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Out Of SSA Rewrite - New TER implementation


This patch re-implements TER.  The fundamental idea remains the same...
step through the function determining tracking which single use
expressions are currently available for substitution,  and marking them
as replaceable if the use is seen while they are still valid.

The list of "current" values was maintained in a linked list, and the
patch in  http://gcc.gnu.org/ml/gcc-patches/2006-08/msg00896.html
replaced that with a bitmap, which turns out ot be much faster in the
more horrible cases.

On top of that a lot of functions have been renamed to make them
clearer, a long description of what TER does and how is at the top of
the file.  The mechanism for tracking current expressions is different
now as well. This allows TER to get a few cases it couldn't get before,
addressing a couple of open PRs.  Although it shares similar
functionality, this really is a rewrite of TER. 

It has also been moved to its own self contained file, tree-ssa-ter.c.
I'd suggest just reading the file rather than the patch :-)

Bootstrapped and regression tested on i686-pc-linux-gnu.  There is one
additional regression caused by this patch. I will address that efore
checking anything in.

It appears to be a bug in the expansion code.

The testcase is gfortran.fortran-torture/execute/st_function.f90.

TER expands 2 additional expression which it didn't before.

    D.1261 = (char[1:] *) &"0123456789"[1]{lb: 1 sz: 1};
    __builtin_memcpy (&st4.6, D.1261, 4);

now gets expanded to 

  __builtin_memcpy (&st4.6, (char[1:] *) &"0123456789"[1]{lb: 1 sz: 1}, 4);


and

    p1 = (char[1:4] *) &i;
    __builtin_memmove (&p.1, p1, 4);

gets expanded to 

    __builtin_memmove (&p.1, (char[1:4] *) &i, 4);

I haven't investigated which is being handled incorrectly yet, but will
look into it before checking the code in.


Andrew


	* Makefile.in: Add new file tree-ssa-ter.c.
	* tree-outof-ssa.c (struct temp_expr_table_d, new_temp_expr_table, 
	free_temp_expr_table, add_value_to_version_list, 
	add_value_to_partition_list, remove_value_from_partition_list, 
	add_dependence, check_replaceable, finish_expr, mark_replaceable, 
	kill_expr, kill_virtual_exprs, find_replaceable_in_bb, 
	find_replaceable_exprs, dump_replaceable_exprs): Move to tree-ssa-ter.c.
	* tree-ssa-live.h (find_replaceable_exprs, dump_replaceable_exprs): Add
	prototypes.
	* tree-ssa-ter.c: New file.
	(struct value_expr_d): Remove.
	(struct temp_expr_table_d): Rename fields, add explicit vector of
	replaceable expressions instead of sharing. Change value_expr_p's to 
	bitmap.  Delete free_list.
	(new_temp_expr_table): Rename fields, count number of ssa_names in
	each partition.
	(free_temp_expr_table): Rename field, free new fields.
	(new_value_expr, free_value_expr, find_value_in_list, add_value_to_list,
	add_info_to_list, remove_value_from_list): Delete.
	(version_to_be_replaced_p): New. Is an ssa-name replaceable?
	(make_dependent_on_partition): New. Set bit in version list, allocating
	a bitmap if need be.
	(add_to_partition_kill_list): New.  Set bit in the partition list,
	allocating a bitmap if need be.
	(remove_from_partition_kill_list): New.  Remove a bit from the
	partition list, free the bitmap if it is empty.
	(add_dependence): Use renamed field, cleanup. Don't add a dependence
	on partitions with only one member.
	(is_replaceable_p): New.  Split out replaceability check from 
	check_replaceable.
	(process_replaceable): New. Replacement code split from 
	check_replaceable.
	(check_replaceable): Removed.
	(finished_with_expr): Renamed from finish_expr.
	(kill_expr): Use renamed fields. Less parameters.
	(kill_virtual_exprs): Less parameters.
	(mark_replaceable): Use renamed fields.
	(find_replaceable_in_bb): Use renamed fields, cleanup.
	(find_replaceable_exprs): Use renamed routines, cleanup.
	(dump_replaceable_exprs): don;t go past end of ssa_names list.
	(debug_ter): New.  Debug routine to dump state.



	* Makefile.in: Add new file tree-ssa-ter.c.
	* tree-outof-ssa.c (struct temp_expr_table_d, new_temp_expr_table, 
	free_temp_expr_table, add_value_to_version_list, 
	add_value_to_partition_list, remove_value_from_partition_list, 
	add_dependence, check_replaceable, finish_expr, mark_replaceable, 
	kill_expr, kill_virtual_exprs, find_replaceable_in_bb, 
	find_replaceable_exprs, dump_replaceable_exprs): Move to tree-ssa-ter.c.
	* tree-ssa-live.h (find_replaceable_exprs, dump_replaceable_exprs): Add
	prototypes.
	* tree-ssa-ter.c: New file.
	(struct value_expr_d): Remove.
	(struct temp_expr_table_d): Rename fields, add explicit vector of
	replaceable expressions instead of sharing. Change value_expr_p's to 
	bitmap.  Delete free_list.
	(new_temp_expr_table): Rename fields, count number of ssa_names in
	each partition.
	(free_temp_expr_table): Rename field, free new fields.
	(new_value_expr, free_value_expr, find_value_in_list, add_value_to_list,
	add_info_to_list, remove_value_from_list): Delete.
	(version_to_be_replaced_p): New. Is an ssa-name replaceable?
	(make_dependent_on_partition): New. Set bit in version list, allocating
	a bitmap if need be.
	(add_to_partition_kill_list): New.  Set bit in the partition list,
	allocating a bitmap if need be.
	(remove_from_partition_kill_list): New.  Remove a bit from the
	partition list, free the bitmap if it is empty.
	(add_dependence): Use renamed field, cleanup. Don't add a dependence
	on partitions with only one member.
	(is_replaceable_p): New.  Split out replaceability check from 
	check_replaceable.
	(process_replaceable): New. Replacement code split from 
	check_replaceable.
	(check_replaceable): Removed.
	(finished_with_expr): Renamed from finish_expr.
	(kill_expr): Use renamed fields. Less parameters.
	(kill_virtual_exprs): Less parameters.
	(mark_replaceable): Use renamed fields.
	(find_replaceable_in_bb): Use renamed fields, cleanup.
	(find_replaceable_exprs): Use renamed routines, cleanup.
	(dump_replaceable_exprs): don;t go past end of ssa_names list.
	(debug_ter): New.  Debug routine to dump state.



