re PR fortran/44773 (Unnecessary temporaries increase the runtime for channel.f90 by ~70%)

2010-07-10  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/44773
	* trans-expr.c (arrayfunc_assign_needs_temporary): No temporary
	if the lhs has never been host associated, as well as not being
	use associated, a pointer or a target.
	* resolve.c (resolve_variable): Mark variables that are host
	associated.
	* gfortran.h: Add the host_assoc bit to the symbol_attribute
	structure.

From-SVN: r162038

gcc/fortran/ChangeLog

+2010-07-10  Paul Thomas  <pault@gcc.gnu.org>
+
+	PR fortran/44773
+	* trans-expr.c (arrayfunc_assign_needs_temporary): No temporary
+	if the lhs has never been host associated, as well as not being
+	use associated, a pointer or a target.
+	* resolve.c (resolve_variable): Mark variables that are host
+	associated.
+	* gfortran.h: Add the host_assoc bit to the symbol_attribute
+	structure.
+
 2010-07-09  Janus Weil  <janus@gcc.gnu.org>
 
 	* intrinsic.texi: Add documentation for SAME_TYPE_AS, EXTENDS_TYPE_OF,

gcc/fortran/gfortran.h

@@ -682,7 +682,8 @@ typedef struct
     use_assoc:1,		/* Symbol has been use-associated.  */
     use_only:1,			/* Symbol has been use-associated, with ONLY.  */
     use_rename:1,		/* Symbol has been use-associated and renamed.  */
-    imported:1;			/* Symbol has been associated by IMPORT.  */
+    imported:1,			/* Symbol has been associated by IMPORT.  */
+    host_assoc:1;		/* Symbol has been host associated.  */ 
 
   unsigned in_namelist:1, in_common:1, in_equivalence:1;
   unsigned function:1, subroutine:1, procedure:1;

gcc/fortran/resolve.c

@@ -4772,6 +4772,15 @@ resolve_variable (gfc_expr *e)
 	sym->entry_id = current_entry_id + 1;
     }
 
+  /* If a symbol has been host_associated mark it.  This is used latter,
+     to identify if aliasing is possible via host association.  */
+  if (sym->attr.flavor == FL_VARIABLE
+	&& gfc_current_ns->parent
+	&& (gfc_current_ns->parent == sym->ns
+	      || (gfc_current_ns->parent->parent
+		    && gfc_current_ns->parent->parent == sym->ns)))
+    sym->attr.host_assoc = 1;
+
 resolve_procedure:
   if (t == SUCCESS && resolve_procedure_expression (e) == FAILURE)
     t = FAILURE;

gcc/fortran/trans-expr.c

@@ -4978,6 +4978,11 @@ arrayfunc_assign_needs_temporary (gfc_expr * expr1, gfc_expr * expr2)
       if (!expr2->value.function.esym->attr.contained)
 	return false;
 
+      /* A temporary is not needed if the lhs has never been host
+	 associated and the procedure is contained.  */
+      else if (!sym->attr.host_assoc)
+	return false;
+
       /* A temporary is not needed if the variable is local and not
 	 a pointer, a target or a result.  */
       if (sym->ns->parent