/* Tail call optimization on trees.
- Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009
+ Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
Free Software Foundation, Inc.
This file is part of GCC.
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
-#include "rtl.h"
#include "tm_p.h"
-#include "hard-reg-set.h"
#include "basic-block.h"
#include "function.h"
#include "tree-flow.h"
#include "tree-dump.h"
-#include "diagnostic.h"
+#include "gimple-pretty-print.h"
#include "except.h"
#include "tree-pass.h"
#include "flags.h"
#include "langhooks.h"
#include "dbgcnt.h"
+#include "target.h"
+#include "common/common-target.h"
/* The file implements the tail recursion elimination. It is also used to
analyze the tail calls in general, passing the results to the rtl level
return acc;
}
- To do this, we maintain two accumulators (a_acc and m_acc) that indicate
+ To do this, we maintain two accumulators (a_acc and m_acc) that indicate
when we reach the return x statement, we should return a_acc + x * m_acc
instead. They are initially initialized to 0 and 1, respectively,
so the semantics of the function is obviously preserved. If we are
1) Just return x, where x is not in any of the remaining special shapes.
We rewrite this to a gimple equivalent of return m_acc * x + a_acc.
-
+
2) return f (...), where f is the current function, is rewritten in a
classical tail-recursion elimination way, into assignment of arguments
and jump to the start of the function. Values of the accumulators
are unchanged.
-
+
3) return a + m * f(...), where a and m do not depend on call to f.
To preserve the semantics described before we want this to be rewritten
in such a way that we finally return
static bool
suitable_for_tail_opt_p (void)
{
- referenced_var_iterator rvi;
- tree var;
-
if (cfun->stdarg)
return false;
- /* No local variable nor structure field should be call-used. */
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (!is_global_var (var)
- && is_call_used (var))
- return false;
- }
-
return true;
}
/* Returns false when the function is not suitable for tail call optimization
/* If we are using sjlj exceptions, we may need to add a call to
_Unwind_SjLj_Unregister at exit of the function. Which means
that we cannot do any sibcall transformations. */
- if (USING_SJLJ_EXCEPTIONS && current_function_has_exception_handlers ())
+ if (targetm_common.except_unwind_info (&global_options) == UI_SJLJ
+ && current_function_has_exception_handlers ())
return false;
/* Any function that calls setjmp might have longjmp called from
but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */
for (param = DECL_ARGUMENTS (current_function_decl);
param;
- param = TREE_CHAIN (param))
+ param = DECL_CHAIN (param))
if (TREE_ADDRESSABLE (param))
return false;
bb->aux = &bb->aux;
while (1)
- {
+ {
at = SSA_NAME_DEF_STMT (expr);
bb = gimple_bb (at);
process_assignment (gimple stmt, gimple_stmt_iterator call, tree *m,
tree *a, tree *ass_var)
{
- tree op0, op1, non_ass_var;
+ tree op0, op1 = NULL_TREE, non_ass_var = NULL_TREE;
tree dest = gimple_assign_lhs (stmt);
enum tree_code code = gimple_assign_rhs_code (stmt);
enum gimple_rhs_class rhs_class = get_gimple_rhs_class (code);
tree src_var = gimple_assign_rhs1 (stmt);
-
+
/* See if this is a simple copy operation of an SSA name to the function
result. In that case we may have a simple tail call. Ignore type
conversions that can never produce extra code between the function
return true;
}
- if (rhs_class != GIMPLE_BINARY_RHS)
- return false;
+ switch (rhs_class)
+ {
+ case GIMPLE_BINARY_RHS:
+ op1 = gimple_assign_rhs2 (stmt);
+
+ /* Fall through. */
+
+ case GIMPLE_UNARY_RHS:
+ op0 = gimple_assign_rhs1 (stmt);
+ break;
+
+ default:
+ return false;
+ }
/* Accumulator optimizations will reverse the order of operations.
