PR target/44132

Emulated TLS rewrite.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@162549 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 802 insertions, 0 deletions

diff --git a/gcc/tree-emutls.c b/gcc/tree-emutls.c
new file mode 100644
index 00000000000..17f97be1104
--- /dev/null
+++ b/gcc/tree-emutls.c
@@ -0,0 +1,802 @@
+/* Lower TLS operations to emulation functions.
+   Copyright (C) 2006, 2007, 2008, 2009, 2010
+   Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 3, or (at your option) any
+later version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "gimple.h"
+#include "tree-pass.h"
+#include "tree-flow.h"
+#include "cgraph.h"
+#include "langhooks.h"
+#include "target.h"
+#include "targhooks.h"
+#include "tree-iterator.h"
+
+
+/* Whenever a target does not support thread-local storage (TLS) natively,
+   we can emulate it with some run-time support in libgcc.  This will in
+   turn rely on "keyed storage" a-la pthread_key_create; essentially all
+   thread libraries provide such functionality.
+
+   In order to coordinate with the libgcc runtime, each TLS variable is
+   described by a "control variable".  This control variable records the
+   required size, alignment, and initial value of the TLS variable for
+   instantiation at runtime.  It also stores an integer token to be used
+   by the runtime to find the address of the variable within each thread.
+
+   On the compiler side, this means that we need to replace all instances
+   of "tls_var" in the code with "*__emutls_get_addr(&control_var)".  We
+   also need to eliminate "tls_var" from the symbol table and introduce
+   "control_var".
+
+   We used to perform all of the transformations during conversion to rtl,
+   and the variable substitutions magically within assemble_variable.
+   However, this late fiddling of the symbol table conflicts with LTO and
+   whole-program compilation.  Therefore we must now make all the changes
+   to the symbol table early in the GIMPLE optimization path, before we
+   write things out to LTO intermediate files.  */
+
+/* These two vectors, once fully populated, are kept in lock-step so that
+   the index of a TLS variable equals the index of its control variable in
+   the other vector.  */
+static varpool_node_set tls_vars;
+static VEC(varpool_node_ptr, heap) *control_vars;
+
+/* For the current basic block, an SSA_NAME that has computed the address 
+   of the TLS variable at the corresponding index.  */
+static VEC(tree, heap) *access_vars;
+
+/* The type of the control structure, shared with the emutls.c runtime.  */
+static tree emutls_object_type;
+
+#if !defined (NO_DOT_IN_LABEL)
+# define EMUTLS_SEPARATOR	"."
+#elif !defined (NO_DOLLAR_IN_LABEL)
+# define EMUTLS_SEPARATOR	"$"
+#else
+# define EMUTLS_SEPARATOR	"_"
+#endif
+
+/* Create an IDENTIFIER_NODE by prefixing PREFIX to the
+   IDENTIFIER_NODE NAME's name.  */
+
+static tree
+prefix_name (const char *prefix, tree name)
+{
+  unsigned plen = strlen (prefix);
+  unsigned nlen = strlen (IDENTIFIER_POINTER (name));
+  char *toname = (char *) alloca (plen + nlen + 1);
+
+  memcpy (toname, prefix, plen);
+  memcpy (toname + plen, IDENTIFIER_POINTER (name), nlen + 1);
+
+  return get_identifier (toname);
+}
+
+/* Create an identifier for the struct __emutls_object, given an identifier
