/* Language independent return value optimizations
- Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2007 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 2, or (at your option)
+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,
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, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
then we could either have the languages register the optimization or
we could change the gating function to check the current language. */
-static void
+static unsigned int
tree_nrv (void)
{
tree result = DECL_RESULT (current_function_decl);
/* If this function does not return an aggregate type in memory, then
there is nothing to do. */
if (!aggregate_value_p (result, current_function_decl))
- return;
+ return 0;
/* Look through each block for assignments to the RESULT_DECL. */
FOR_EACH_BB (bb)
if (ret_expr)
gcc_assert (ret_expr == result);
}
- else if (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_OPERAND (stmt, 0) == result)
+ else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ && GIMPLE_STMT_OPERAND (stmt, 0) == result)
{
- ret_expr = TREE_OPERAND (stmt, 1);
+ ret_expr = GIMPLE_STMT_OPERAND (stmt, 1);
/* Now verify that this return statement uses the same value
as any previously encountered return statement. */
than previous return statements, then we can not perform
NRV optimizations. */
if (found != ret_expr)
- return;
+ return 0;
}
else
found = ret_expr;
|| TREE_STATIC (found)
|| TREE_ADDRESSABLE (found)
|| DECL_ALIGN (found) > DECL_ALIGN (result)
- || !lang_hooks.types_compatible_p (TREE_TYPE (found),
- result_type))
- return;
+ || !useless_type_conversion_p (result_type,
+ TREE_TYPE (found)))
+ return 0;
+ }
+ else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+ {
+ tree addr = get_base_address (GIMPLE_STMT_OPERAND (stmt, 0));
+ /* If there's any MODIFY of component of RESULT,
+ then bail out. */
+ if (addr && addr == result)
+ return 0;
}
}
}
if (!found)
- return;
+ return 0;
/* If dumping details, then note once and only the NRV replacement. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
tree *tp = bsi_stmt_ptr (bsi);
/* If this is a copy from VAR to RESULT, remove it. */
- if (TREE_CODE (*tp) == MODIFY_EXPR
- && TREE_OPERAND (*tp, 0) == result
- && TREE_OPERAND (*tp, 1) == found)
- bsi_remove (&bsi);
+ if (TREE_CODE (*tp) == GIMPLE_MODIFY_STMT
+ && GIMPLE_STMT_OPERAND (*tp, 0) == result
+ && GIMPLE_STMT_OPERAND (*tp, 1) == found)
+ bsi_remove (&bsi, true);
else
{
walk_tree (tp, finalize_nrv_r, &data, 0);
/* FOUND is no longer used. Ensure it gets removed. */
var_ann (found)->used = 0;
+ return 0;
}
struct tree_opt_pass pass_nrv =
0 /* letter */
};
-/* Walk through the function looking for MODIFY_EXPRs with calls that
+/* Determine (pessimistically) whether DEST is available for NRV
+ optimization, where DEST is expected to be the LHS of a modify
+ expression where the RHS is a function returning an aggregate.
+
+ We search for a base VAR_DECL and look to see if it, or any of its
+ subvars are clobbered. Note that we could do better, for example, by
+ attempting to doing points-to analysis on INDIRECT_REFs. */
+
+static bool
+dest_safe_for_nrv_p (tree dest)
+{
+ subvar_t subvar;
+
+ while (handled_component_p (dest))
+ dest = TREE_OPERAND (dest, 0);
+
+ if (! SSA_VAR_P (dest))
+ return false;
+
+ if (TREE_CODE (dest) == SSA_NAME)
+ dest = SSA_NAME_VAR (dest);
+
+ if (is_call_clobbered (dest))
+ return false;
+ for (subvar = get_subvars_for_var (dest); subvar; subvar = subvar->next)
+ if (is_call_clobbered (subvar->var))
+ return false;
+ return true;
+}
+
+/* Walk through the function looking for GIMPLE_MODIFY_STMTs with calls that
return in memory on the RHS. For each of these, determine whether it is
safe to pass the address of the LHS as the return slot, and mark the
call appropriately if so.
escaped prior to the call. If it has, modifications to the local
variable will produce visible changes elsewhere, as in PR c++/19317. */
-static void
+static unsigned int
execute_return_slot_opt (void)
{
basic_block bb;
tree stmt = bsi_stmt (i);
tree call;
- if (TREE_CODE (stmt) == MODIFY_EXPR
- && (call = TREE_OPERAND (stmt, 1),
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ && (call = GIMPLE_STMT_OPERAND (stmt, 1),
TREE_CODE (call) == CALL_EXPR)
&& !CALL_EXPR_RETURN_SLOT_OPT (call)
&& aggregate_value_p (call, call))
- {
- def_operand_p def_p;
- ssa_op_iter op_iter;
-
- /* We determine whether or not the LHS address escapes by
- asking whether it is call clobbered. When the LHS isn't a
- simple decl, we need to check the VDEFs, so it's simplest
- to just loop through all the DEFs. */
- FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, op_iter, SSA_OP_ALL_DEFS)
- {
- tree def = DEF_FROM_PTR (def_p);
- if (TREE_CODE (def) == SSA_NAME)
- def = SSA_NAME_VAR (def);
- if (is_call_clobbered (def))
- goto unsafe;
- }
-
- /* No defs are call clobbered, so the optimization is safe. */
- CALL_EXPR_RETURN_SLOT_OPT (call) = 1;
- /* This is too late to mark the target addressable like we do
- in gimplify_modify_expr_rhs, but that's OK; anything that
- wasn't already addressable was handled there. */
-
- unsafe:;
- }
+ /* Check if the location being assigned to is
+ call-clobbered. */
+ CALL_EXPR_RETURN_SLOT_OPT (call) =
+ dest_safe_for_nrv_p (GIMPLE_STMT_OPERAND (stmt, 0)) ? 1 : 0;
}
}
+ return 0;
}
struct tree_opt_pass pass_return_slot =
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