We can only do that for floating-point types if we're assuming
if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl))))
return false;
- /* We only handle the code like
-
- x = call ();
- y = m * x;
- z = y + a;
- return z;
-
- TODO -- Extend it for cases where the linear transformation of the output
- is expressed in a more complicated way. */
-
- op0 = gimple_assign_rhs1 (stmt);
- op1 = gimple_assign_rhs2 (stmt);
-
- if (op0 == *ass_var
+ if (rhs_class == GIMPLE_UNARY_RHS)
+ ;
+ else if (op0 == *ass_var
&& (non_ass_var = independent_of_stmt_p (op1, stmt, call)))
;
else if (op1 == *ass_var
switch (code)
{
case PLUS_EXPR:
- /* There should be no previous addition. TODO -- it should be fairly
- straightforward to lift this restriction -- just allow storing
- more complicated expressions in *A, and gimplify it in
- adjust_accumulator_values. */
- if (*a)
- return false;
*a = non_ass_var;
*ass_var = dest;
return true;
case MULT_EXPR:
- /* Similar remark applies here. Handling multiplication after addition
- is just slightly more complicated -- we need to multiply both *A and
- *M. */
- if (*a || *m)
- return false;
*m = non_ass_var;
*ass_var = dest;
return true;
- /* TODO -- Handle other codes (NEGATE_EXPR, MINUS_EXPR,
- POINTER_PLUS_EXPR). */
+ case NEGATE_EXPR:
+ if (FLOAT_TYPE_P (TREE_TYPE (op0)))
+ *m = build_real (TREE_TYPE (op0), dconstm1);
+ else if (INTEGRAL_TYPE_P (TREE_TYPE (op0)))
+ *m = build_int_cst (TREE_TYPE (op0), -1);
+ else
+ return false;
+
+ *ass_var = dest;
+ return true;
+
+ case MINUS_EXPR:
+ if (*ass_var == op0)
+ *a = fold_build1 (NEGATE_EXPR, TREE_TYPE (non_ass_var), non_ass_var);
+ else
+ {
+ if (FLOAT_TYPE_P (TREE_TYPE (non_ass_var)))
+ *m = build_real (TREE_TYPE (non_ass_var), dconstm1);
+ else if (INTEGRAL_TYPE_P (TREE_TYPE (non_ass_var)))
+ *m = build_int_cst (TREE_TYPE (non_ass_var), -1);
+ else
+ return false;
+
+ *a = fold_build1 (NEGATE_EXPR, TREE_TYPE (non_ass_var), non_ass_var);
+ }
+
+ *ass_var = dest;
+ return true;
+
+ /* TODO -- Handle POINTER_PLUS_EXPR. */
default:
return false;
{
basic_block dest = e->dest;
gimple_stmt_iterator gsi;
-
+
for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple phi = gsi_stmt (gsi);
tree m, a;
basic_block abb;
size_t idx;
+ tree var;
+ referenced_var_iterator rvi;
if (!single_succ_p (bb))
return;
{
stmt = gsi_stmt (gsi);
- /* Ignore labels. */
- if (gimple_code (stmt) == GIMPLE_LABEL)
+ /* Ignore labels, returns, clobbers and debug stmts. */
+ if (gimple_code (stmt) == GIMPLE_LABEL
+ || gimple_code (stmt) == GIMPLE_RETURN
+ || gimple_clobber_p (stmt)
+ || is_gimple_debug (stmt))
continue;
/* Check for a call. */
return;
}
- /* If the LHS of our call is not just a simple register, we can't
+ /* If the LHS of our call is not just a simple register, we can't
transform this into a tail or sibling call. This situation happens,
in (e.g.) "*p = foo()" where foo returns a struct. In this case
we won't have a temporary here, but we need to carry out the side
if (func == current_function_decl)
{
tree arg;
+
for (param = DECL_ARGUMENTS (func), idx = 0;
param && idx < gimple_call_num_args (call);
- param = TREE_CHAIN (param), idx ++)
+ param = DECL_CHAIN (param), idx ++)
{
arg = gimple_call_arg (call, idx);
if (param != arg)
tail_recursion = true;
}
+ /* Make sure the tail invocation of this function does not refer
+ to local variables. */
+ FOR_EACH_REFERENCED_VAR (cfun, var, rvi)
+ {
+ if (TREE_CODE (var) != PARM_DECL
+ && auto_var_in_fn_p (var, cfun->decl)
+ && (ref_maybe_used_by_stmt_p (call, var)
+ || call_may_clobber_ref_p (call, var)))
+ return;
+ }
+
/* Now check the statements after the call. None of them has virtual
operands, so they may only depend on the call through its return
value. The return value should also be dependent on each of them,
agsi = gsi;
while (1)
{
+ tree tmp_a = NULL_TREE;
