/* Tail call optimization on trees.
- Copyright (C) 2003 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2004, 2005, 2006, 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, 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"
#include "tree-pass.h"
#include "flags.h"
#include "langhooks.h"
+#include "dbgcnt.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
struct tailcall
{
- /* The block in that the call occur. */
- basic_block call_block;
-
/* The iterator pointing to the call statement. */
- block_stmt_iterator call_bsi;
+ gimple_stmt_iterator call_gsi;
/* True if it is a call to the current function. */
bool tail_recursion;
static bool
suitable_for_tail_opt_p (void)
{
- int i;
+ referenced_var_iterator rvi;
+ tree var;
- if (current_function_stdarg)
+ if (cfun->stdarg)
return false;
- /* No local variable should be call-clobbered. We ignore any kind
- of memory tag, as these are not real variables. */
- for (i = 0; i < (int) VARRAY_ACTIVE_SIZE (referenced_vars); i++)
+ /* No local variable nor structure field should be call-used. */
+ FOR_EACH_REFERENCED_VAR (var, rvi)
{
- tree var = VARRAY_TREE (referenced_vars, i);
-
- if (!(TREE_STATIC (var) || DECL_EXTERNAL (var))
- && var_ann (var)->mem_tag_kind == NOT_A_TAG
- && is_call_clobbered (var))
+ if (!is_global_var (var)
+ && is_call_used (var))
return false;
}
static bool
suitable_for_tail_call_opt_p (void)
{
+ tree param;
+
/* alloca (until we have stack slot life analysis) inhibits
sibling call optimizations, but not tail recursion. */
- if (current_function_calls_alloca)
+ if (cfun->calls_alloca)
return false;
/* If we are using sjlj exceptions, we may need to add a call to
/* Any function that calls setjmp might have longjmp called from
any called function. ??? We really should represent this
properly in the CFG so that this needn't be special cased. */
- if (current_function_calls_setjmp)
+ if (cfun->calls_setjmp)
return false;
+ /* ??? It is OK if the argument of a function is taken in some cases,
+ 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))
+ if (TREE_ADDRESSABLE (param))
+ return false;
+
return true;
}
/* Checks whether the expression EXPR in stmt AT is independent of the
- statement pointed by BSI (in a sense that we already know EXPR's value
- at BSI). We use the fact that we are only called from the chain of
+ statement pointed to by GSI (in a sense that we already know EXPR's value
+ at GSI). We use the fact that we are only called from the chain of
basic blocks that have only single successor. Returns the expression
- containing the value of EXPR at BSI. */
+ containing the value of EXPR at GSI. */
static tree
-independent_of_stmt_p (tree expr, tree at, block_stmt_iterator bsi)
+independent_of_stmt_p (tree expr, gimple at, gimple_stmt_iterator gsi)
{
basic_block bb, call_bb, at_bb;
edge e;
+ edge_iterator ei;
if (is_gimple_min_invariant (expr))
return expr;
return NULL_TREE;
/* Mark the blocks in the chain leading to the end. */
- at_bb = bb_for_stmt (at);
- call_bb = bb_for_stmt (bsi_stmt (bsi));
- for (bb = call_bb; bb != at_bb; bb = bb->succ->dest)
+ at_bb = gimple_bb (at);
+ call_bb = gimple_bb (gsi_stmt (gsi));
+ for (bb = call_bb; bb != at_bb; bb = single_succ (bb))
bb->aux = &bb->aux;
bb->aux = &bb->aux;
while (1)
- {
+ {
at = SSA_NAME_DEF_STMT (expr);
- bb = bb_for_stmt (at);
+ bb = gimple_bb (at);
/* The default definition or defined before the chain. */
if (!bb || !bb->aux)
if (bb == call_bb)
{
- for (; !bsi_end_p (bsi); bsi_next (&bsi))