diff -cpN ../../liveentry/gcc/Makefile.in ./Makefile.in
*** ../../liveentry/gcc/Makefile.in	2006-11-06 09:02:36.000000000 -0500
--- ./Makefile.in	2006-11-10 17:46:56.000000000 -0500
*************** C_OBJS = c-lang.o stub-objc.o $(C_AND_OB
*** 975,981 ****
  OBJS-common = \
   double-int.o tree-chrec.o tree-scalar-evolution.o tree-data-ref.o	   \
   tree-cfg.o tree-dfa.o tree-eh.o tree-ssa.o tree-optimize.o tree-gimple.o  \
!  gimplify.o tree-pretty-print.o tree-into-ssa.o				   \
   tree-outof-ssa.o tree-ssa-ccp.o tree-vn.o tree-ssa-uncprop.o		   \
   tree-ssa-dce.o  tree-ssa-copy.o tree-nrv.o tree-ssa-copyrename.o	   \
   tree-ssa-pre.o tree-ssa-live.o tree-ssa-operands.o tree-ssa-alias.o       \
--- 975,981 ----
  OBJS-common = \
   double-int.o tree-chrec.o tree-scalar-evolution.o tree-data-ref.o	   \
   tree-cfg.o tree-dfa.o tree-eh.o tree-ssa.o tree-optimize.o tree-gimple.o  \
!  gimplify.o tree-pretty-print.o tree-into-ssa.o tree-ssa-ter.o		   \
   tree-outof-ssa.o tree-ssa-ccp.o tree-vn.o tree-ssa-uncprop.o		   \
   tree-ssa-dce.o  tree-ssa-copy.o tree-nrv.o tree-ssa-copyrename.o	   \
   tree-ssa-pre.o tree-ssa-live.o tree-ssa-operands.o tree-ssa-alias.o       \
*************** tree-into-ssa.o : tree-into-ssa.c $(TREE
*** 1850,1855 ****
--- 1850,1861 ----
     langhooks.h domwalk.h tree-pass.h $(GGC_H) $(PARAMS_H) $(BASIC_BLOCK_H) \
     bitmap.h $(CFGLOOP_H) $(FLAGS_H) hard-reg-set.h $(HASHTAB_H) \
     $(TREE_GIMPLE_H) $(TREE_INLINE_H) $(VARRAY_H) vecprim.h
+ tree-ssa-ter.o : tree-ssa-ter.c $(TREE_FLOW_H) $(CONFIG_H) $(SYSTEM_H) \
+    $(RTL_H) $(TREE_H) $(TM_P_H) $(EXPR_H) output.h $(DIAGNOSTIC_H) \
+    $(FUNCTION_H) $(TIMEVAR_H) $(TM_H) coretypes.h $(TREE_DUMP_H) \
+    langhooks.h tree-pass.h $(TREE_SSA_LIVE_H) $(BASIC_BLOCK_H) bitmap.h \
+    $(FLAGS_H) $(GGC_H) hard-reg-set.h $(HASHTAB_H) $(TREE_GIMPLE_H) \
+    $(TREE_INLINE_H) $(VARRAY_H) toplev.h vecprim.h
  tree-outof-ssa.o : tree-outof-ssa.c $(TREE_FLOW_H) $(CONFIG_H) $(SYSTEM_H) \
     $(RTL_H) $(TREE_H) $(TM_P_H) $(EXPR_H) output.h $(DIAGNOSTIC_H) \
     $(FUNCTION_H) $(TIMEVAR_H) $(TM_H) coretypes.h $(TREE_DUMP_H) \
diff -cpN ../../liveentry/gcc/ter.change ./ter.change
*** ../../liveentry/gcc/ter.change	1969-12-31 19:00:00.000000000 -0500
--- ./ter.change	2006-11-10 17:03:50.000000000 -0500
***************
*** 0 ****
--- 1,42 ----
+ 
+ 	* tree-outof-ssa.c (struct temp_expr_table_d, new_temp_expr_table, 
+ 	free_temp_expr_table, add_value_to_version_list, 
+ 	add_value_to_partition_list, remove_value_from_partition_list, 
+ 	add_dependence, check_replaceable, finish_expr, mark_replaceable, 
+ 	kill_expr, kill_virtual_exprs, find_replaceable_in_bb, 
+ 	find_replaceable_exprs, dump_replaceable_exprs): Move to tree-ssa-ter.c.
+ 	* tree-ssa-live.h (find_replaceable_exprs, dump_replaceable_exprs): Add
+ 	prototypes.
+ 	* tree-ssa-ter.c: New file.
+ 	(struct value_expr_d): Remove.
+ 	(struct temp_expr_table_d): Rename fields, add explicit vector of
+ 	replaceable expressions instead of sharing. Change value_expr_p's to 
+ 	bitmap.  Delete free_list.
+ 	(new_temp_expr_table): Rename fields, count number of ssa_names in
+ 	each partition.
+ 	(free_temp_expr_table): Rename field, free new fields.
+ 	(new_value_expr, free_value_expr, find_value_in_list, add_value_to_list,
+ 	add_info_to_list, remove_value_from_list): Delete.
+ 	(version_to_be_replaced_p): New. Is an ssa-name replaceable?
+ 	(make_dependent_on_partition): New. Set bit in version list, allocating
+ 	a bitmap if need be.
+ 	(add_to_partition_kill_list): New.  Set bit in the partition list,
+ 	allocating a bitmap if need be.
+ 	(remove_from_partition_kill_list): New.  Remove a bit from the
+ 	partition list, free the bitmap if it is empty.
+ 	(add_dependence): Use renamed field, cleanup. Don't add a dependence
+ 	on partitions with only one member.
+ 	(is_replaceable_p): New.  Split out replaceability check from 
+ 	check_replaceable.
+ 	(process_replaceable): New. Replacement code split from 
+ 	check_replaceable.
+ 	(check_replaceable): Removed.
+ 	(finished_with_expr): Renamed from finish_expr.
+ 	(kill_expr): Use renamed fields. Less parameters.
+ 	(kill_virtual_exprs): Less parameters.
+ 	(mark_replaceable): Use renamed fields.
+ 	(find_replaceable_in_bb): Use renamed fields, cleanup.
+ 	(find_replaceable_exprs): Use renamed routines, cleanup.
+ 	(dump_replaceable_exprs): don;t go past end of ssa_names list.
+ 	(debug_ter): New.  Debug routine to dump state.
+ 
diff -cpN ../../liveentry/gcc/tree-outof-ssa.c ./tree-outof-ssa.c
*** ../../liveentry/gcc/tree-outof-ssa.c	2006-11-10 16:14:50.000000000 -0500
--- ./tree-outof-ssa.c	2006-11-10 16:51:41.000000000 -0500
*************** eliminate_virtual_phis (void)
*** 1121,1729 ****
  }
  