+ tree tmp_m = NULL_TREE;
gsi_next (&agsi);
while (gsi_end_p (agsi))
if (gimple_code (stmt) == GIMPLE_RETURN)
break;
+ if (gimple_clobber_p (stmt))
+ continue;
+
+ if (is_gimple_debug (stmt))
+ continue;
+
if (gimple_code (stmt) != GIMPLE_ASSIGN)
return;
/* This is a gimple assign. */
- if (! process_assignment (stmt, gsi, &m, &a, &ass_var))
+ if (! process_assignment (stmt, gsi, &tmp_m, &tmp_a, &ass_var))
return;
+
+ if (tmp_a)
+ {
+ tree type = TREE_TYPE (tmp_a);
+ if (a)
+ a = fold_build2 (PLUS_EXPR, type, fold_convert (type, a), tmp_a);
+ else
+ a = tmp_a;
+ }
+ if (tmp_m)
+ {
+ tree type = TREE_TYPE (tmp_m);
+ if (m)
+ m = fold_build2 (MULT_EXPR, type, fold_convert (type, m), tmp_m);
+ else
+ m = tmp_m;
+
+ if (a)
+ a = fold_build2 (MULT_EXPR, type, fold_convert (type, a), tmp_m);
+ }
}
/* See if this is a tail call we can handle. */
if (!tail_recursion && (m || a))
return;
+ /* For pointers don't allow additions or multiplications. */
+ if ((m || a)
+ && POINTER_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl))))
+ return;
+
nw = XNEW (struct tailcall);
nw->call_gsi = gsi;
break;
gcc_assert (!gsi_end_p (gsi));
- add_phi_arg (gsi_stmt (gsi), phi_arg, e);
+ add_phi_arg (gsi_stmt (gsi), phi_arg, e, UNKNOWN_LOCATION);
}
/* Creates a GIMPLE statement which computes the operation specified by
- CODE, OP0 and OP1 to a new variable with name LABEL and inserts the
- statement in the position specified by GSI and UPDATE. Returns the
+ CODE, ACC and OP1 to a new variable with name LABEL and inserts the
+ statement in the position specified by GSI. Returns the
tree node of the statement's result. */
static tree
-adjust_return_value_with_ops (enum tree_code code, const char *label,
- tree op0, tree op1, gimple_stmt_iterator gsi,
- enum gsi_iterator_update update)
+adjust_return_value_with_ops (enum tree_code code, const char *label,
+ tree acc, tree op1, gimple_stmt_iterator gsi)
{
tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
- tree tmp = create_tmp_var (ret_type, label);
- gimple stmt = gimple_build_assign_with_ops (code, tmp, op0, op1);
+ tree tmp = create_tmp_reg (ret_type, label);
+ gimple stmt;
tree result;
add_referenced_var (tmp);
+
+ if (types_compatible_p (TREE_TYPE (acc), TREE_TYPE (op1)))
+ stmt = gimple_build_assign_with_ops (code, tmp, acc, op1);
+ else
+ {
+ tree rhs = fold_convert (TREE_TYPE (acc),
+ fold_build2 (code,
+ TREE_TYPE (op1),
+ fold_convert (TREE_TYPE (op1), acc),
+ op1));
+ rhs = force_gimple_operand_gsi (&gsi, rhs,
+ false, NULL, true, GSI_SAME_STMT);
+ stmt = gimple_build_assign (NULL_TREE, rhs);
+ }
+
result = make_ssa_name (tmp, stmt);
gimple_assign_set_lhs (stmt, result);
update_stmt (stmt);
- gsi_insert_before (&gsi, stmt, update);
+ gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
return result;
}
-/* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
+/* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
the computation specified by CODE and OP1 and insert the statement
at the position specified by GSI as a new statement. Returns new SSA name
of updated accumulator. */
update_accumulator_with_ops (enum tree_code code, tree acc, tree op1,
gimple_stmt_iterator gsi)
{
- gimple stmt = gimple_build_assign_with_ops (code, SSA_NAME_VAR (acc), acc,
- op1);
- tree var = make_ssa_name (SSA_NAME_VAR (acc), stmt);
+ gimple stmt;
+ tree var;
+ if (types_compatible_p (TREE_TYPE (acc), TREE_TYPE (op1)))
+ stmt = gimple_build_assign_with_ops (code, SSA_NAME_VAR (acc), acc, op1);
+ else
+ {
+ tree rhs = fold_convert (TREE_TYPE (acc),
+ fold_build2 (code,
+ TREE_TYPE (op1),
+ fold_convert (TREE_TYPE (op1), acc),
+ op1));
+ rhs = force_gimple_operand_gsi (&gsi, rhs,
+ false, NULL, false, GSI_CONTINUE_LINKING);
+ stmt = gimple_build_assign (NULL_TREE, rhs);
+ }
+ var = make_ssa_name (SSA_NAME_VAR (acc), stmt);
gimple_assign_set_lhs (stmt, var);
