diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5a5fc837415..2c4b86c99f4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 2011-06-14  Jakub Jelinek  <jakub@redhat.com>
 
+	PR fortran/49103
+	* tree.h (DECL_NONSHAREABLE): Define.
+	(struct tree_decl_common): Change decl_common_unused to
+	decl_nonshareable_flag.
+	* cfgexpand.c (expand_used_vars_for_block, clear_tree_used):
+	Ignore vars with DECL_NONSHAREABLE bit set.
+	* tree-cfg.c (gimple_duplicate_bb): Set DECL_NONSHAREABLE
+	on stores to automatic aggregate vars.
+
 	PR rtl-optimization/49390
 	Revert:
 	2010-06-29  Bernd Schmidt  <bernds@codesourcery.com>
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index b22ba71375f..491c2fc48cc 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1098,7 +1098,9 @@ expand_used_vars_for_block (tree block, bool toplevel)
 
   /* Expand all variables at this level.  */
   for (t = BLOCK_VARS (block); t ; t = DECL_CHAIN (t))
-    if (TREE_USED (t))
+    if (TREE_USED (t)
+        && ((TREE_CODE (t) != VAR_DECL && TREE_CODE (t) != RESULT_DECL)
+	    || !DECL_NONSHAREABLE (t)))
       expand_one_var (t, toplevel, true);
 
   this_sv_num = stack_vars_num;
@@ -1131,6 +1133,8 @@ clear_tree_used (tree block)
 
   for (t = BLOCK_VARS (block); t ; t = DECL_CHAIN (t))
     /* if (!TREE_STATIC (t) && !DECL_EXTERNAL (t)) */
+    if ((TREE_CODE (t) != VAR_DECL && TREE_CODE (t) != RESULT_DECL)
+	|| !DECL_NONSHAREABLE (t))
       TREE_USED (t) = 0;
 
   for (t = BLOCK_SUBBLOCKS (block); t ; t = BLOCK_CHAIN (t))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a61de346908..c450a2231d4 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-06-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR fortran/49103
+	* gfortran.dg/pr49103.f90: New test.
+
 2011-06-14  Tom de Vries  <tom@codesourcery.com>
 
 	PR target/45098
diff --git a/gcc/testsuite/gfortran.dg/pr49103.f90 b/gcc/testsuite/gfortran.dg/pr49103.f90
new file mode 100644
index 00000000000..e744c9bbe7f
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr49103.f90
@@ -0,0 +1,19 @@
+! PR fortran/49103
+! { dg-do run }
+  integer :: a(2), b(2), i, j
+  open (10, status='scratch')
+  do j = 1, 2
+    a = (/ 0, 0 /)
+    b = (/ 1, 1 /)
+    do i = 1, 2
+      write (10, *) a
+      write (10, *) b
+    end do
+  end do
+  rewind (10)
+  do i = 0, 7
+    read (10, *) a
+    if (any (a .ne. mod (i, 2))) call abort
+  end do
+  close (10)
+end
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 85fece45d43..44b5c658374 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -5090,6 +5090,7 @@ gimple_duplicate_bb (basic_block bb)
     {
       def_operand_p def_p;
       ssa_op_iter op_iter;
+      tree lhs;
 
       stmt = gsi_stmt (gsi);
       if (gimple_code (stmt) == GIMPLE_LABEL)
@@ -5103,6 +5104,24 @@ gimple_duplicate_bb (basic_block bb)
       maybe_duplicate_eh_stmt (copy, stmt);
       gimple_duplicate_stmt_histograms (cfun, copy, cfun, stmt);
 
+      /* When copying around a stmt writing into a local non-user
+	 aggregate, make sure it won't share stack slot with other
+	 vars.  */
+      lhs = gimple_get_lhs (stmt);
+      if (lhs && TREE_CODE (lhs) != SSA_NAME)
+	{
+	  tree base = get_base_address (lhs);
+	  if (base
+	      && (TREE_CODE (base) == VAR_DECL
+		  || TREE_CODE (base) == RESULT_DECL)
+	      && DECL_IGNORED_P (base)
+	      && !TREE_STATIC (base)
+	      && !DECL_EXTERNAL (base)
+	      && (TREE_CODE (base) != VAR_DECL
+		  || !DECL_HAS_VALUE_EXPR_P (base)))
+	    DECL_NONSHAREABLE (base) = 1;
+	}
+
       /* Create new names for all the definitions created by COPY and
 	 add replacement mappings for each new name.  */
       FOR_EACH_SSA_DEF_OPERAND (def_p, copy, op_iter, SSA_OP_ALL_DEFS)
diff --git a/gcc/tree.h b/gcc/tree.h
index 30c77d8b8ef..f55574dd5f1 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1398,6 +1398,10 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 #define DECL_READ_P(NODE) \
   (TREE_CHECK2 (NODE, VAR_DECL, PARM_DECL)->decl_common.decl_read_flag)
 
+#define DECL_NONSHAREABLE(NODE) \
+  (TREE_CHECK2 (NODE, VAR_DECL, \
+		RESULT_DECL)->decl_common.decl_nonshareable_flag)
+
 /* In a CALL_EXPR, means that the call is the jump from a thunk to the
    thunked-to function.  */
 #define CALL_FROM_THUNK_P(NODE) (CALL_EXPR_CHECK (NODE)->base.protected_flag)
@@ -2887,8 +2891,9 @@ struct GTY(()) tree_decl_common {
      being set.  */
   unsigned decl_read_flag : 1;
 
-  /* Padding so that 'off_align' can be on a 32-bit boundary.  */
-  unsigned decl_common_unused : 1;
+  /* In VAR_DECL or RESULT_DECL set when significant code movement precludes
+     attempting to share the stack slot with some other variable.  */
+  unsigned decl_nonshareable_flag : 1;
 
   /* DECL_OFFSET_ALIGN, used only for FIELD_DECLs.  */
   unsigned int off_align : 8;