  
- /* Temporary Expression Replacement (TER)
- 
-    Replace SSA version variables during out-of-ssa with their defining
-    expression if there is only one use of the variable.
- 
-    A pass is made through the function, one block at a time.  No cross block
-    information is tracked.
- 
-    Variables which only have one use, and whose defining stmt is considered
-    a replaceable expression (see check_replaceable) are entered into 
-    consideration by adding a list of dependent partitions to the version_info
-    vector for that ssa_name_version.  This information comes from the partition
-    mapping for each USE.  At the same time, the partition_dep_list vector for 
-    these partitions have this version number entered into their lists.
- 
-    When the use of a replaceable ssa_variable is encountered, the dependence
-    list in version_info[] is moved to the "pending_dependence" list in case
-    the current expression is also replaceable. (To be determined later in 
-    processing this stmt.) version_info[] for the version is then updated to 
-    point to the defining stmt and the 'replaceable' bit is set.
- 
-    Any partition which is defined by a statement 'kills' any expression which
-    is dependent on this partition.  Every ssa version in the partitions' 
-    dependence list is removed from future consideration.
- 
-    All virtual references are lumped together.  Any expression which is
-    dependent on any virtual variable (via a VUSE) has a dependence added
-    to the special partition defined by VIRTUAL_PARTITION.
- 
-    Whenever a V_MAY_DEF is seen, all expressions dependent this 
-    VIRTUAL_PARTITION are removed from consideration.
- 
-    At the end of a basic block, all expression are removed from consideration
-    in preparation for the next block.  
-    
-    The end result is a vector over SSA_NAME_VERSION which is passed back to
-    rewrite_out_of_ssa.  As the SSA variables are being rewritten, instead of
-    replacing the SSA_NAME tree element with the partition it was assigned, 
-    it is replaced with the RHS of the defining expression.  */
- 
- 
- /* Dependency list element.  This can contain either a partition index or a
-    version number, depending on which list it is in.  */
- 
- typedef struct value_expr_d 
- {
-   int value;
-   struct value_expr_d *next;
- } *value_expr_p;
- 
- 
- /* Temporary Expression Replacement (TER) table information.  */
- 
- typedef struct temp_expr_table_d 
- {
-   var_map map;
-   void **version_info;
-   bitmap *expr_vars;
-   value_expr_p *partition_dep_list;
-   bitmap replaceable;
-   bool saw_replaceable;
-   int virtual_partition;
-   bitmap partition_in_use;
-   value_expr_p free_list;
-   value_expr_p pending_dependence;
- } *temp_expr_table_p;
- 
- /* Used to indicate a dependency on V_MAY_DEFs.  */
- #define VIRTUAL_PARTITION(table)	(table->virtual_partition)
- 
- static temp_expr_table_p new_temp_expr_table (var_map);
- static tree *free_temp_expr_table (temp_expr_table_p);
- static inline value_expr_p new_value_expr (temp_expr_table_p);
- static inline void free_value_expr (temp_expr_table_p, value_expr_p);
- static inline value_expr_p find_value_in_list (value_expr_p, int, 
- 					       value_expr_p *);
- static inline void add_value_to_list (temp_expr_table_p, value_expr_p *, int);
- static inline void add_info_to_list (temp_expr_table_p, value_expr_p *, 
- 				     value_expr_p);
- static value_expr_p remove_value_from_list (value_expr_p *, int);
- static void add_dependence (temp_expr_table_p, int, tree);
- static bool check_replaceable (temp_expr_table_p, tree);
- static void finish_expr (temp_expr_table_p, int, bool);
- static void mark_replaceable (temp_expr_table_p, tree);
- static inline void kill_expr (temp_expr_table_p, int, bool);
- static inline void kill_virtual_exprs (temp_expr_table_p, bool);
- static void find_replaceable_in_bb (temp_expr_table_p, basic_block);
- static tree *find_replaceable_exprs (var_map);
- static void dump_replaceable_exprs (FILE *, tree *);
- 
- 
- /* Create a new TER table for MAP.  */
- 
- static temp_expr_table_p
- new_temp_expr_table (var_map map)
- {
-   temp_expr_table_p t;
- 
-   t = XNEW (struct temp_expr_table_d);
-   t->map = map;
- 
-   t->version_info = XCNEWVEC (void *, num_ssa_names + 1);
-   t->expr_vars = XCNEWVEC (bitmap, num_ssa_names + 1);
-   t->partition_dep_list = XCNEWVEC (value_expr_p,
-                                     num_var_partitions (map) + 1);
- 
-   t->replaceable = BITMAP_ALLOC (NULL);
-   t->partition_in_use = BITMAP_ALLOC (NULL);
- 
-   t->saw_replaceable = false;
-   t->virtual_partition = num_var_partitions (map);
-   t->free_list = NULL;
-   t->pending_dependence = NULL;
- 
-   return t;
- }
- 
- 
- /* Free TER table T.  If there are valid replacements, return the expression 
-    vector.  */
- 
- static tree *
- free_temp_expr_table (temp_expr_table_p t)
- {
-   value_expr_p p;
-   tree *ret = NULL;
-   unsigned i;
- 
- #ifdef ENABLE_CHECKING
-   unsigned x;
-   for (x = 0; x <= num_var_partitions (t->map); x++)
-     gcc_assert (!t->partition_dep_list[x]);
- #endif
- 
-   while ((p = t->free_list))
-     {
-       t->free_list = p->next;
-       free (p);
-     }
- 
-   BITMAP_FREE (t->partition_in_use);
-   BITMAP_FREE (t->replaceable);
- 
-   for (i = 0; i <= num_ssa_names; i++)
-     if (t->expr_vars[i])
-       BITMAP_FREE (t->expr_vars[i]);
-   free (t->expr_vars);
- 
-   free (t->partition_dep_list);
-   if (t->saw_replaceable)
-     ret = (tree *)t->version_info;
-   else
-     free (t->version_info);
-   
-   free (t);
-   return ret;
- }
- 
- 
- /* Allocate a new value list node. Take it from the free list in TABLE if 
-    possible.  */
- 
- static inline value_expr_p
- new_value_expr (temp_expr_table_p table)
- {
-   value_expr_p p;
-   if (table->free_list)
-     {
-       p = table->free_list;
-       table->free_list = p->next;
-     }
-   else
-     p = (value_expr_p) xmalloc (sizeof (struct value_expr_d));
- 
-   return p;
- }
- 
- 
- /* Add value list node P to the free list in TABLE.  */
- 
- static inline void
- free_value_expr (temp_expr_table_p table, value_expr_p p)
- {
-   p->next = table->free_list;
-   table->free_list = p;
- }
- 
- 
- /* Find VALUE if it's in LIST.  Return a pointer to the list object if found,  
-    else return NULL.  If LAST_PTR is provided, it will point to the previous 
-    item upon return, or NULL if this is the first item in the list.  */
- 
- static inline value_expr_p
- find_value_in_list (value_expr_p list, int value, value_expr_p *last_ptr)
