7085 add support for "if" and "else" statements in dtrace

*** 21,32 ****
   * CDDL HEADER END
   *
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  /*
!  * Copyright (c) 2013 by Delphix. All rights reserved.
   * Copyright (c) 2013, Joyent, Inc. All rights reserved.
   */
  
  #include <dt_impl.h>
  
--- 21,33 ----
   * CDDL HEADER END
   *
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
+ 
  /*
!  * Copyright (c) 2014 by Delphix. All rights reserved.
   * Copyright (c) 2013, Joyent, Inc. All rights reserved.
   */
  
  #include <dt_impl.h>
  
*** 153,162 ****
--- 154,165 ----
  %type   <l_node>        probe_definition
  %type   <l_node>        probe_specifiers
  %type   <l_node>        probe_specifier_list
  %type   <l_node>        probe_specifier
  %type   <l_node>        statement_list
+ %type   <l_node>        statement_list_impl
+ %type   <l_node>        statement_or_block
  %type   <l_node>        statement
  %type   <l_node>        declaration
  %type   <l_node>        init_declarator_list
  %type   <l_node>        init_declarator
  
*** 315,335 ****
--- 318,341 ----
                          if (yypcb->pcb_fileptr != NULL) {
                                  dnerror($1, D_SYNTAX, "expected predicate and/"
                                      "or actions following probe description\n");
                          }
                          $$ = dt_node_clause($1, NULL, NULL);
+                         yybegin(YYS_CLAUSE);
                  }
          |       probe_specifiers '{' statement_list '}' {
                          $$ = dt_node_clause($1, NULL, $3);
+                         yybegin(YYS_CLAUSE);
                  }
          |       probe_specifiers DT_TOK_DIV expression DT_TOK_EPRED {
                          dnerror($3, D_SYNTAX, "expected actions { } following "
                              "probe description and predicate\n");
                  }
          |       probe_specifiers DT_TOK_DIV expression DT_TOK_EPRED
                      '{' statement_list '}' {
                          $$ = dt_node_clause($1, $3, $6);
+                         yybegin(YYS_CLAUSE);
                  }
          ;
  
  probe_specifiers:
                  probe_specifier_list { yybegin(YYS_EXPR); $$ = $1; }
*** 345,362 ****
  probe_specifier:
                  DT_TOK_PSPEC { $$ = dt_node_pdesc_by_name($1); }
          |       DT_TOK_INT   { $$ = dt_node_pdesc_by_id($1); }
          ;
  
! statement_list: statement { $$ = $1; }
!         |       statement_list ';' statement { $$ = LINK($1, $3); }
          ;
  
! statement:      /* empty */ { $$ = NULL; }
!         |       expression { $$ = dt_node_statement($1); }
          ;
  
  argument_expression_list:
                  assignment_expression
          |       argument_expression_list DT_TOK_COMMA assignment_expression {
                          $$ = LINK($1, $3);
                  }
--- 351,386 ----
  probe_specifier:
                  DT_TOK_PSPEC { $$ = dt_node_pdesc_by_name($1); }
          |       DT_TOK_INT   { $$ = dt_node_pdesc_by_id($1); }
          ;
  
! statement_list_impl: /* empty */ { $$ = NULL; }
!         |       statement_list_impl statement { $$ = LINK($1, $2); }
          ;
  
! statement_list:
!                 statement_list_impl { $$ = $1; }
!         |       statement_list_impl expression {
!                         $$ = LINK($1, dt_node_statement($2));
!                 }
          ;
  
+ statement_or_block:
+                 statement
+         |       '{' statement_list '}' { $$ = $2; }
+ 
+ statement:      ';' { $$ = NULL; }
+         |       expression ';' { $$ = dt_node_statement($1); }
+         |       DT_KEY_IF DT_TOK_LPAR expression DT_TOK_RPAR statement_or_block {
+                         $$ = dt_node_if($3, $5, NULL);
+                 }
+         |       DT_KEY_IF DT_TOK_LPAR expression DT_TOK_RPAR
+                 statement_or_block DT_KEY_ELSE statement_or_block {
+                         $$ = dt_node_if($3, $5, $7);
+                 }
+         ;
+ 
  argument_expression_list:
                  assignment_expression
          |       argument_expression_list DT_TOK_COMMA assignment_expression {
                          $$ = LINK($1, $3);
                  }