/* Language independent return value optimizations
- Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2007, 2008, 2009 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, 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
That copy can often be avoided by directly constructing the return value
into the final destination mandated by the target's ABI.
- This is basically a generic equivalent to the C++ front-end's
+ This is basically a generic equivalent to the C++ front-end's
Named Return Value optimization. */
struct nrv_data
/* This is the function's RESULT_DECL. We will replace all occurrences
of VAR with RESULT_DECL when we apply this optimization. */
tree result;
+ int modified;
};
static tree finalize_nrv_r (tree *, int *, void *);
static tree
finalize_nrv_r (tree *tp, int *walk_subtrees, void *data)
{
- struct nrv_data *dp = (struct nrv_data *)data;
+ struct walk_stmt_info *wi = (struct walk_stmt_info *) data;
+ struct nrv_data *dp = (struct nrv_data *) wi->info;
/* No need to walk into types. */
if (TYPE_P (*tp))
/* Otherwise replace all occurrences of VAR with RESULT. */
else if (*tp == dp->var)
- *tp = dp->result;
+ {
+ *tp = dp->result;
+ dp->modified = 1;
+ }
/* Keep iterating. */
return NULL_TREE;
ever encounter languages which prevent this kind of optimization,
then we could either have the languages register the optimization or
we could change the gating function to check the current language. */
-
+
static unsigned int
tree_nrv (void)
{
tree result_type = TREE_TYPE (result);
tree found = NULL;
basic_block bb;
- block_stmt_iterator bsi;
+ gimple_stmt_iterator gsi;
struct nrv_data data;
/* If this function does not return an aggregate type in memory, then
if (!aggregate_value_p (result, current_function_decl))
return 0;
+ /* If a GIMPLE type is returned in memory, finalize_nrv_r might create
+ non-GIMPLE. */
+ if (is_gimple_reg_type (result_type))
+ return 0;
+
+ /* If the front end already did something like this, don't do it here. */
+ if (DECL_NAME (result))
+ return 0;
+
+ /* If the result has its address taken then it might be modified
+ by means not detected in the following loop. Bail out in this
+ case. */
+ if (TREE_ADDRESSABLE (result))
+ return 0;
+
/* Look through each block for assignments to the RESULT_DECL. */
FOR_EACH_BB (bb)
{
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
- tree stmt = bsi_stmt (bsi);
- tree ret_expr;
+ gimple stmt = gsi_stmt (gsi);
+ tree ret_val;
- if (TREE_CODE (stmt) == RETURN_EXPR)
+ if (gimple_code (stmt) == GIMPLE_RETURN)
{
/* In a function with an aggregate return value, the
gimplifier has changed all non-empty RETURN_EXPRs to
return the RESULT_DECL. */
- ret_expr = TREE_OPERAND (stmt, 0);
- if (ret_expr)
- gcc_assert (ret_expr == result);
+ ret_val = gimple_return_retval (stmt);
+ if (ret_val)
+ gcc_assert (ret_val == result);
}
- else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
- && GIMPLE_STMT_OPERAND (stmt, 0) == result)
+ else if (gimple_has_lhs (stmt)
+ && gimple_get_lhs (stmt) == result)
{
- ret_expr = GIMPLE_STMT_OPERAND (stmt, 1);
+ tree rhs;
+
+ if (!gimple_assign_copy_p (stmt))
+ return 0;
+
+ rhs = gimple_assign_rhs1 (stmt);
/* Now verify that this return statement uses the same value
as any previously encountered return statement. */
/* If we found a return statement using a different variable
than previous return statements, then we can not perform
NRV optimizations. */
- if (found != ret_expr)
+ if (found != rhs)
return 0;
}
else
- found = ret_expr;
+ found = rhs;
/* The returned value must be a local automatic variable of the
same type and alignment as the function's result. */
|| TREE_STATIC (found)
|| TREE_ADDRESSABLE (found)
|| DECL_ALIGN (found) > DECL_ALIGN (result)
- || !lang_hooks.types_compatible_p (TREE_TYPE (found),
- result_type))
+ || !useless_type_conversion_p (result_type,
+ TREE_TYPE (found)))
+ return 0;
+ }
+ else if (gimple_has_lhs (stmt))
+ {
+ tree addr = get_base_address (gimple_get_lhs (stmt));
+ /* If there's any MODIFY of component of RESULT,
+ then bail out. */
+ if (addr && addr == result)
return 0;
}
}
/* At this point we know that all the return statements return the
same local which has suitable attributes for NRV. Copy debugging
- information from FOUND to RESULT. */
- DECL_NAME (result) = DECL_NAME (found);