update_stmt (stmt);
gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
static void
adjust_accumulator_values (gimple_stmt_iterator gsi, tree m, tree a, edge back)
{
- tree var, a_acc_arg = a_acc, m_acc_arg = m_acc;
+ tree var, a_acc_arg, m_acc_arg;
+ if (m)
+ m = force_gimple_operand_gsi (&gsi, m, true, NULL, true, GSI_SAME_STMT);
+ if (a)
+ a = force_gimple_operand_gsi (&gsi, a, true, NULL, true, GSI_SAME_STMT);
+
+ a_acc_arg = a_acc;
+ m_acc_arg = m_acc;
if (a)
{
if (m_acc)
var = m_acc;
else
var = adjust_return_value_with_ops (MULT_EXPR, "acc_tmp", m_acc,
- a, gsi, GSI_NEW_STMT);
+ a, gsi);
}
else
var = a;
if (m)
retval = adjust_return_value_with_ops (MULT_EXPR, "mul_tmp", m_acc, retval,
- gsi, GSI_SAME_STMT);
+ gsi);
if (a)
retval = adjust_return_value_with_ops (PLUS_EXPR, "acc_tmp", a_acc, retval,
- gsi, GSI_SAME_STMT);
+ gsi);
gimple_return_set_retval (ret_stmt, retval);
update_stmt (ret_stmt);
}
if (!is_gimple_reg (param) || !var_ann (param))
return false;
-
+
/* Parameters that are only defined but never used need not be copied. */
def = gimple_default_def (cfun, param);
if (!def)
for (param = DECL_ARGUMENTS (current_function_decl),
idx = 0, gsi = gsi_start_phis (first);
param;
- param = TREE_CHAIN (param), idx++)
+ param = DECL_CHAIN (param), idx++)
{
if (!arg_needs_copy_p (param))
continue;
phi = gsi_stmt (gsi);
gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi)));
- add_phi_arg (phi, arg, e);
+ add_phi_arg (phi, arg, e, gimple_location (stmt));
gsi_next (&gsi);
}
this, we cannot do much better than to rebuild the ssa form for
possibly affected virtual ssa names from scratch. */
- FOR_EACH_REFERENCED_VAR (var, rvi)
+ FOR_EACH_REFERENCED_VAR (cfun, var, rvi)
{
if (!is_gimple_reg (var) && gimple_default_def (cfun, var) != NULL_TREE)
mark_sym_for_renaming (var);
create_tailcall_accumulator (const char *label, basic_block bb, tree init)
{
tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
- tree tmp = create_tmp_var (ret_type, label);
+ tree tmp = create_tmp_reg (ret_type, label);
gimple phi;
add_referenced_var (tmp);
phi = create_phi_node (tmp, bb);
/* RET_TYPE can be a float when -ffast-maths is enabled. */
- add_phi_arg (phi, fold_convert (ret_type, init), single_pred_edge (bb));
+ add_phi_arg (phi, fold_convert (ret_type, init), single_pred_edge (bb),
+ UNKNOWN_LOCATION);
return PHI_RESULT (phi);
}
-
+
/* Optimizes tail calls in the function, turning the tail recursion
into iteration. */
/* Copy the args if needed. */
for (param = DECL_ARGUMENTS (current_function_decl);
param;
- param = TREE_CHAIN (param))
+ param = DECL_CHAIN (param))
if (arg_needs_copy_p (param))
{
tree name = gimple_default_def (cfun, param);
set_default_def (param, new_name);
phi = create_phi_node (name, first);
SSA_NAME_DEF_STMT (name) = phi;
- add_phi_arg (phi, new_name, single_pred_edge (first));
+ add_phi_arg (phi, new_name, single_pred_edge (first),
+ EXPR_LOCATION (param));
}
phis_constructed = true;
}
integer_one_node);
}
+ if (a_acc || m_acc)
+ {
+ /* When the tail call elimination using accumulators is performed,
+ statements adding the accumulated value are inserted at all exits.
+ This turns all other tail calls to non-tail ones. */
+ opt_tailcalls = false;
+ }
+
for (; tailcalls; tailcalls = next)
{
next = tailcalls->next;
return tree_optimize_tail_calls_1 (true);
}
-struct gimple_opt_pass pass_tail_recursion =
+struct gimple_opt_pass pass_tail_recursion =
{
{
GIMPLE_PASS,
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ TODO_verify_ssa /* todo_flags_finish */
}
};
-struct gimple_opt_pass pass_tail_calls =
+struct gimple_opt_pass pass_tail_calls =
{
{
GIMPLE_PASS,
NULL, /* next */
0, /* static_pass_number */
TV_NONE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ TODO_verify_ssa /* todo_flags_finish */
}
};
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