new test case (BUG#15737)
mysql-test/t/sp-code.test:
  New test case (BUG#15737)
sql/sp_head.cc:
  Removed backpatch methods from sp_instr_hpop/cpop, since they're not needed any more.
  Added more documentation to sp_head::optimize()
sql/sp_head.h:
  Removed backpatch and opt_mark methods from sp_instr_hpop/cpop, since they're not needed
  any more.
  Added comments to optimizer methods in sp_instr.
sql/sql_yacc.yy:
  Don't generate "no-op" hpop and cpop instructions for LEAVE, it's not necessary.
  Just generate them when needed.

1 files changed, 8 insertions, 9 deletions

diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 0ef389950fc..f41a8b7e979 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -2064,17 +2064,16 @@ sp_proc_stmt:
 	    }
 	    else
 	    {
-	      uint ip= sp->instructions();
 	      sp_instr_jump *i;
-	      sp_instr_hpop *ih;
-	      sp_instr_cpop *ic;
+	      uint ip= sp->instructions();
+	      uint n;
 
-	      ih= new sp_instr_hpop(ip++, ctx, 0);
-	      sp->push_backpatch(ih, lab);
-	      sp->add_instr(ih);
-	      ic= new sp_instr_cpop(ip++, ctx, 0);
-	      sp->push_backpatch(ic, lab);
-	      sp->add_instr(ic);
+	      n= ctx->diff_handlers(lab->ctx);
+	      if (n)
+	        sp->add_instr(new sp_instr_hpop(ip++, ctx, n));
+	      n= ctx->diff_cursors(lab->ctx);
+	      if (n)
+	        sp->add_instr(new sp_instr_cpop(ip++, ctx, n));
 	      i= new sp_instr_jump(ip, ctx);
 	      sp->push_backpatch(i, lab);  /* Jumping forward */
               sp->add_instr(i);