+   of the DECL_ASSEMBLY_NAME of the original object.  */
+
+static tree
+get_emutls_object_name (tree name)
+{
+  const char *prefix = (targetm.emutls.var_prefix
+			? targetm.emutls.var_prefix
+			: "__emutls_v" EMUTLS_SEPARATOR);
+  return prefix_name (prefix, name);
+}
+
+/* Create the fields of the type for the control variables.  Ordinarily
+   this must match struct __emutls_object defined in emutls.c.  However
+   this is a target hook so that VxWorks can define its own layout.  */
+
+tree
+default_emutls_var_fields (tree type, tree *name ATTRIBUTE_UNUSED)
+{
+  tree word_type_node, field, next_field;
+
+  field = build_decl (UNKNOWN_LOCATION,
+		      FIELD_DECL, get_identifier ("__templ"), ptr_type_node);
+  DECL_CONTEXT (field) = type;
+  next_field = field;
+
+  field = build_decl (UNKNOWN_LOCATION,
+		      FIELD_DECL, get_identifier ("__offset"),
+		      ptr_type_node);
+  DECL_CONTEXT (field) = type;
+  DECL_CHAIN (field) = next_field;
+  next_field = field;
+
+  word_type_node = lang_hooks.types.type_for_mode (word_mode, 1);
+  field = build_decl (UNKNOWN_LOCATION,
+		      FIELD_DECL, get_identifier ("__align"),
+		      word_type_node);
+  DECL_CONTEXT (field) = type;
+  DECL_CHAIN (field) = next_field;
+  next_field = field;
+
+  field = build_decl (UNKNOWN_LOCATION,
+		      FIELD_DECL, get_identifier ("__size"), word_type_node);
+  DECL_CONTEXT (field) = type;
+  DECL_CHAIN (field) = next_field;
+
+  return field;
+}
+
+/* Initialize emulated tls object TO, which refers to TLS variable DECL and
+   is initialized by PROXY.  As above, this is the default implementation of
+   a target hook overridden by VxWorks.  */
+
+tree
+default_emutls_var_init (tree to, tree decl, tree proxy)
+{
+  VEC(constructor_elt,gc) *v = VEC_alloc (constructor_elt, gc, 4);
+  constructor_elt *elt;
+  tree type = TREE_TYPE (to);
+  tree field = TYPE_FIELDS (type);
+
+  elt = VEC_quick_push (constructor_elt, v, NULL);
+  elt->index = field;
+  elt->value = fold_convert (TREE_TYPE (field), DECL_SIZE_UNIT (decl));
+
+  elt = VEC_quick_push (constructor_elt, v, NULL);
+  field = DECL_CHAIN (field);
+  elt->index = field;
+  elt->value = build_int_cst (TREE_TYPE (field),
+			      DECL_ALIGN_UNIT (decl));
+
+  elt = VEC_quick_push (constructor_elt, v, NULL);
+  field = DECL_CHAIN (field);
+  elt->index = field;
+  elt->value = null_pointer_node;
+
+  elt = VEC_quick_push (constructor_elt, v, NULL);
+  field = DECL_CHAIN (field);
+  elt->index = field;
+  elt->value = proxy;
+
+  return build_constructor (type, v);
+}
+
+/* Create the structure for struct __emutls_object.  This should match the
+   structure at the top of emutls.c, modulo the union there.  */
+
+static tree
+get_emutls_object_type (void)
+{
+  tree type, type_name, field;
+
+  type = emutls_object_type;
+  if (type)
+    return type;
+
+  emutls_object_type = type = lang_hooks.types.make_type (RECORD_TYPE);
+  type_name = NULL;
+  field = targetm.emutls.var_fields (type, &type_name);
+  if (!type_name)
+    type_name = get_identifier ("__emutls_object");
+  type_name = build_decl (UNKNOWN_LOCATION,
+			  TYPE_DECL, type_name, type);
+  TYPE_NAME (type) = type_name;
+  TYPE_FIELDS (type) = field;
+  layout_type (type);
+
+  return type;
+}
+
+/* Create a read-only variable like DECL, with the same DECL_INITIAL.