- {
-   value_expr_p curr;
-   value_expr_p last = NULL;
- 
-   for (curr = list; curr; last = curr, curr = curr->next)
-     {
-       if (curr->value == value)
-         break;
-     }
-   if (last_ptr)
-     *last_ptr = last;
-   return curr;
- }
- 
- 
- /* Add VALUE to LIST, if it isn't already present.  TAB is the expression 
-    table */
- 
- static inline void
- add_value_to_list (temp_expr_table_p tab, value_expr_p *list, int value)
- {
-   value_expr_p info;
- 
-   if (!find_value_in_list (*list, value, NULL))
-     {
-       info = new_value_expr (tab);
-       info->value = value;
-       info->next = *list;
-       *list = info;
-     }
- }
- 
- 
- /* Add value node INFO if it's value isn't already in LIST.  Free INFO if
-    it is already in the list. TAB is the expression table.  */
- 
- static inline void
- add_info_to_list (temp_expr_table_p tab, value_expr_p *list, value_expr_p info)
- {
-   if (find_value_in_list (*list, info->value, NULL))
-     free_value_expr (tab, info);
-   else
-     {
-       info->next = *list;
-       *list = info;
-     }
- }
- 
- 
- /* Look for VALUE in LIST.  If found, remove it from the list and return it's 
-    pointer.  */
- 
- static value_expr_p
- remove_value_from_list (value_expr_p *list, int value)
- {
-   value_expr_p info, last;
- 
-   info = find_value_in_list (*list, value, &last);
-   if (!info)
-     return NULL;
-   if (!last)
-     *list = info->next;
-   else
-     last->next = info->next;
-  
-   return info;
- }
- 
- 
- /* Add a dependency between the def of ssa VERSION and VAR.  If VAR is 
-    replaceable by an expression, add a dependence each of the elements of the 
-    expression.  These are contained in the pending list.  TAB is the
-    expression table.  */
- 
- static void
- add_dependence (temp_expr_table_p tab, int version, tree var)
- {
-   int i, x;
-   value_expr_p info;
- 
-   i = SSA_NAME_VERSION (var);
-   if (bitmap_bit_p (tab->replaceable, i))
-     {
-       /* This variable is being substituted, so use whatever dependences
-          were queued up when we marked this as replaceable earlier.  */
-       while ((info = tab->pending_dependence))
-         {
- 	  tab->pending_dependence = info->next;
- 	  /* Get the partition this variable was dependent on. Reuse this
- 	     object to represent the current  expression instead.  */
- 	  x = info->value;
- 	  info->value = version;
- 	  add_info_to_list (tab, &(tab->partition_dep_list[x]), info);
-           add_value_to_list (tab, 
- 			     (value_expr_p *)&(tab->version_info[version]), x);
- 	  bitmap_set_bit (tab->partition_in_use, x);
- 	}
-     }
-   else
-     {
-       i = var_to_partition (tab->map, var);
-       gcc_assert (i != NO_PARTITION);
-       add_value_to_list (tab, &(tab->partition_dep_list[i]), version);
-       add_value_to_list (tab, 
- 			 (value_expr_p *)&(tab->version_info[version]), i);
-       bitmap_set_bit (tab->partition_in_use, i);
-     }
- }
- 
- 
- /* Check if expression STMT is suitable for replacement in table TAB.  If so, 
-    create an expression entry.  Return true if this stmt is replaceable.  */
- 
- static bool
- check_replaceable (temp_expr_table_p tab, tree stmt)
- {
-   tree var, def, basevar;
-   int version;
-   ssa_op_iter iter;
-   tree call_expr;
-   bitmap def_vars, use_vars;
- 
-   if (TREE_CODE (stmt) != MODIFY_EXPR)
-     return false;
-   
-   /* Punt if there is more than 1 def, or more than 1 use.  */
-   def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
-   if (!def)
-     return false;
- 
-   if (num_imm_uses (def) != 1)
-     return false;
- 
-   /* There must be no V_MAY_DEFS or V_MUST_DEFS.  */
-   if (!(ZERO_SSA_OPERANDS (stmt, (SSA_OP_VMAYDEF | SSA_OP_VMUSTDEF))))
-     return false;
- 
-   /* Float expressions must go through memory if float-store is on.  */
-   if (flag_float_store && FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
-     return false;
- 
-   /* Calls to functions with side-effects cannot be replaced.  */
-   if ((call_expr = get_call_expr_in (stmt)) != NULL_TREE)
-     {
-       int call_flags = call_expr_flags (call_expr);
-       if (TREE_SIDE_EFFECTS (call_expr)
- 	  && !(call_flags & (ECF_PURE | ECF_CONST | ECF_NORETURN)))
- 	return false;
-     }
- 
-   version = SSA_NAME_VERSION (def);
-   basevar = SSA_NAME_VAR (def);
-   def_vars = BITMAP_ALLOC (NULL);
-   bitmap_set_bit (def_vars, DECL_UID (basevar));
- 
-   /* Add this expression to the dependency list for each use partition.  */
-   FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
-     {
-       add_dependence (tab, version, var);
- 
-       use_vars = tab->expr_vars[SSA_NAME_VERSION (var)];
-       if (use_vars)
- 	bitmap_ior_into (def_vars, use_vars);
-     }
-   tab->expr_vars[version] = def_vars;
- 
-   /* If there are VUSES, add a dependence on virtual defs.  */
-   if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE))
-     {
-       add_value_to_list (tab, (value_expr_p *)&(tab->version_info[version]), 
- 			 VIRTUAL_PARTITION (tab));
-       add_value_to_list (tab, 
- 			 &(tab->partition_dep_list[VIRTUAL_PARTITION (tab)]), 
- 			 version);
-       bitmap_set_bit (tab->partition_in_use, VIRTUAL_PARTITION (tab));
-     }
- 
-   return true;
- }
- 
- 
- /* This function will remove the expression for VERSION from replacement 
-    consideration.n table TAB  If 'replace' is true, it is marked as 
-    replaceable, otherwise not.  */
- 
- static void
- finish_expr (temp_expr_table_p tab, int version, bool replace)
- {
-   value_expr_p info, tmp;
-   int partition;
- 
-   /* Remove this expression from its dependent lists.  The partition dependence
-      list is retained and transfered later to whomever uses this version.  */
-   for (info = (value_expr_p) tab->version_info[version]; info; info = tmp)
-     {
-       partition = info->value;
-       gcc_assert (tab->partition_dep_list[partition]);
-       tmp = remove_value_from_list (&(tab->partition_dep_list[partition]), 
- 				    version);
-       gcc_assert (tmp);
-       free_value_expr (tab, tmp);
-       /* Only clear the bit when the dependency list is emptied via 
-          a replacement. Otherwise kill_expr will take care of it.  */
-       if (!(tab->partition_dep_list[partition]) && replace)
-         bitmap_clear_bit (tab->partition_in_use, partition);
-       tmp = info->next;
-       if (!replace)
-         free_value_expr (tab, info);
-     }
- 
-   if (replace)
-     {
-       tab->saw_replaceable = true;
