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

*** 19,30 ****
   * CDDL HEADER END
   */
  
  /*
   * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2013, Joyent Inc. All rights reserved.
-  * Copyright (c) 2012 by Delphix. All rights reserved.
   * Copyright 2015 Gary Mills
   */
  
  /*
   * DTrace D Language Compiler
--- 19,30 ----
   * CDDL HEADER END
   */
  
  /*
   * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
   * Copyright (c) 2013, Joyent Inc. All rights reserved.
   * Copyright 2015 Gary Mills
   */
  
  /*
   * DTrace D Language Compiler
*** 117,127 ****
  };
  
  static void *dt_compile(dtrace_hdl_t *, int, dtrace_probespec_t, void *,
      uint_t, int, char *const[], FILE *, const char *);
  
- 
  /*ARGSUSED*/
  static int
  dt_idreset(dt_idhash_t *dhp, dt_ident_t *idp, void *ignored)
  {
          idp->di_flags &= ~(DT_IDFLG_REF | DT_IDFLG_MOD |
--- 117,126 ----
*** 2417,2426 ****
--- 2416,2447 ----
                  xyerror(D_MACRO_UNUSED, "extraneous argument '%s' ($%d is "
                      "not referenced)\n", yypcb->pcb_sargv[argc - 1], argc - 1);
          }
  
          /*
+          * Perform sugar transformations (for "if" / "else") and replace the
+          * existing clause chain with the new one.
+          */
+         if (context == DT_CTX_DPROG) {
+                 dt_node_t *dnp, *next_dnp;
+                 dt_node_t *new_list = NULL;
+ 
+                 for (dnp = yypcb->pcb_root->dn_list;
+                     dnp != NULL; dnp = next_dnp) {
+                         /* remove this node from the list */
+                         next_dnp = dnp->dn_list;
+                         dnp->dn_list = NULL;
+ 
+                         if (dnp->dn_kind == DT_NODE_CLAUSE)
+                                 dnp = dt_compile_sugar(dtp, dnp);
+                         /* append node to the new list */
+                         new_list = dt_node_link(new_list, dnp);
+                 }
+                 yypcb->pcb_root->dn_list = new_list;
+         }
+ 
+         /*
           * If we have successfully created a parse tree for a D program, loop
           * over the clauses and actions and instantiate the corresponding
           * libdtrace program.  If we are parsing a D expression, then we
           * simply run the code generator and assembler on the resulting tree.
           */
*** 2436,2445 ****
--- 2457,2468 ----
                          longjmp(yypcb->pcb_jmpbuf, dtrace_errno(dtp));
  
                  for (; dnp != NULL; dnp = dnp->dn_list) {
                          switch (dnp->dn_kind) {
                          case DT_NODE_CLAUSE:
+                                 if (DT_TREEDUMP_PASS(dtp, 4))
+                                         dt_printd(dnp, stderr, 0);
                                  dt_compile_clause(dtp, dnp);
                                  break;
                          case DT_NODE_XLATOR:
                                  if (dtp->dt_xlatemode == DT_XL_DYNAMIC)
                                          dt_compile_xlator(dnp);