- DECL_SOURCE_LOCATION (result) = DECL_SOURCE_LOCATION (found);
- DECL_ABSTRACT_ORIGIN (result) = DECL_ABSTRACT_ORIGIN (found);
- TREE_ADDRESSABLE (result) = TREE_ADDRESSABLE (found);
+ information from FOUND to RESULT if it will be useful. But don't set
+ DECL_ABSTRACT_ORIGIN to point at another function. */
+ if (!DECL_IGNORED_P (found)
+ && !(DECL_ABSTRACT_ORIGIN (found)
+ && DECL_CONTEXT (DECL_ABSTRACT_ORIGIN (found)) != current_function_decl))
+ {
+ DECL_NAME (result) = DECL_NAME (found);
+ DECL_SOURCE_LOCATION (result) = DECL_SOURCE_LOCATION (found);
+ DECL_ABSTRACT_ORIGIN (result) = DECL_ABSTRACT_ORIGIN (found);
+ }
+
+ TREE_ADDRESSABLE (result) |= TREE_ADDRESSABLE (found);
/* Now walk through the function changing all references to VAR to be
RESULT. */
data.result = result;
FOR_EACH_BB (bb)
{
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
{
- tree *tp = bsi_stmt_ptr (bsi);
+ gimple stmt = gsi_stmt (gsi);
/* If this is a copy from VAR to RESULT, remove it. */
- if (TREE_CODE (*tp) == GIMPLE_MODIFY_STMT
- && GIMPLE_STMT_OPERAND (*tp, 0) == result
- && GIMPLE_STMT_OPERAND (*tp, 1) == found)
- bsi_remove (&bsi, true);
+ if (gimple_assign_copy_p (stmt)
+ && gimple_assign_lhs (stmt) == result
+ && gimple_assign_rhs1 (stmt) == found)
+ {
+ unlink_stmt_vdef (stmt);
+ gsi_remove (&gsi, true);
+ }
else
{
- walk_tree (tp, finalize_nrv_r, &data, 0);
- bsi_next (&bsi);
+ struct walk_stmt_info wi;
+ memset (&wi, 0, sizeof (wi));
+ wi.info = &data;
+ data.modified = 0;
+ walk_gimple_op (stmt, finalize_nrv_r, &wi);
+ if (data.modified)
+ update_stmt (stmt);
+ gsi_next (&gsi);
}
}
}
return 0;
}
-struct tree_opt_pass pass_nrv =
+static bool
+gate_pass_return_slot (void)
{
+ return optimize > 0;
+}
+
+struct gimple_opt_pass pass_nrv =
+{
+ {
+ GIMPLE_PASS,
"nrv", /* name */
- NULL, /* gate */
+ gate_pass_return_slot, /* gate */
tree_nrv, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_NRV, /* tv_id */
- PROP_cfg, /* properties_required */
+ PROP_ssa | PROP_cfg, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_ggc_collect, /* todo_flags_finish */
- 0 /* letter */
+ TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */
+ }
};
/* 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. */
+ DEST is available if it is not clobbered by the call. */
static bool
-dest_safe_for_nrv_p (tree dest)
+dest_safe_for_nrv_p (gimple call)
{
- switch (TREE_CODE (dest))
- {
- case VAR_DECL:
- {
- subvar_t subvar;
- 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;
- }
- case ARRAY_REF:
- case COMPONENT_REF:
- return dest_safe_for_nrv_p (TREE_OPERAND (dest, 0));
- default:
- return false;
- }
+ tree dest = gimple_call_lhs (call);
+
+ dest = get_base_address (dest);
+ if (! dest)
+ return false;
+
+ if (TREE_CODE (dest) == SSA_NAME)
+ return true;
+
+ if (call_may_clobber_ref_p (call, dest))
+ return false;
+
+ return true;
}
-/* Walk through the function looking for GIMPLE_MODIFY_STMTs with calls that
+/* Walk through the function looking for GIMPLE_ASSIGNs 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.
FOR_EACH_BB (bb)
{
- block_stmt_iterator i;
- for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
+ gimple_stmt_iterator gsi;
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
- tree stmt = bsi_stmt (i);
- tree call;
-
- 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))
- /* 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;
+ gimple stmt = gsi_stmt (gsi);
+ bool slot_opt_p;
+
+ if (is_gimple_call (stmt)
+ && gimple_call_lhs (stmt)
+ && !gimple_call_return_slot_opt_p (stmt)
+ && aggregate_value_p (TREE_TYPE (gimple_call_lhs (stmt)),
+ gimple_call_fndecl (stmt))
+ )
+ {
+ /* Check if the location being assigned to is
+ clobbered by the call. */
+ slot_opt_p = dest_safe_for_nrv_p (stmt);
+ gimple_call_set_return_slot_opt (stmt, slot_opt_p);
+ }
}
}
return 0;
}
-struct tree_opt_pass pass_return_slot =
+struct gimple_opt_pass pass_return_slot =
{
+ {
+ GIMPLE_PASS,
"retslot", /* name */
NULL, /* gate */
execute_return_slot_opt, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
- 0, /* tv_id */
- PROP_ssa | PROP_alias, /* properties_required */
+ TV_NONE, /* tv_id */
+ PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- 0, /* todo_flags_finish */
- 0 /* letter */
+ 0 /* todo_flags_finish */
+ }
};
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