+   This will be used for initializing the emulated tls data area.  */
+
+static tree
+get_emutls_init_templ_addr (tree decl)
+{
+  tree name, to;
+
+  if (targetm.emutls.register_common && !DECL_INITIAL (decl)
+      && !DECL_SECTION_NAME (decl))
+    return null_pointer_node;
+
+  name = DECL_ASSEMBLER_NAME (decl);
+  if (!targetm.emutls.tmpl_prefix || targetm.emutls.tmpl_prefix[0])
+    {
+      const char *prefix = (targetm.emutls.tmpl_prefix
+			    ? targetm.emutls.tmpl_prefix
+			    : "__emutls_t" EMUTLS_SEPARATOR);
+      name = prefix_name (prefix, name);
+    }
+
+  to = build_decl (DECL_SOURCE_LOCATION (decl),
+		   VAR_DECL, name, TREE_TYPE (decl));
+  SET_DECL_ASSEMBLER_NAME (to, DECL_NAME (to));
+
+  DECL_ARTIFICIAL (to) = 1;
+  TREE_USED (to) = TREE_USED (decl);
+  TREE_READONLY (to) = 1;
+  DECL_IGNORED_P (to) = 1;
+  DECL_CONTEXT (to) = DECL_CONTEXT (decl);
+  DECL_SECTION_NAME (to) = DECL_SECTION_NAME (decl);
+  DECL_PRESERVE_P (to) = DECL_PRESERVE_P (decl);
+
+  DECL_WEAK (to) = DECL_WEAK (decl);
+  if (DECL_ONE_ONLY (decl))
+    {
+      make_decl_one_only (to, DECL_ASSEMBLER_NAME (to));
+      TREE_STATIC (to) = TREE_STATIC (decl);
+      TREE_PUBLIC (to) = TREE_PUBLIC (decl);
+      DECL_VISIBILITY (to) = DECL_VISIBILITY (decl);
+    }
+  else
+    TREE_STATIC (to) = 1;
+
+  DECL_VISIBILITY_SPECIFIED (to) = DECL_VISIBILITY_SPECIFIED (decl);
+  DECL_INITIAL (to) = DECL_INITIAL (decl);
+  DECL_INITIAL (decl) = NULL;
+
+  if (targetm.emutls.tmpl_section)
+    {
+      DECL_SECTION_NAME (to)
+        = build_string (strlen (targetm.emutls.tmpl_section),
+			targetm.emutls.tmpl_section);
+    }
+
+  varpool_finalize_decl (to);
+  return build_fold_addr_expr (to);
+}
+
+/* Create and return the control variable for the TLS variable DECL.  */
+
+static tree
+new_emutls_decl (tree decl)
+{
+  tree name, to;
+
+  name = DECL_ASSEMBLER_NAME (decl);
+  to = build_decl (DECL_SOURCE_LOCATION (decl), VAR_DECL,
+                   get_emutls_object_name (name),
+                   get_emutls_object_type ());
+
+  SET_DECL_ASSEMBLER_NAME (to, DECL_NAME (to));
+
+  DECL_TLS_MODEL (to) = TLS_MODEL_EMULATED;
+  DECL_ARTIFICIAL (to) = 1;
+  DECL_IGNORED_P (to) = 1;
+  TREE_READONLY (to) = 0;
+  TREE_STATIC (to) = 1;
+
+  DECL_PRESERVE_P (to) = DECL_PRESERVE_P (decl);
+  DECL_CONTEXT (to) = DECL_CONTEXT (decl);
+  TREE_USED (to) = TREE_USED (decl);
+  TREE_PUBLIC (to) = TREE_PUBLIC (decl);
+  DECL_EXTERNAL (to) = DECL_EXTERNAL (decl);
+  DECL_COMMON (to) = DECL_COMMON (decl);
+  DECL_WEAK (to) = DECL_WEAK (decl);
+  DECL_VISIBILITY (to) = DECL_VISIBILITY (decl);
+  DECL_VISIBILITY_SPECIFIED (to) = DECL_VISIBILITY_SPECIFIED (decl);
+  DECL_RESTRICTED_P (to) = DECL_RESTRICTED_P (decl);
+  DECL_DLLIMPORT_P (to) = DECL_DLLIMPORT_P (decl);
+
+  DECL_ATTRIBUTES (to) = targetm.merge_decl_attributes (decl, to);
+
+  if (DECL_ONE_ONLY (decl))
+    make_decl_one_only (to, DECL_ASSEMBLER_NAME (to));
+
+  /* If we're not allowed to change the proxy object's alignment,
+     pretend it has been set by the user.  */
+  if (targetm.emutls.var_align_fixed)
+    DECL_USER_ALIGN (to) = 1;
+
+  /* If the target wants the control variables grouped, do so.  */
+  if (!DECL_COMMON (to) && targetm.emutls.var_section)
+    {
+      DECL_SECTION_NAME (to)
+        = build_string (strlen (targetm.emutls.tmpl_section),
+			targetm.emutls.tmpl_section);
+    }
+
+  /* If this variable is defined locally, then we need to initialize the
+     control structure with size and alignment information.  Initialization
+     of COMMON block variables happens elsewhere via a constructor.  */
+  if (!DECL_EXTERNAL (to)
+      && (!DECL_COMMON (to)
+          || (DECL_INITIAL (decl)
+              && DECL_INITIAL (decl) != error_mark_node)))
+    {
+      tree tmpl = get_emutls_init_templ_addr (decl);
+      DECL_INITIAL (to) = targetm.emutls.var_init (to, decl, tmpl);
+      record_references_in_initializer (to, false);
+    }
+
+  varpool_finalize_decl (to);
+  return to;
+}
+
+/* Look up the index of the TLS variable DECL.  This index can then be
+   used in both the control_vars and access_vars arrays.  */
+
+static unsigned int
+emutls_index (tree decl)
+{
+  varpool_node_set_iterator i;
+  
+  i = varpool_node_set_find (tls_vars, varpool_get_node (decl));
+  gcc_assert (i.index != ~0u);
+
+  return i.index;
+}
+
+/* Look up the control variable for the TLS variable DECL.  */
+
+static tree
+emutls_decl (tree decl)
+{
+  struct varpool_node *var;
+  unsigned int i;
+
+  i = emutls_index (decl);
+  var = VEC_index (varpool_node_ptr, control_vars, i);
+  return var->decl;
+}
+
+/* Generate a call statement to initialize CONTROL_DECL for TLS_DECL.
