tree
walk_gimple_stmt (gimple_stmt_iterator *gsi, walk_stmt_fn callback_stmt,
walk_tree_fn callback_op, struct walk_stmt_info *wi)
{
gimple *ret;
tree tree_ret;
gimple *stmt = gsi_stmt (*gsi);
if (wi)
{
wi->gsi = *gsi;
wi->removed_stmt = false;
if (wi->want_locations && gimple_has_location (stmt))
input_location = gimple_location (stmt);
}
ret = NULL;
/* Invoke the statement callback. Return if the callback handled
all of STMT operands by itself. */
if (callback_stmt)
{
bool handled_ops = false;
tree_ret = callback_stmt (gsi, &handled_ops, wi);
if (handled_ops)
return tree_ret;
/* If CALLBACK_STMT did not handle operands, it should not have
a value to return. */
gcc_assert (tree_ret == NULL);
if (wi && wi->removed_stmt)
return NULL;
/* Re-read stmt in case the callback changed it. */
stmt = gsi_stmt (*gsi);
}
/* If CALLBACK_OP is defined, invoke it on every operand of STMT. */
if (callback_op)
{
tree_ret = walk_gimple_op (stmt, callback_op, wi);
if (tree_ret)
return tree_ret;
}
/* If STMT can have statements inside (e.g. GIMPLE_BIND), walk them. */
switch (gimple_code (stmt))
{
case GIMPLE_BIND:
ret = walk_gimple_seq_mod (gimple_bind_body_ptr (as_a <gbind *> (stmt)),
callback_stmt, callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_CATCH:
ret = walk_gimple_seq_mod (gimple_catch_handler_ptr (
as_a <gcatch *> (stmt)),
callback_stmt, callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_EH_FILTER:
ret = walk_gimple_seq_mod (gimple_eh_filter_failure_ptr (stmt), callback_stmt,
callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_EH_ELSE:
{
geh_else *eh_else_stmt = as_a <geh_else *> (stmt);
ret = walk_gimple_seq_mod (gimple_eh_else_n_body_ptr (eh_else_stmt),
callback_stmt, callback_op, wi);
if (ret)
return wi->callback_result;
ret = walk_gimple_seq_mod (gimple_eh_else_e_body_ptr (eh_else_stmt),
callback_stmt, callback_op, wi);
if (ret)
return wi->callback_result;
}
break;
case GIMPLE_TRY:
ret = walk_gimple_seq_mod (gimple_try_eval_ptr (stmt), callback_stmt, callback_op,
wi);
if (ret)
return wi->callback_result;
ret = walk_gimple_seq_mod (gimple_try_cleanup_ptr (stmt), callback_stmt,
callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_OMP_FOR:
ret = walk_gimple_seq_mod (gimple_omp_for_pre_body_ptr (stmt), callback_stmt,
callback_op, wi);
if (ret)
return wi->callback_result;
/* FALL THROUGH. */
case GIMPLE_OMP_CRITICAL:
case GIMPLE_OMP_MASTER:
case GIMPLE_OMP_TASKGROUP:
case GIMPLE_OMP_ORDERED:
case GIMPLE_OMP_SECTION:
case GIMPLE_OMP_PARALLEL:
case GIMPLE_OMP_TASK:
case GIMPLE_OMP_SECTIONS:
case GIMPLE_OMP_SINGLE:
case GIMPLE_OMP_TARGET:
case GIMPLE_OMP_TEAMS:
ret = walk_gimple_seq_mod (gimple_omp_body_ptr (stmt), callback_stmt,
callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_WITH_CLEANUP_EXPR:
ret = walk_gimple_seq_mod (gimple_wce_cleanup_ptr (stmt), callback_stmt,
callback_op, wi);
if (ret)
return wi->callback_result;
break;
case GIMPLE_TRANSACTION:
ret = walk_gimple_seq_mod (gimple_transaction_body_ptr (
as_a <gtransaction *> (stmt)),
callback_stmt, callback_op, wi);
if (ret)
return wi->callback_result;
break;
default:
gcc_assert (!gimple_has_substatements (stmt));
break;
}
return NULL;
}
static unsigned int
tree_nrv (void)
{
tree result = DECL_RESULT (current_function_decl);
tree result_type = TREE_TYPE (result);
tree found = NULL;
basic_block bb;
gimple_stmt_iterator gsi;
struct nrv_data data;
/* 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 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;
/* Look through each block for assignments to the RESULT_DECL. */
FOR_EACH_BB (bb)
{
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple stmt = gsi_stmt (gsi);
tree ret_val;
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_val = gimple_return_retval (stmt);
if (ret_val)
gcc_assert (ret_val == result);
}
else if (is_gimple_assign (stmt)
&& gimple_assign_lhs (stmt) == result)
{
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 (found != NULL)
{
/* If we found a return statement using a different variable
than previous return statements, then we can not perform
NRV optimizations. */
if (found != rhs)
return 0;
}
else
found = rhs;
/* The returned value must be a local automatic variable of the
same type and alignment as the function's result. */
if (TREE_CODE (found) != VAR_DECL
|| TREE_THIS_VOLATILE (found)
|| DECL_CONTEXT (found) != current_function_decl
|| TREE_STATIC (found)
|| TREE_ADDRESSABLE (found)
|| DECL_ALIGN (found) > DECL_ALIGN (result)
|| !useless_type_conversion_p (result_type,
TREE_TYPE (found)))
return 0;
}
else if (is_gimple_assign (stmt))
{
tree addr = get_base_address (gimple_assign_lhs (stmt));
/* If there's any MODIFY of component of RESULT,
then bail out. */
if (addr && addr == result)
return 0;
}
}
}
if (!found)
return 0;
/* If dumping details, then note once and only the NRV replacement. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "NRV Replaced: ");
print_generic_expr (dump_file, found, dump_flags);
fprintf (dump_file, " with: ");
print_generic_expr (dump_file, result, dump_flags);
fprintf (dump_file, "\n");
}
/* 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);
/* Now walk through the function changing all references to VAR to be
RESULT. */
data.var = found;
data.result = result;
FOR_EACH_BB (bb)
{
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
{
gimple stmt = gsi_stmt (gsi);
/* If this is a copy from VAR to RESULT, remove it. */
if (gimple_assign_copy_p (stmt)
&& gimple_assign_lhs (stmt) == result
&& gimple_assign_rhs1 (stmt) == found)
gsi_remove (&gsi, true);
else
{
struct walk_stmt_info wi;
memset (&wi, 0, sizeof (wi));
wi.info = &data;
walk_gimple_op (stmt, finalize_nrv_r, &wi);
gsi_next (&gsi);
}
}
}
/* FOUND is no longer used. Ensure it gets removed. */
var_ann (found)->used = 0;
return 0;
}