-       bitmap_set_bit (tab->replaceable, version);
-     }
-   else
-     {
-       gcc_assert (!bitmap_bit_p (tab->replaceable, version));
-       tab->version_info[version] = NULL;
-     }
- }
- 
- 
- /* Mark the expression associated with VAR as replaceable, and enter
-    the defining stmt into the version_info table TAB.  */
- 
- static void
- mark_replaceable (temp_expr_table_p tab, tree var)
- {
-   value_expr_p info;
-   int version = SSA_NAME_VERSION (var);
-   finish_expr (tab, version, true);
- 
-   /* Move the dependence list to the pending list.  */
-   if (tab->version_info[version])
-     {
-       info = (value_expr_p) tab->version_info[version]; 
-       for ( ; info->next; info = info->next)
- 	continue;
-       info->next = tab->pending_dependence;
-       tab->pending_dependence = (value_expr_p)tab->version_info[version];
-     }
- 
-   tab->version_info[version] = SSA_NAME_DEF_STMT (var);
- }
- 
- 
- /* This function marks any expression in TAB which is dependent on PARTITION
-    as NOT replaceable.  CLEAR_BIT is used to determine whether partition_in_use
-    should have its bit cleared.  Since this routine can be called within an
-    EXECUTE_IF_SET_IN_BITMAP, the bit can't always be cleared.  */
- 
- static inline void
- kill_expr (temp_expr_table_p tab, int partition, bool clear_bit)
- {
-   value_expr_p ptr;
- 
-   /* Mark every active expr dependent on this var as not replaceable.  */
-   while ((ptr = tab->partition_dep_list[partition]) != NULL)
-     finish_expr (tab, ptr->value, false);
- 
-   if (clear_bit)
-     bitmap_clear_bit (tab->partition_in_use, partition);
- }
- 
- 
- /* This function kills all expressions in TAB which are dependent on virtual 
-    DEFs.  CLEAR_BIT determines whether partition_in_use gets cleared.  */
- 
- static inline void
- kill_virtual_exprs (temp_expr_table_p tab, bool clear_bit)
- {
-   kill_expr (tab, VIRTUAL_PARTITION (tab), clear_bit);
- }
- 
- 
- /* This function processes basic block BB, and looks for variables which can
-    be replaced by their expressions.  Results are stored in TAB.  */
- 
- static void
- find_replaceable_in_bb (temp_expr_table_p tab, basic_block bb)
- {
-   block_stmt_iterator bsi;
-   tree stmt, def, use;
-   stmt_ann_t ann;
-   int partition;
-   var_map map = tab->map;
-   value_expr_p p;
-   ssa_op_iter iter;
- 
-   for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
-     {
-       stmt = bsi_stmt (bsi);
-       ann = stmt_ann (stmt);
- 
-       /* Determine if this stmt finishes an existing expression.  */
-       FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
- 	{
- 	  unsigned ver = SSA_NAME_VERSION (use);
- 
- 	  if (tab->version_info[ver])
- 	    {
- 	      bool same_root_var = false;
- 	      ssa_op_iter iter2;
- 	      bitmap vars = tab->expr_vars[ver];
- 
- 	      /* See if the root variables are the same.  If they are, we
- 		 do not want to do the replacement to avoid problems with
- 		 code size, see PR tree-optimization/17549.  */
- 	      FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter2, SSA_OP_DEF)
- 		{
- 		  if (bitmap_bit_p (vars, DECL_UID (SSA_NAME_VAR (def))))
- 		    {
- 		      same_root_var = true;
- 		      break;
- 		    }
- 		}
- 
- 	      /* Mark expression as replaceable unless stmt is volatile
- 		 or DEF sets the same root variable as STMT.  */
- 	      if (!ann->has_volatile_ops && !same_root_var)
- 		mark_replaceable (tab, use);
- 	      else
- 		finish_expr (tab, ver, false);
- 	    }
- 	}
-       
-       /* Next, see if this stmt kills off an active expression.  */
-       FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
- 	{
- 	  partition = var_to_partition (map, def);
- 	  if (partition != NO_PARTITION && tab->partition_dep_list[partition])
- 	    kill_expr (tab, partition, true);
- 	}
- 
-       /* Now see if we are creating a new expression or not.  */
-       if (!ann->has_volatile_ops)
- 	check_replaceable (tab, stmt);
- 
-       /* Free any unused dependency lists.  */
-       while ((p = tab->pending_dependence))
- 	{
- 	  tab->pending_dependence = p->next;
- 	  free_value_expr (tab, p);
- 	}
- 
-       /* A V_{MAY,MUST}_DEF kills any expression using a virtual operand.  */
-       if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS))
-         kill_virtual_exprs (tab, true);
-     }
- }
- 
- 
- /* This function is the driver routine for replacement of temporary expressions
-    in the SSA->normal phase, operating on MAP.  If there are replaceable 
-    expressions, a table is returned which maps SSA versions to the 
-    expressions they should be replaced with.  A NULL_TREE indicates no 
-    replacement should take place.  If there are no replacements at all, 
-    NULL is returned by the function, otherwise an expression vector indexed
-    by SSA_NAME version numbers.  */
- 
- static tree *
- find_replaceable_exprs (var_map map)
- {
-   basic_block bb;
-   unsigned i;
-   temp_expr_table_p table;
-   tree *ret;
- 
-   table = new_temp_expr_table (map);
-   FOR_EACH_BB (bb)
-     {
-       bitmap_iterator bi;
- 
-       find_replaceable_in_bb (table, bb);
-       EXECUTE_IF_SET_IN_BITMAP ((table->partition_in_use), 0, i, bi)
-         {
- 	  kill_expr (table, i, false);
- 	}
-     }
- 
-   ret = free_temp_expr_table (table);
-   return ret;
- }
- 
- 
- /* Dump TER expression table EXPR to file F.  */
- 
- static void
- dump_replaceable_exprs (FILE *f, tree *expr)
- {
-   tree stmt, var;
-   int x;
-   fprintf (f, "\nReplacing Expressions\n");
-   for (x = 0; x < (int)num_ssa_names + 1; x++)
-     if (expr[x])
-       {
-         stmt = expr[x];
- 	var = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
- 	gcc_assert (var != NULL_TREE);
- 	print_generic_expr (f, var, TDF_SLIM);
- 	fprintf (f, " replace with --> ");
- 	print_generic_expr (f, TREE_OPERAND (stmt, 1), TDF_SLIM);
- 	fprintf (f, "\n");
-       }
-   fprintf (f, "\n");
- }
- 
- 
  /* This function will rewrite the current program using the variable mapping
     found in MAP.  If the replacement vector VALUES is provided, any 
     occurrences of partitions with non-null entries in the vector will be 
--- 1121,1126 ----
diff -cpN ../../liveentry/gcc/tree-ssa-live.h ./tree-ssa-live.h
*** ../../liveentry/gcc/tree-ssa-live.h	2006-11-10 16:14:50.000000000 -0500
--- ./tree-ssa-live.h	2006-11-10 16:50:16.000000000 -0500
*************** extern conflict_graph build_tree_conflic
*** 586,590 ****
--- 586,594 ----
  extern void coalesce_tpa_members (tpa_p tpa, conflict_graph graph, var_map map,
  				  coalesce_list_p cl, FILE *);
  