+   This only needs to happen for TLS COMMON variables; non-COMMON
+   variables can be initialized statically.  Insert the generated
+   call statement at the end of PSTMTS.  */
+   
+static void
+emutls_common_1 (tree tls_decl, tree control_decl, tree *pstmts)
+{
+  tree x;
+  tree word_type_node;
+
+  if (! DECL_COMMON (tls_decl)
+      || (DECL_INITIAL (tls_decl)
+	  && DECL_INITIAL (tls_decl) != error_mark_node))
+    return;
+
+  word_type_node = lang_hooks.types.type_for_mode (word_mode, 1);
+
+  x = build_call_expr (built_in_decls[BUILT_IN_EMUTLS_REGISTER_COMMON], 4,
+		       build_fold_addr_expr (control_decl),
+		       fold_convert (word_type_node,
+				     DECL_SIZE_UNIT (tls_decl)),
+		       build_int_cst (word_type_node,
+				      DECL_ALIGN_UNIT (tls_decl)),
+		       get_emutls_init_templ_addr (tls_decl));
+
+  append_to_statement_list (x, pstmts);
+}
+
+struct lower_emutls_data
+{
+  struct cgraph_node *cfun_node;
+  struct cgraph_node *builtin_node;
+  tree builtin_decl;
+  basic_block bb;
+  int bb_freq;
+  location_t loc;
+  gimple_seq seq;
+};
+
+/* Given a TLS variable DECL, return an SSA_NAME holding its address.
+   Append any new computation statements required to D->SEQ.  */
+
+static tree
+gen_emutls_addr (tree decl, struct lower_emutls_data *d)
+{
+  unsigned int index;
+  tree addr;
+
+  /* Compute the address of the TLS variable with help from runtime.  */
+  index = emutls_index (decl);
+  addr = VEC_index (tree, access_vars, index);
+  if (addr == NULL)
+    {
+      struct varpool_node *cvar;
+      tree cdecl;
+      gimple x;
+
+      cvar = VEC_index (varpool_node_ptr, control_vars, index);
+      cdecl = cvar->decl;
+      TREE_ADDRESSABLE (cdecl) = 1;
+
+      addr = create_tmp_var (build_pointer_type (TREE_TYPE (decl)), NULL);
+      x = gimple_build_call (d->builtin_decl, 1, build_fold_addr_expr (cdecl));
+      gimple_set_location (x, d->loc);
+
+      addr = make_ssa_name (addr, x);
+      gimple_call_set_lhs (x, addr);
+
+      gimple_seq_add_stmt (&d->seq, x);
+
+      cgraph_create_edge (d->cfun_node, d->builtin_node, x,
+                          d->bb->count, d->bb_freq, d->bb->loop_depth);
+
+      /* We may be adding a new reference to a new variable to the function.
+         This means we have to play with the ipa-reference web.  */
+      ipa_record_reference (d->cfun_node, NULL, NULL, cvar, IPA_REF_ADDR, x);
+
+      /* Record this ssa_name for possible use later in the basic block.  */
+      VEC_replace (tree, access_vars, index, addr);
+    }
+
+  return addr;
+}
+
+/* Callback for walk_gimple_op.  D = WI->INFO is a struct lower_emutls_data.
