* config/i386/i386.c (assign_386_stack_local): Align DImode slots

[pf3gnuchains/gcc-fork.git] / gcc / config / i386 / i386.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 8ddfa9f..60c000c 100644 (file)
--- a/gcc/config/i386/i386.c
+++ b/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;