Fixed the broken backpatching implementation.

Implemented IF-THEN-ELSE.


sql/sp_head.cc:
  Reimplemented the broken backpatching, so it works for nested constructions and
  IF-THEN-ELSE too.
sql/sp_head.h:
  Reimplemented the broken backpatching, so it works for nested constructions and
  IF-THEN-ELSE too.
sql/sp_pcontext.cc:
  Return the value from push-methods, for convenience.
sql/sp_pcontext.h:
  Return the value from push-methods, for convenience.
sql/sql_yacc.yy:
  Implemented IF-THEN-ELSE.
  Corrected for the new backpatch method.

sql/sp_head.cc

@@ -260,25 +260,32 @@ sp_head::restore_lex(THD *thd)
 }
 
 void
-sp_head::push_backpatch(sp_instr *i)
+sp_head::push_backpatch(sp_instr *i, sp_label_t *lab)
 {
-  (void)m_backpatch.push_front(i);
+  bp_t *bp= (bp_t *)my_malloc(sizeof(bp_t), MYF(MY_WME));
+
+  if (bp)
+  {
+    bp->lab= lab;
+    bp->instr= i;
+    (void)m_backpatch.push_front(bp);
+  }
 }
 
 void
-sp_head::backpatch()
+sp_head::backpatch(sp_label_t *lab)
 {
-  sp_instr *ip;
+  bp_t *bp;
   uint dest= instructions();
-  List_iterator_fast<sp_instr> li(m_backpatch);
+  List_iterator_fast<bp_t> li(m_backpatch);
 
-  while ((ip= li++))
-  {
-    sp_instr_jump *i= static_cast<sp_instr_jump *>(ip);
+  while ((bp= li++))
+    if (bp->lab == lab)
+    {
+      sp_instr_jump *i= static_cast<sp_instr_jump *>(bp->instr);
 
-    i->set_destination(dest);
-  }
-  m_backpatch.empty();
+      i->set_destination(dest);
+    }
 }
 
 

sql/sp_head.h

@@ -24,6 +24,8 @@
 
 #include <stddef.h>
 
+struct sp_label;
+
 class sp_instr;
 
 class sp_head : public Sql_alloc
@@ -72,11 +74,14 @@ class sp_head : public Sql_alloc
   void
   restore_lex(THD *thd);
 
+  // Put the instruction on the backpatch list, associated with the label.
   void
-  push_backpatch(sp_instr *i);
+  push_backpatch(sp_instr *, struct sp_label *);
 
+  // Update all instruction with this label in the backpatch list to
+  // the current position.
   void
-  backpatch();
+  backpatch(struct sp_label *);
 
 private:
 
@@ -85,7 +90,12 @@ class sp_head : public Sql_alloc
   LEX *m_mylex;			// My own lex
   LEX m_lex;			// Temp. store for the other lex
   DYNAMIC_ARRAY m_instr;	// The "instructions"
-  List<sp_instr> m_backpatch;	// Instructions needing backpaching
+  typedef struct
+  {
+    struct sp_label *lab;
+    sp_instr *instr;
+  } bp_t;
+  List<bp_t> m_backpatch;	// Instructions needing backpaching
 
   inline sp_instr *
   get_instr(uint i)

sql/sp_pcontext.cc

@@ -92,7 +92,7 @@ sp_pcontext::push(LEX_STRING *name, enum enum_field_types type,
   }
 }
 
-void
+sp_label_t *
 sp_pcontext::push_label(char *name, uint ip)
 {
   sp_label_t *lab = (sp_label_t *)my_malloc(sizeof(sp_label_t), MYF(MY_WME));
@@ -103,18 +103,21 @@ sp_pcontext::push_label(char *name, uint ip)
     lab->ip= ip;
     m_label.push_front(lab);
   }
+  return lab;
 }
 
-void
+sp_label_t *
 sp_pcontext::push_gen_label(uint ip)
 {
+  sp_label_t *lab= NULL;
   char *s= my_malloc(10, MYF(MY_WME)); // 10=...
 
   if (s)
   {
     sprintf(s, ".%08x", m_genlab++); // ...9+1
-    push_label(s, ip);
+    lab= push_label(s, ip);
   }
+  return lab;
 }
 
 sp_label_t *

sql/sp_pcontext.h

@@ -38,7 +38,7 @@ typedef struct
   my_bool isset;
 } sp_pvar_t;
 
-typedef struct
+typedef struct sp_label
 {
   char *name;
   uint ip;			// Instruction index
@@ -116,10 +116,10 @@ class sp_pcontext : public Sql_alloc
     return m_pvar+i;
   }
 
-  void
+  sp_label_t *
   push_label(char *name, uint ip);
 