+   Given an operand *PTR within D->STMT, if the operand references a TLS
+   variable, then lower the reference to a call to the runtime.  Insert
+   any new statements required into D->SEQ; the caller is responsible for
+   placing those appropriately.  */
+
+static tree
+lower_emutls_1 (tree *ptr, int *walk_subtrees, void *cb_data)
+{
+  struct walk_stmt_info *wi = (struct walk_stmt_info *) cb_data;
+  struct lower_emutls_data *d = (struct lower_emutls_data *) wi->info;
+  tree t = *ptr;
+  bool is_addr = false;
+  tree addr;
+
+  *walk_subtrees = 0;
+
+  switch (TREE_CODE (t))
+    {
+    case ADDR_EXPR:
+      /* If this is not a straight-forward "&var", but rather something
+	 like "&var.a", then we may need special handling.  */
+      if (TREE_CODE (TREE_OPERAND (t, 0)) != VAR_DECL)
+	{
+	  bool save_changed;
+
+	  /* If we're allowed more than just is_gimple_val, continue.  */
+	  if (!wi->val_only)
+	    {
+	      *walk_subtrees = 1;
+	      return NULL_TREE;
+	    }
+
+	  /* See if any substitution would be made.  */
+	  save_changed = wi->changed;
+	  wi->changed = false;
+	  wi->val_only = false;
+	  walk_tree (&TREE_OPERAND (t, 0), lower_emutls_1, wi, NULL);
+	  wi->val_only = true;
+
+	  /* If so, then extract this entire sub-expression "&p->a" into a
+	     new assignment statement, and substitute yet another SSA_NAME.  */
+	  if (wi->changed)
+	    {
+	      gimple x;
+
+	      addr = create_tmp_var (TREE_TYPE (t), NULL);
+	      x = gimple_build_assign (addr, t);
+	      gimple_set_location (x, d->loc);
+
+	      addr = make_ssa_name (addr, x);
+	      gimple_assign_set_lhs (x, addr);
+
+	      gimple_seq_add_stmt (&d->seq, x);
+
+	      *ptr = addr;
+	    }
+	  else
+	    wi->changed = save_changed;
+
+	  return NULL_TREE;
+	}
+
+      t = TREE_OPERAND (t, 0);
+      is_addr = true;
+      /* FALLTHRU */
+
+    case VAR_DECL:
+      if (!DECL_THREAD_LOCAL_P (t))
+	return NULL_TREE;
+      break;
+
+    default:
+      /* We're not interested in other decls or types, only subexpressions.  */
+      if (EXPR_P (t))
+        *walk_subtrees = 1;
+      /* FALLTHRU */
+
+    case SSA_NAME:
+      /* Special-case the return of SSA_NAME, since it's so common.  */
+      return NULL_TREE;
+    }
+
+  addr = gen_emutls_addr (t, d);
+  if (is_addr)
+    {
+      /* Replace "&var" with "addr" in the statement.  */
+      *ptr = addr;
+    }
+  else
+    {
+      /* Replace "var" with "*addr" in the statement.  */
+      t = build2 (MEM_REF, TREE_TYPE (t), addr,
+	          build_int_cst (TREE_TYPE (addr), 0));
+      *ptr = t;
+    }
+
+  wi->changed = true;
+  return NULL_TREE;
+}
+
+/* Lower all of the operands of STMT.  */
+
+static void
+lower_emutls_stmt (gimple stmt, struct lower_emutls_data *d)
+{
+  struct walk_stmt_info wi;
+
+  d->loc = gimple_location (stmt);
+
+  memset (&wi, 0, sizeof (wi));
+  wi.info = d;
+  wi.val_only = true;
+  walk_gimple_op (stmt, lower_emutls_1, &wi);
+
+  if (wi.changed)
+    update_stmt (stmt);
+}
+
+/* Lower the I'th operand of PHI.  */
+
+static void
+lower_emutls_phi_arg (gimple phi, unsigned int i, struct lower_emutls_data *d)
+{
+  struct walk_stmt_info wi;
+  struct phi_arg_d *pd = gimple_phi_arg (phi, i);
+
+  /* Early out for a very common case we don't care about.  */
+  if (TREE_CODE (pd->def) == SSA_NAME)
+    return;
+
+  d->loc = pd->locus;
+
+  memset (&wi, 0, sizeof (wi));
+  wi.info = d;
+  wi.val_only = true;
