i386.c (assign_386_stack_local): Align DImode slots to their natural alignment…

i386.c (assign_386_stack_local): Align DImode slots to their natural alignment to avoid store forwarding stalls.

        * config/i386/i386.c (assign_386_stack_local): Align DImode slots
        to their natural alignment to avoid store forwarding stalls.

From-SVN: r133451

gcc/ChangeLog

+2008-03-22  Uros Bizjak  <ubizjak@gmail.com>
+
+	* config/i386/i386.c (assign_386_stack_local): Align DImode slots
+	to their natural alignment to avoid store forwarding stalls.
+
 2008-03-21  Andrew Pinski  <andrew_pinski@playstation.sony.com>
 
 	PR target/27946

gcc/config/i386/i386.c

@@ -16315,6 +16315,7 @@ rtx
 assign_386_stack_local (enum machine_mode mode, enum ix86_stack_slot n)
 {
   struct stack_local_entry *s;
+  int align;
 
   gcc_assert (n < MAX_386_STACK_LOCALS);
 
@@ -16325,11 +16326,19 @@ assign_386_stack_local (enum machine_mode mode, enum ix86_stack_slot n)
     if (s->mode == mode && s->n == n)
       return copy_rtx (s->rtl);
 
+  /* Align DImode slots to their natural alignment
+     to avoid store forwarding stalls.  */
+  if (mode == DImode
+      && (GET_MODE_BITSIZE (mode) > GET_MODE_ALIGNMENT (mode)))
+    align = GET_MODE_BITSIZE (mode);
+  else
+    align = 0;
+
   s = (struct stack_local_entry *)
     ggc_alloc (sizeof (struct stack_local_entry));
   s->n = n;
   s->mode = mode;
-  s->rtl = assign_stack_local (mode, GET_MODE_SIZE (mode), 0);
+  s->rtl = assign_stack_local (mode, GET_MODE_SIZE (mode), align);
 
   s->next = ix86_stack_locals;
   ix86_stack_locals = s;