+ /* From tree-ssa-ter.c  */
+ extern tree *find_replaceable_exprs (var_map);
+ extern void dump_replaceable_exprs (FILE *, tree *);
+ 
  
  #endif /* _TREE_SSA_LIVE_H  */
diff -cpN ../../liveentry/gcc/tree-ssa-ter.c ./tree-ssa-ter.c
*** ../../liveentry/gcc/tree-ssa-ter.c	1969-12-31 19:00:00.000000000 -0500
--- ./tree-ssa-ter.c	2006-11-10 16:52:29.000000000 -0500
***************
*** 0 ****
--- 1,746 ----
+ /* Routines for performing Temporary Expression Replacement (TER) in SSA trees.
+    Copyright (C) 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+    Contributed by Andrew MacLeod  <amacleod@redhat.com>
+ 
+ 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 2, 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 COPYING.  If not, write to
+ the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+ Boston, MA 02110-1301, USA.  */
+ 
+ 
+ #include "config.h"
+ #include "system.h"
+ #include "coretypes.h"
+ #include "tm.h"
+ #include "tree.h"
+ #include "flags.h"
+ #include "rtl.h"
+ #include "tm_p.h"
+ #include "ggc.h"
+ #include "langhooks.h"
+ #include "hard-reg-set.h"
+ #include "basic-block.h"
+ #include "output.h"
+ #include "expr.h"
+ #include "function.h"
+ #include "diagnostic.h"
+ #include "bitmap.h"
+ #include "tree-flow.h"
+ #include "tree-gimple.h"
+ #include "tree-inline.h"
+ #include "varray.h"
+ #include "timevar.h"
+ #include "hashtab.h"
+ #include "tree-dump.h"
+ #include "tree-ssa-live.h"
+ #include "tree-pass.h"
+ #include "toplev.h"
+ #include "vecprim.h"
+ 
+ 
+ /* Temporary Expression Replacement (TER)
+ 
+    Replace SSA version variables during out-of-ssa with their defining
+    expression if there is only one use of the variable.  
+ 
+    This pass is required in order for the RTL expansion pass to see larger
+    chunks of code.  This allows it to make better choices on RTL pattern
+    selection.  When expand is rewritten and merged with out-of-ssa, and
+    understands SSA, this should be eliminated.  
+ 
+    A pass is made through the function, one block at a time.  No cross block
+    information is tracked.
+ 
+    Variables which only have one use, and whose defining stmt is considered
+    a replaceable expression (see is_replaceable_p) are tracked to see whether
+    they can be replaced at their use location.  
+    
+    n_12 = C * 10
+    a_2 = b_5 + 6
+    v_9 = a_2 * n_12
+ 
+    if there are the only use of n_12 and a_2, TER will substitute in their
+    expressions in v_9, and end up with:
+ 
+    v_9 = (b_5 + 6) * (C * 10)
+ 
+    which will then have the ssa_name assigned to regular variables, and the
+    resulting code which will be passed ot the expander looks something like:
+ 
+    v = (b + 6) * (C * 10)
+ 
+    
+    This requires ensuring that none of the variables used by the expression 
+    change between the def point and where it is used.  Furthermore, if any 
+    of the ssa_names used in this expression are themselves replaceable, we 
+    have to ensure none of that expressions' arguments change either.  
+    Although SSA_NAMES themselves don't change, this pass is performed after 
+    coalescing has coalesced different SSA_NAMES together, so there could be a 
+    definition of an SSA_NAME which is coalesced with a use that causes a
+    problem.  ie
+    
+    PHI b_5 = <b_8(2), b_14(1)>
+    <...>
+    a_2 = b_5 + 6
+    b_8 = c_4 + 4
+    v_9 = a_2 * n_12
+    <...>
+ 
+    If b_5, b_8 and b_14 are all colaesced together...
+    The expression b_5 + 6 CANNOT replace the use in the statement defining v_9
+    because b_8 is in fact killing the value of b_5 since they share a partition
+    and will be assigned the same memory or regster location.
+    
+    TER implements this but stepping through the instructions in a block and
+    tracking potential expressions for replacement, and the paritions they are
+    dependent on.  Expressions are represented by the SSA_NAME_VERSION of the
+    DEF on the LHS of a MODIFY_EXPR and the expression is the RHS.
+ 
+    When a stmt is determined to be a possible replacement expression, the
+    following steps are taken:
+ 
+    EXPR_DECL_UID bitmap is allocated and set to the base variable UID of the 
+    def and any uses in the expression.  non-NULL means the expression is being 
+    tracked.  The UID's themselves are used to prevent TER substitution into
+    accumulating sequences.
+    ie
+    x = x + y
+    x = x + z
+    x = x + w
+    etc.
+    this can result in very large expressions which don't accomplish anything
+    see PR tree-optimization/17549.  
+ 
+    PARTITION_DEPENDENCIES is another bitmap array, and it has a bit set for any 
+    partition which is used in the expression.  This is primarily used to remove
+    an expression from the partition kill lists when a decision is made whether
+    to replace it or not.  This is indexed by ssa version number as well, and
+    indicates a partition number.  virtual operands are not tracked individually,
+    but they are summarized by an artifical partition called VIRTUAL_PARTITION.
+    This means a MAY or MUST def will kill *ALL* expressions that are dependant
+    on a virtual operand.
+    Note that the EXPR_DECL_UID and this bitmap represent very similar 
+    information, but the info in one is not easy to obtain from the other.
+ 
+    KILL_LIST is yet another bitmap array, this time it is indexed by partition
+    number, and represents a list of active expressions which will will no 
+    longer be valid if a definition into this partition takes place.
+ 
+    PARTITION_IN_USE is simply a bitmap which is used to track which partitions
+    currently have sokmething in their kill list.  This is used at the end of 
+    a block to clear out the KILL_LIST bitmaps at the end of each block.
+ 
+    NEW_REPLACEABLE_DEPENDENCIES is used as a temporary place to store 
+    dependencies which will be reused by the current defintion. ALl the uses
+    on an expression are processed before anything else is done. If a use is
+    determined to be a replaceable expression AND the current stmt is also going
+    to be replaceable, all the dependencies of this replaceable use will be
+    picked up by the current stmt's expression. Rather than recreate them, they
+    are simply copied here and then copied into the new expression when it is
+    processed.
+ 
+    a_2 = b_5 + 6
+    v_8 = a_2 + c_4
+ 
+    a_2's expression 'b_5 + 6' is determined to be replaceable at the use 
+    location. It is dependent on the partition 'b_5' is in. This is cached into
+    the NEW_REPLACEABLE_DEPENDENCIES bitmap. and when v_8 is examined for
+    replaceablility, it is a candidate, and it is dependent on the partition 
+    b_5 is in *NOT* a_2, as well as c_4's partition.
+ 
+    if v_8 is also replaceable:
+ 
+    x_9 = v_8 * 5
+ 
+    x_9 is dependent on partitions b_5, and c_4
+    
+    if a statement is found which has either of those partitions written to 
+    before x_9 is used, then x_9 itself is NOT replaceable.  */
+ 
+ 
+ /* Temporary Expression Replacement (TER) table information.  */
+ 
+ typedef struct temp_expr_table_d 
+ {
+   var_map map;
+   bitmap *partition_dependencies;	/* Partitions expr is dependent on.  */
+   tree *replaceable_expressions;	/* Replacement expression table.  */
+   bitmap *expr_decl_uids;		/* Base uids of exprs.  */
+   bitmap *kill_list;			/* Expr's killed by a partition.  */
+   int virtual_partition;		/* Psuedo partition for virtual ops.  */
+   bitmap partition_in_use;		/* Partitions with kill entires.  */
+   bitmap new_replaceable_dependencies;	/* Holding place for pending dep's.  */
+   int *num_in_part;			/* # of ssa_names in a partition.  */
+ } *temp_expr_table_p;
+ 
+ /* Used to indicate a dependency on V_MAY_DEFs.  */
+ #define VIRTUAL_PARTITION(table)	(table->virtual_partition)
+ 
+ #ifdef ENABLE_CHECKING
+ extern void debug_ter (FILE *, temp_expr_table_p);
+ #endif
+ 
+ 
+ /* Create a new TER table for MAP.  */
+ 
+ static temp_expr_table_p
+ new_temp_expr_table (var_map map)
+ {
+   temp_expr_table_p t;
+   unsigned x;
+ 
+   t = XNEW (struct temp_expr_table_d);
+   t->map = map;
+ 
+   t->partition_dependencies = XCNEWVEC (bitmap, num_ssa_names + 1);
+   t->expr_decl_uids = XCNEWVEC (bitmap, num_ssa_names + 1);