+  walk_tree (&pd->def, lower_emutls_1, &wi, NULL);
+
+  /* For normal statements, we let update_stmt do its job.  But for phi
+     nodes, we have to manipulate the immediate use list by hand.  */
+  if (wi.changed)
+    {
+      gcc_assert (TREE_CODE (pd->def) == SSA_NAME);
+      link_imm_use_stmt (&pd->imm_use, pd->def, phi);
+    }
+}
+
+/* Clear the ACCESS_VARS array, in order to begin a new block.  */
+
+static inline void
+clear_access_vars (void)
+{
+  memset (VEC_address (tree, access_vars), 0,
+          VEC_length (tree, access_vars) * sizeof(tree));
+}
+
+/* Lower the entire function NODE.  */
+
+static void
+lower_emutls_function_body (struct cgraph_node *node)
+{
+  struct lower_emutls_data d;
+  bool any_edge_inserts = false;
+
+  current_function_decl = node->decl;
+  push_cfun (DECL_STRUCT_FUNCTION (node->decl));
+
+  d.cfun_node = node;
+  d.builtin_decl = built_in_decls[BUILT_IN_EMUTLS_GET_ADDRESS];
+  d.builtin_node = cgraph_node (d.builtin_decl);
+
+  FOR_EACH_BB (d.bb)
+    {
+      gimple_stmt_iterator gsi;
+      unsigned int i, nedge;
+
+      /* Lower each of the PHI nodes of the block, as we may have 
+	 propagated &tlsvar into a PHI argument.  These loops are
+	 arranged so that we process each edge at once, and each
+	 PHI argument for that edge.  */
+      if (!gimple_seq_empty_p (phi_nodes (d.bb)))
+	{
+	  /* The calls will be inserted on the edges, and the frequencies
+	     will be computed during the commit process.  */
+	  d.bb_freq = 0;
+
+	  nedge = EDGE_COUNT (d.bb->preds);
+	  for (i = 0; i < nedge; ++i)
+	    {
+	      edge e = EDGE_PRED (d.bb, i);
+
+	      /* We can re-use any SSA_NAME created on this edge.  */
+	      clear_access_vars ();
+	      d.seq = NULL;
+
+	      for (gsi = gsi_start_phis (d.bb);
+		   !gsi_end_p (gsi);
+		   gsi_next (&gsi))
+		lower_emutls_phi_arg (gsi_stmt (gsi), i, &d);
+
+	      /* Insert all statements generated by all phi nodes for this
+		 particular edge all at once.  */
+	      if (d.seq)
+		{
+		  gsi_insert_seq_on_edge (e, d.seq);
+		  any_edge_inserts = true;
+		}
+	    }
+	}
+
+      d.bb_freq = compute_call_stmt_bb_frequency (current_function_decl, d.bb);
+
+      /* We can re-use any SSA_NAME created during this basic block.  */
+      clear_access_vars ();
+
+      /* Lower each of the statements of the block.  */
+      for (gsi = gsi_start_bb (d.bb); !gsi_end_p (gsi); gsi_next (&gsi))
+	{
+          d.seq = NULL;
+	  lower_emutls_stmt (gsi_stmt (gsi), &d);
+
+	  /* If any new statements were created, insert them immediately
+	     before the first use.  This prevents variable lifetimes from
+	     becoming unnecessarily long.  */
+	  if (d.seq)
+	    gsi_insert_seq_before (&gsi, d.seq, GSI_SAME_STMT);
+	}
+    }
+
+  if (any_edge_inserts)
+    gsi_commit_edge_inserts ();
+
+  pop_cfun ();
+  current_function_decl = NULL;
+}
+
+/* Main entry point to the tls lowering pass.  */
+
+static unsigned int
+ipa_lower_emutls (void)
+{
+  struct varpool_node *var;
+  struct cgraph_node *func;
+  bool any_aliases = false;
+  tree ctor_body = NULL;
+  unsigned int i, n_tls;
+
+  tls_vars = varpool_node_set_new ();
+
+  /* Examine all global variables for TLS variables.  */
+  for (var = varpool_nodes; var ; var = var->next)
+    if (DECL_THREAD_LOCAL_P (var->decl))
+      {
+	gcc_checking_assert (TREE_STATIC (var->decl)
+			     || DECL_EXTERNAL (var->decl));
+	varpool_node_set_add (tls_vars, var);
