Rename subroutine helper (arg to tstring)

When the code generator sets up a call to a precompiled BPF function,
it emits a lot of boilerplate code.  The implementations of DTrace
subroutines typically make such calls.  So there is potential for
much code reuse.

The "path" helper is one such attempt.  Since its usefulness is
broader than just for a "path name" argument, rename this helper to
suggest its broader usage more clearly.

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

libdtrace/dt_cg.c

@@ -3694,24 +3694,27 @@ dt_cg_array_op(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 }
 
 /*
- * This function is a helper function for subroutines that take a path
- * argument and return the tstring resulting from applying a given BPF
- * function (passed by name) on it.
+ * Emit code to call a precompiled BPF function (named by fname)
+ * that is of return type void and takes two arguments:
+ *   - one input value
+ *   - a pointer to an output tstring, allocated here
  */
 static void
-dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
-		       const char *fname)
+dt_cg_subr_arg_to_tstring(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
+			   const char *fname)
 {
 	dt_ident_t	*idp;
-	dt_node_t	*str = dnp->dn_args;
+	dt_node_t	*arg = dnp->dn_args;
 
-	TRACE_REGSET("    subr-path_helper:Begin");
-	dt_cg_node(str, dlp, drp);
-	dt_cg_check_ptr_arg(dlp, drp, str);
+	TRACE_REGSET("    subr-arg_to_tstring:Begin");
 
-	/*
-	 * The result needs to be a temporary string, so we request one.
-	 */
+	/* handle the one "input value" */
+	/* (its type matters only as to whether we check it is null */
+	dt_cg_node(arg, dlp, drp);
+	if (dt_node_is_pointer(arg) || dt_node_is_string(arg))
+		dt_cg_check_ptr_arg(dlp, drp, arg);
+
+	/* allocate the temporary string */
 	dnp->dn_reg = dt_regset_alloc(drp);
 	if (dnp->dn_reg == -1)
 		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
@@ -3724,9 +3727,10 @@ dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
 	if (dt_regset_xalloc_args(drp) == -1)
 		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
 
-	emit(dlp, BPF_MOV_REG(BPF_REG_1, str->dn_reg));
-	dt_regset_free(drp, str->dn_reg);
-	dt_cg_tstring_free(yypcb, str);
+	emit(dlp, BPF_MOV_REG(BPF_REG_1, arg->dn_reg));
+	dt_regset_free(drp, arg->dn_reg);
+	if (dt_node_is_string(arg))
+		dt_cg_tstring_free(yypcb, arg);
 
 	emit(dlp,  BPF_MOV_REG(BPF_REG_2, dnp->dn_reg));
 
@@ -3737,19 +3741,19 @@ dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
 	dt_regset_free_args(drp);
 	dt_regset_free(drp, BPF_REG_0);
 
-	TRACE_REGSET("    subr-path_helper:End  ");
+	TRACE_REGSET("    subr-arg_to_tstring:End  ");
 }
 
 static void
 dt_cg_subr_basename(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 {
-	dt_cg_subr_path_helper(dnp, dlp, drp, "dt_basename");
+	dt_cg_subr_arg_to_tstring(dnp, dlp, drp, "dt_basename");
 }
 
 static void
 dt_cg_subr_dirname(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 {
-	dt_cg_subr_path_helper(dnp, dlp, drp, "dt_dirname");
+	dt_cg_subr_arg_to_tstring(dnp, dlp, drp, "dt_dirname");
 }
 
 static void