+   t->kill_list = XCNEWVEC (bitmap, num_var_partitions (map) + 1);
+ 
+   t->partition_in_use = BITMAP_ALLOC (NULL);
+ 
+   t->virtual_partition = num_var_partitions (map);
+   t->new_replaceable_dependencies = BITMAP_ALLOC (NULL);
+ 
+   t->replaceable_expressions = NULL;
+   t->num_in_part = XCNEWVEC (int, num_var_partitions (map));
+   for (x = 1; x < num_ssa_names; x++)
+     {
+       int p;
+       tree name = ssa_name (x);
+       if (!name)
+         continue;
+       p = var_to_partition (map, name);
+       if (p != NO_PARTITION)
+         t->num_in_part[p]++;
+     }
+ 
+   return t;
+ }
+ 
+ 
+ /* Free TER table T.  If there are valid replacements, return the expression 
+    vector.  */
+ 
+ static tree *
+ free_temp_expr_table (temp_expr_table_p t)
+ {
+   tree *ret = NULL;
+   unsigned i;
+ 
+ #ifdef ENABLE_CHECKING
+   unsigned x;
+   for (x = 0; x <= num_var_partitions (t->map); x++)
+     gcc_assert (!t->kill_list[x]);
+ #endif
+ 
+   BITMAP_FREE (t->partition_in_use);
+ 
+   for (i = 0; i <= num_ssa_names; i++)
+     if (t->expr_decl_uids[i])
+       BITMAP_FREE (t->expr_decl_uids[i]);
+   free (t->expr_decl_uids);
+ 
+   free (t->kill_list);
+   free (t->partition_dependencies);
+ 
+   if (t->replaceable_expressions)
+     ret = t->replaceable_expressions;
+ 
+   free (t);
+   return ret;
+ }
+ 
+ 
+ /* Return TRUE if VERSION is to be replaced by an expression in TAB.  */
+ 
+ static inline bool
+ version_to_be_replaced_p (temp_expr_table_p tab, int version)
+ {
+   if (!tab->replaceable_expressions)
+     return false;
+   return tab->replaceable_expressions[version] != NULL_TREE;
+ }
+ 
+ 
+ /* Add partition P to the list if partititons VERSION is dependent on.  TAB is 
+    the expression table */
+ 
+ static inline void
+ make_dependent_on_partition (temp_expr_table_p tab, int version, int p)
+ {
+   if (!tab->partition_dependencies[version])
+     tab->partition_dependencies[version] = BITMAP_ALLOC (NULL);
+ 
+   bitmap_set_bit (tab->partition_dependencies[version], p);
+ }
+ 
+ 
+ /* Add VER to the kill list for P.  TAB is the expression table */
+ 
+ static inline void
+ add_to_partition_kill_list (temp_expr_table_p tab, int p, int ver)
+ {
+   if (!tab->kill_list[p])
+     {
+       tab->kill_list[p] = BITMAP_ALLOC (NULL);
+       bitmap_set_bit (tab->partition_in_use, p);
+     }
+   bitmap_set_bit (tab->kill_list[p], ver);
+ }
+ 
+ 
+ /* Remove VER from the partition kill list for P.  TAB is the expression 
+    table.  */
+ 
+ static inline void 
+ remove_from_partition_kill_list (temp_expr_table_p tab, int p, int version)
+ {
+ #ifdef ENABLE_CHECKING
+   gcc_assert (tab->kill_list[p]);
+ #endif
+   bitmap_clear_bit (tab->kill_list[p], version);
+   if (bitmap_empty_p (tab->kill_list[p]))
+     {
+       bitmap_clear_bit (tab->partition_in_use, p);
+       BITMAP_FREE (tab->kill_list[p]);
+     }
+ }
+ 
+ 
+ /* Add a dependency between the def of ssa VERSION and VAR.  If VAR is 
+    replaceable by an expression, add a dependence each of the elements of the 
+    expression.  These are contained in the new_replaceable list.  TAB is the
+    expression table.  */
+ 
+ static void
+ add_dependence (temp_expr_table_p tab, int version, tree var)
+ {
+   int i;
+   bitmap_iterator bi;
+   unsigned x;
+ 
+   i = SSA_NAME_VERSION (var);
+   if (version_to_be_replaced_p (tab, i))
+     {
+       if (!bitmap_empty_p (tab->new_replaceable_dependencies))
+         {
+ 	  /* Version will now be killed by a write to any partition the 
+ 	     substituted expression would have been killed by.  */
+ 	  EXECUTE_IF_SET_IN_BITMAP (tab->new_replaceable_dependencies, 0, x, bi)
+ 	    add_to_partition_kill_list (tab, x, version);
+ 
+ 	  /* Rather than set partition_dependencies and in_use lists bit by 
+ 	     bit, simply OR in the new_replaceable_dependencies bits.  */
+ 	  if (!tab->partition_dependencies[version])
+ 	    tab->partition_dependencies[version] = BITMAP_ALLOC (NULL);
+ 	  bitmap_ior_into (tab->partition_dependencies[version], 
+ 			   tab->new_replaceable_dependencies);
+ 	  bitmap_ior_into (tab->partition_in_use, 
+ 			   tab->new_replaceable_dependencies);
+ 	  /* It is only necessary to add these once.  */
+ 	  bitmap_clear (tab->new_replaceable_dependencies);
+ 	}
+     }
+   else
+     {
+       i = var_to_partition (tab->map, var);
+ #ifdef ENABLE_CHECKING
+       gcc_assert (i != NO_PARTITION);
+       gcc_assert (tab->num_in_part[i] != 0);
+ #endif
+       /* Only dependencies on ssa_names which are coalesced with something need
+          to be tracked.  Partitions with containing only a single SSA_NAME
+ 	 *cannot* have their value changed.  */
+       if (tab->num_in_part[i] > 1)
+         {
+ 	  add_to_partition_kill_list (tab, i, version);
+ 	  make_dependent_on_partition (tab, version, i);
+ 	}
+     }
+ }
+ 
+ 
+ /* Return TRUE if expression STMT is suitable for replacement.  */
+ 
+ static inline bool
+ is_replaceable_p (tree stmt)
+ {
+   tree call_expr;
+   use_operand_p use_p;
+   tree def, use_stmt;
+ 
+   /* Only consider modify stmts.  */
+   if (TREE_CODE (stmt) != MODIFY_EXPR)
+     return false;
+ 
+   /* Punt if there is more than 1 def.  */
+   def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
+   if (!def)
+     return false;
+ 
+   /* Only consider definitions which have a single use.  */
+   if (!single_imm_use (def, &use_p, &use_stmt))
+     return false;
+ 
+   /* If the use isn't in this block, it wont be replaced either.  */
+   if (bb_for_stmt (use_stmt) != bb_for_stmt (stmt))
+     return false;
+ 
+   /* Used in this block, but at the TOP of the block, not the end.  */
+   if (TREE_CODE (use_stmt) == PHI_NODE)
+     return false;
+ 
+   /* There must be no V_MAY_DEFS or V_MUST_DEFS.  */
+   if (!(ZERO_SSA_OPERANDS (stmt, (SSA_OP_VMAYDEF | SSA_OP_VMUSTDEF))))
+     return false;
+ 
+   /* Float expressions must go through memory if float-store is on.  */
+   if (flag_float_store && FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
+     return false;
+ 
+   /* Calls to functions with side-effects cannot be replaced.  */
+   if ((call_expr = get_call_expr_in (stmt)) != NULL_TREE)
+     {
+       int call_flags = call_expr_flags (call_expr);
+       if (TREE_SIDE_EFFECTS (call_expr)
+ 	  && !(call_flags & (ECF_PURE | ECF_CONST | ECF_NORETURN)))
+ 	return false;
+     }
+ 
+   /* Leave any stmt with voltile operands alone as well.  */
+   if (stmt_ann (stmt)->has_volatile_ops)
+     return false;
+   
+ 
+   return true;
+ }
+ 
+ 
+ /* This function will remove the expression for VERSION from replacement 
+    consideration in table TAB.  If FREE_EXPR is true, then remove the 
+    expression from consideration as well by freeing the decl uid bitmap.  */
+ 
+ static void
+ finished_with_expr (temp_expr_table_p tab, int version, bool free_expr)
+ {
+   unsigned i;
+   bitmap_iterator bi;
+ 
+   /* Remove this expression from its dependent lists.  The partition dependence
+      list is retained and transfered later to whomever uses this version.  */
+   if (tab->partition_dependencies[version])
+     {
+       EXECUTE_IF_SET_IN_BITMAP (tab->partition_dependencies[version], 0, i, bi)
+ 	remove_from_partition_kill_list (tab, i, version);
+       BITMAP_FREE (tab->partition_dependencies[version]);
+     }
+   if (free_expr)
+     BITMAP_FREE (tab->expr_decl_uids[version]);
+ }
+ 
+ 
+ /* Create an expression entry fora replaceable expression.  */
+ 
+ static void 
+ process_replaceable (temp_expr_table_p tab, tree stmt)
+ {
+   tree var, def, basevar;
+   int version;
+   ssa_op_iter iter;
+   bitmap def_vars, use_vars;
+ 
+ #ifdef ENABLE_CHECKING
+   gcc_assert (is_replaceable_p (stmt));
+ #endif
+ 
+   def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
+   version = SSA_NAME_VERSION (def);
+   basevar = SSA_NAME_VAR (def);
+   def_vars = BITMAP_ALLOC (NULL);
+ 
+   bitmap_set_bit (def_vars, DECL_UID (basevar));
+ 
+   /* Add this expression to the dependency list for each use partition.  */
+   FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
+     {
+       int var_version = SSA_NAME_VERSION (var);
+ 
+       use_vars = tab->expr_decl_uids[var_version];
+       add_dependence (tab, version, var);
+       if (use_vars)
+         {
+ 	  bitmap_ior_into (def_vars, use_vars);
+ 	  BITMAP_FREE (tab->expr_decl_uids[var_version]);