+      }
+
+  /* If we found no TLS variables, then there is no further work to do.  */
+  if (tls_vars->nodes == NULL)
+    {
+      tls_vars = NULL;
+      if (dump_file)
+	fprintf (dump_file, "No TLS variables found.\n");
+      return 0;
+    }
+
+  /* Allocate the on-the-side arrays that share indicies with the TLS vars.  */
+  n_tls = VEC_length (varpool_node_ptr, tls_vars->nodes);
+  control_vars = VEC_alloc (varpool_node_ptr, heap, n_tls);
+  access_vars = VEC_alloc (tree, heap, n_tls);
+  VEC_safe_grow (tree, heap, access_vars, n_tls);
+
+  /* Create the control variables for each TLS variable.  */
+  for (i = 0; VEC_iterate (varpool_node_ptr, tls_vars->nodes, i, var); ++i)
+    {
+      tree cdecl;
+      struct varpool_node *cvar;
+
+      var = VEC_index (varpool_node_ptr, tls_vars->nodes, i);
+      cdecl = new_emutls_decl (var->decl);
+
+      cvar = varpool_get_node (cdecl);
+      VEC_quick_push (varpool_node_ptr, control_vars, cvar);
+
+      if (var->alias)
+	{
+	  any_aliases = true;
+	  cvar->alias = true;
+	}
+      else
+	{
+	  /* Make sure the COMMON block control variable gets initialized.
+	     Note that there's no point in doing this for aliases; we only
+	     need to do this once for the main variable.  */
+          emutls_common_1 (var->decl, cdecl, &ctor_body);
+	}
+
+      /* Indicate that the value of the TLS variable may be found elsewhere,
+	 preventing the variable from re-appearing in the GIMPLE.  We cheat
+	 and use the control variable here (rather than a full call_expr),
+	 which is special-cased inside the DWARF2 output routines.  */
+      SET_DECL_VALUE_EXPR (var->decl, cdecl);
+      DECL_HAS_VALUE_EXPR_P (var->decl) = 1;
+    }
+
+  /* If there were any aliases, then frob the alias_pairs vector.  */
+  if (any_aliases)
+    {
+      alias_pair *p;
+      for (i = 0; VEC_iterate (alias_pair, alias_pairs, i, p); ++i)
+	if (DECL_THREAD_LOCAL_P (p->decl))
+	  {
+	    p->decl = emutls_decl (p->decl);
+	    p->target = get_emutls_object_name (p->target);
+	  }
+    }
+
+  /* Adjust all uses of TLS variables within the function bodies.  */
+  for (func = cgraph_nodes; func; func = func->next)
+    if (func->reachable && func->lowered)
+      lower_emutls_function_body (func);
+
+  /* Generate the constructor for any COMMON control variables created.  */
+  if (ctor_body)
+    cgraph_build_static_cdtor ('I', ctor_body, DEFAULT_INIT_PRIORITY);
+
+  VEC_free (varpool_node_ptr, heap, control_vars);
+  VEC_free (tree, heap, access_vars);
+  tls_vars = NULL;
+
+  return TODO_dump_func | TODO_ggc_collect | TODO_verify_all;
+}
+
+/* If the target supports TLS natively, we need do nothing here.  */
+
+static bool
+gate_emutls (void)
+{
+  return !targetm.have_tls;
+}
+
+struct simple_ipa_opt_pass pass_ipa_lower_emutls =
+{
+ {
+  SIMPLE_IPA_PASS,
+  "emutls",				/* name */
+  gate_emutls,				/* gate */
+  ipa_lower_emutls,			/* execute */
+  NULL,                                 /* sub */
+  NULL,                                 /* next */
+  0,                                    /* static_pass_number */
+  TV_NONE,				/* tv_id */
+  PROP_cfg | PROP_ssa,			/* properties_required */
+  0,                                    /* properties_provided */
+  0,                                    /* properties_destroyed */
+  0,                                    /* todo_flags_start */
+  0,					/* todo_flags_finish */
+ }
+};