-  void
+  sp_label_t *
   push_gen_label(uint ip);
 
   sp_label_t *
@@ -131,10 +131,10 @@ class sp_pcontext : public Sql_alloc
     return m_label.head();
   }
 
-  inline void
+  inline sp_label_t *
   pop_label()
   {
-    m_label.pop();
+    return m_label.pop();
   }
 
 private:

sql/sql_yacc.yy

@@ -1044,25 +1044,25 @@ sp_proc_stmt:
 	    lex->sphead->add_instr(i);
 	    lex->sphead->restore_lex(YYTHD);
           }
-/*	| sp_if
-	| sp_case */
+	| IF sp_if END IF {}
+/*	| sp_case */
 	| sp_labeled_control
 	  {}
 	| { /* Unlabeled controls get a secret label. */
 	    LEX *lex= Lex;
 
-	    Lex->spcont->push_gen_label(lex->sphead->instructions());
+	    lex->spcont->push_gen_label(lex->sphead->instructions());
 	  }
 	  sp_unlabeled_control
 	  {
 	    LEX *lex= Lex;
 
-	    lex->spcont->pop_label();
-	    lex->sphead->backpatch();
+	    lex->sphead->backpatch(lex->spcont->pop_label());
 	  }
 	| LEAVE_SYM IDENT
 	  {
 	    LEX *lex= Lex;
+	    sp_head *sp = lex->sphead;
 	    sp_label_t *lab= lex->spcont->find_label($2.str);
 
 	    if (! lab)
@@ -1072,10 +1072,10 @@ sp_proc_stmt:
 	    }
 	    else
 	    {
-	      sp_instr_jump *i= new sp_instr_jump(lex->sphead->instructions());
+	      sp_instr_jump *i= new sp_instr_jump(sp->instructions());
 
-	      lex->sphead->push_backpatch(i);  /* Jumping forward */
-              lex->sphead->add_instr(i);
+	      sp->push_backpatch(i, lab);  /* Jumping forward */
+              sp->add_instr(i);
 	    }
 	  }
 	| ITERATE_SYM IDENT
@@ -1119,6 +1119,44 @@ sp_proc_stmt:
 	  }
 	;
 
+sp_if:
+	  expr THEN_SYM
+	  {
+	    sp_head *sp= Lex->sphead;
+	    sp_pcontext *ctx= Lex->spcont;
+	    uint ip= sp->instructions();
+	    sp_instr_jump_if_not *i = new sp_instr_jump_if_not(ip, $1);
+
+	    sp->push_backpatch(i, ctx->push_gen_label(0));  /* Forward only */
+            sp->add_instr(i);
+	  }
+	  sp_proc_stmts
+	  {
+	    sp_head *sp= Lex->sphead;
+	    sp_pcontext *ctx= Lex->spcont;
+	    uint ip= sp->instructions();
+	    sp_instr_jump *i = new sp_instr_jump(ip);
+
+	    sp->add_instr(i);
+	    sp->backpatch(ctx->pop_label());
+	    sp->push_backpatch(i, ctx->push_gen_label(0));  /* Forward only */
+	  }
+	  sp_elseifs
+	  {
+	    LEX *lex= Lex;
+	    sp_head *sp= lex->sphead;
+	    sp_pcontext *ctx= lex->spcont;
+
+	    sp->backpatch(ctx->pop_label());
+	  }
+	;
+
+sp_elseifs:
+	  /* Empty */
+	| ELSEIF_SYM sp_if
+	| ELSE sp_proc_stmts
+	;
+
 sp_labeled_control:
 	  IDENT ':'
 	  {
@@ -1131,8 +1169,10 @@ sp_labeled_control:
 	      YYABORT;
 	    }
 	    else
+	    {
 	      lex->spcont->push_label($1.str,
 	                              lex->sphead->instructions());
+	    }
 	  }
 	  sp_unlabeled_control IDENT
 	  {
@@ -1152,7 +1192,7 @@ sp_labeled_control:
 	    else
 	    {
 	      lex->spcont->pop_label();
-	      lex->sphead->backpatch();
+	      lex->sphead->backpatch(lab);
 	    }
 	  }
 	;
@@ -1180,11 +1220,13 @@ sp_unlabeled_control:
 	| WHILE_SYM expr DO_SYM
 	  {
 	    LEX *lex= Lex;
-	    uint ip= lex->sphead->instructions();
+	    sp_head *sp= lex->sphead;
+	    uint ip= sp->instructions();
 	    sp_instr_jump_if_not *i = new sp_instr_jump_if_not(ip, $2);
 
-	    lex->sphead->push_backpatch(i);  /* Jumping forward */
-            lex->sphead->add_instr(i);
+	    /* Jumping forward */
+	    sp->push_backpatch(i, lex->spcont->last_label());
+            sp->add_instr(i);
 	  }
 	  sp_proc_stmts END WHILE_SYM
 	  {