+ 	}
+       else
+ 	bitmap_set_bit (def_vars, DECL_UID (SSA_NAME_VAR (var)));
+     }
+   tab->expr_decl_uids[version] = def_vars;
+ 
+   /* If there are VUSES, add a dependence on virtual defs.  */
+   if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE))
+     {
+       make_dependent_on_partition (tab, version, VIRTUAL_PARTITION (tab));
+       add_to_partition_kill_list (tab, VIRTUAL_PARTITION (tab), version);
+     }
+ }
+ 
+ 
+ /* This function removes any expression in TAB which is dependent on PARTITION
+    from consideration, making it not replaceable.  */
+ 
+ static inline void
+ kill_expr (temp_expr_table_p tab, int partition)
+ {
+   unsigned version;
+ 
+   /* Mark every active expr dependent on this var as not replaceable.  
+      finished_with_expr can modify the bitmap, so we can't execute over it.  */
+   while (tab->kill_list[partition])
+     {
+       version = bitmap_first_set_bit (tab->kill_list[partition]);
+       finished_with_expr (tab, version, true);
+     }
+ 
+ #ifdef ENABLE_CHECKING
+   gcc_assert (!tab->kill_list[partition]);
+ #endif
+ }
+ 
+ 
+ /* This function kills all expressions in TAB which are dependent on virtual 
+    partitions.  */
+ 
+ static inline void
+ kill_virtual_exprs (temp_expr_table_p tab)
+ {
+   kill_expr (tab, VIRTUAL_PARTITION (tab));
+ }
+ 
+ 
+ /* Mark the expression associated with VAR as replaceable, and enter
+    the defining stmt into the partition_dependencies table TAB.  if
+    MORE_REPLACING is true, accumulate the pending partition dependencies.  */
+ 
+ static void
+ mark_replaceable (temp_expr_table_p tab, tree var, bool more_replacing)
+ {
+   int version = SSA_NAME_VERSION (var);
+ 
+   /* Move the dependence list to the pending listpending.  */
+   if (more_replacing && tab->partition_dependencies[version])
+     bitmap_ior_into (tab->new_replaceable_dependencies, 
+ 		     tab->partition_dependencies[version]);
+ 
+   finished_with_expr (tab, version, !more_replacing);
+ 
+   /* Set the replaceable expression.  */
+   if (!tab->replaceable_expressions)
+     tab->replaceable_expressions = XCNEWVEC (tree, num_ssa_names + 1);
+   tab->replaceable_expressions[version] = SSA_NAME_DEF_STMT (var);
+ }
+ 
+ 
+ /* This function processes basic block BB, and looks for variables which can
+    be replaced by their expressions.  Results are stored in the table TAB.  */
+ 
+ static void
+ find_replaceable_in_bb (temp_expr_table_p tab, basic_block bb)
+ {
+   block_stmt_iterator bsi;
+   tree stmt, def, use;
+   stmt_ann_t ann;
+   int partition;
+   var_map map = tab->map;
+   ssa_op_iter iter;
+   bool stmt_replaceable;
+ 
+   for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+     {
+       stmt = bsi_stmt (bsi);
+       ann = stmt_ann (stmt);
+ 
+       stmt_replaceable = is_replaceable_p (stmt);
+       /* Determine if this stmt finishes an existing expression.  */
+       FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
+ 	{
+ 	  unsigned ver = SSA_NAME_VERSION (use);
+ 
+ 	  /* If this use is a potential replacement variable, process it.  */
+ 	  if (tab->expr_decl_uids[ver])
+ 	    {
+ 	      bool same_root_var = false;
+ 	      ssa_op_iter iter2;
+ 	      bitmap vars = tab->expr_decl_uids[ver];
+ 
+ 	      /* See if the root variables are the same.  If they are, we
+ 		 do not want to do the replacement to avoid problems with
+ 		 code size, see PR tree-optimization/17549.  */
+ 	      if (!bitmap_empty_p (vars))
+ 		FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter2, SSA_OP_DEF)
+ 		  {
+ 		    if (bitmap_bit_p (vars, DECL_UID (SSA_NAME_VAR (def))))
+ 		      {
+ 			same_root_var = true;
+ 			break;
+ 		      }
+ 		  }
+ 
+ 	      /* Mark expression as replaceable unless stmt is volatile or the 
+ 		 def variable has the same root variable as something in the 
+ 		 substitution list.  */
+ 	      if (ann->has_volatile_ops || same_root_var)
+ 		finished_with_expr (tab, ver, true);
+ 	      else
+ 		mark_replaceable (tab, use, stmt_replaceable);
+ 	    }
+ 	}
+       
+       /* Next, see if this stmt kills off an active expression.  */
+       FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
+ 	{
+ 	  partition = var_to_partition (map, def);
+ 	  if (partition != NO_PARTITION && tab->kill_list[partition])
+ 	    kill_expr (tab, partition);
+ 	}
+ 
+       /* Now see if we are creating a new expression or not.  */
+       if (stmt_replaceable)
+ 	process_replaceable (tab, stmt);
+ 
+       /* Free any unused dependency lists.  */
+       bitmap_clear (tab->new_replaceable_dependencies);
+ 
+       /* A V_{MAY,MUST}_DEF kills any expression using a virtual operand,
+ 	 including the current stmt.  */
+       if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS))
+         kill_virtual_exprs (tab);
+     }
+ }
+ 
+ 
+ /* This function is the driver routine for replacement of temporary expressions
+    in the SSA->normal phase, operating on MAP.  If there are replaceable 
+    expressions, a table is returned which maps SSA versions to the 
+    expressions they should be replaced with.  A NULL_TREE indicates no 
+    replacement should take place.  If there are no replacements at all, 
+    NULL is returned by the function, otherwise an expression vector indexed
+    by SSA_NAME version numbers.  */
+ 
+ extern tree *
+ find_replaceable_exprs (var_map map)
+ {
+   basic_block bb;
+   temp_expr_table_p table;
+   tree *ret;
+ 
+   table = new_temp_expr_table (map);
+   FOR_EACH_BB (bb)
+     {
+       find_replaceable_in_bb (table, bb);
+       gcc_assert (bitmap_empty_p (table->partition_in_use));
+ 
+ #ifdef ENABLE_CHECKING
+       {
+ 	unsigned i;
+ 	/* Make sure all the tables have been cleared out.  */
+ 	for (i = 0; i < num_ssa_names + 1; i++)
+ 	  {
+ 	    gcc_assert (table->partition_dependencies[i] == NULL);
+ 	    gcc_assert (table->expr_decl_uids[i] == NULL);
+ 	    if (i < num_var_partitions (map))
+ 	      gcc_assert (table->kill_list[i] == NULL);
+ 	  }
+       }
+ #endif
+     }
+ 
+   ret = free_temp_expr_table (table);
+   return ret;
+ }
+ 
+ 
+ /* Dump TER expression table EXPR to file F.  */
+ 
+ extern void
+ dump_replaceable_exprs (FILE *f, tree *expr)
+ {
+   tree stmt, var;
+   int x;
+ 
+   fprintf (f, "\nReplacing Expressions\n");
+   for (x = 0; x < (int)num_ssa_names; x++)
+     if (expr[x])
+       {
+         stmt = expr[x];
+ 	var = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF);
+ 	gcc_assert (var != NULL_TREE);
+ 	print_generic_expr (f, var, TDF_SLIM);
+ 	fprintf (f, " replace with --> ");
+ 	print_generic_expr (f, TREE_OPERAND (stmt, 1), TDF_SLIM);
+ 	fprintf (f, "\n");
+       }
+   fprintf (f, "\n");
+ }
+ 
+ 
+ #ifdef ENABLE_CHECKING
+ /* Dump the status of the various tables in the expression table.  This is used
+    exclusively to debug TER.  F is the place to send debug info and T is the
+    table being debugged.  */
+ 
+ extern void
+ debug_ter (FILE *f, temp_expr_table_p t)
+ {
+   unsigned x, y;
+   bitmap_iterator bi;
+ 
+   fprintf (f, "\nDumping current state of TER\n virtual partition = %d\n", 
+ 	   VIRTUAL_PARTITION (t));
+   if (t->replaceable_expressions)
+     dump_replaceable_exprs (f, t->replaceable_expressions);
+   fprintf (f, "Currently tracking the following expressions:\n");
+ 
+   for (x = 1; x < num_ssa_names; x++)
+     if (t->expr_decl_uids[x])
+       {
+         print_generic_expr (stderr, ssa_name (x), TDF_SLIM);
+         fprintf (f, " dep-parts : ");
+ 	if (t->partition_dependencies[x] 
+ 	    && !bitmap_empty_p (t->partition_dependencies[x]))
+ 	  {
+ 	    EXECUTE_IF_SET_IN_BITMAP (t->partition_dependencies[x], 0, y, bi)
+ 	      fprintf (f, "P%d ",y);
+ 	  }
+ 	fprintf (stderr, "   basedecls: ");
+ 	EXECUTE_IF_SET_IN_BITMAP (t->expr_decl_uids[x], 0, y, bi)
+ 	  fprintf (f, "%d ",y);
+ 	fprintf (stderr, "\n");
+       }
+ 
+   bitmap_print (f, t->partition_in_use, "Partitions in use ", 
+ 		"\npartition KILL lists:\n");
+ 
+   for (x = 0; x <= num_var_partitions (t->map); x++)
+     if (t->kill_list[x])
+       {
+         fprintf (f, "Partition %d : ", x);
+ 	EXECUTE_IF_SET_IN_BITMAP (t->kill_list[x], 0, y, bi)
+ 	  fprintf (f, "_%d ",y);
+       }
+ 
+   fprintf (f, "\n----------\n");
+ }
+ #endif

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