- if (bsi_stmt (bsi) == at)
+ for (; !gsi_end_p (gsi); gsi_next (&gsi))
+ if (gsi_stmt (gsi) == at)
break;
- if (!bsi_end_p (bsi))
+ if (!gsi_end_p (gsi))
expr = NULL_TREE;
break;
}
- if (TREE_CODE (at) != PHI_NODE)
+ if (gimple_code (at) != GIMPLE_PHI)
{
expr = NULL_TREE;
break;
}
- for (e = bb->pred; e; e = e->pred_next)
+ FOR_EACH_EDGE (e, ei, bb->preds)
if (e->src->aux)
break;
- if (!e)
- abort ();
+ gcc_assert (e);
expr = PHI_ARG_DEF_FROM_EDGE (at, e);
if (TREE_CODE (expr) != SSA_NAME)
}
/* Unmark the blocks. */
- for (bb = call_bb; bb != at_bb; bb = bb->succ->dest)
+ for (bb = call_bb; bb != at_bb; bb = single_succ (bb))
bb->aux = NULL;
bb->aux = NULL;
return expr;
}
-/* Simulates the effect of an assignment of ASS in STMT on the return value
- of the tail recursive CALL passed in ASS_VAR. M and A are the
- multiplicative and the additive factor for the real return value. */
+/* Simulates the effect of an assignment STMT on the return value of the tail
+ recursive CALL passed in ASS_VAR. M and A are the multiplicative and the
+ additive factor for the real return value. */
static bool
-process_assignment (tree ass, tree stmt, block_stmt_iterator call, tree *m,
+process_assignment (gimple stmt, gimple_stmt_iterator call, tree *m,
tree *a, tree *ass_var)
{
tree op0, op1, non_ass_var;
- tree dest = TREE_OPERAND (ass, 0);
- tree src = TREE_OPERAND (ass, 1);
- enum tree_code code = TREE_CODE (src);
- tree src_var = src;
+ 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
call and the function return. */
- STRIP_NOPS (src_var);
- if (TREE_CODE (src_var) == SSA_NAME)
+ if ((rhs_class == GIMPLE_SINGLE_RHS || gimple_assign_cast_p (stmt))
+ && (TREE_CODE (src_var) == SSA_NAME))
{
+ /* Reject a tailcall if the type conversion might need
+ additional code. */
+ if (gimple_assign_cast_p (stmt)
+ && TYPE_MODE (TREE_TYPE (dest)) != TYPE_MODE (TREE_TYPE (src_var)))
+ return false;
+
if (src_var != *ass_var)
return false;
return true;
}
- if (TREE_CODE_CLASS (code) != '2')
+ if (rhs_class != GIMPLE_BINARY_RHS)
return false;
+ /* Accumulator optimizations will reverse the order of operations.
+ We can only do that for floating-point types if we're assuming
+ that addition and multiplication are associative. */
+ if (!flag_associative_math)
+ if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl))))
+ return false;
+
/* We only handle the code like
x = call ();
TODO -- Extend it for cases where the linear transformation of the output
is expressed in a more complicated way. */
- op0 = TREE_OPERAND (src, 0);
- op1 = TREE_OPERAND (src, 1);
+ op0 = gimple_assign_rhs1 (stmt);
+ op1 = gimple_assign_rhs2 (stmt);
if (op0 == *ass_var
&& (non_ass_var = independent_of_stmt_p (op1, stmt, call)))
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). */
+ /* TODO -- Handle other codes (NEGATE_EXPR, MINUS_EXPR,
+ POINTER_PLUS_EXPR). */
default:
return false;
propagate_through_phis (tree var, edge e)
{
basic_block dest = e->dest;
- tree phi;
-
- for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
- if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var)
- return PHI_RESULT (phi);
+ gimple_stmt_iterator gsi;
+ for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple phi = gsi_stmt (gsi);
+ if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var)
+ return PHI_RESULT (phi);
+ }
return var;
}
static void
find_tail_calls (basic_block bb, struct tailcall **ret)
{
- tree ass_var, ret_var, stmt, func, param, args, call = NULL_TREE;
- block_stmt_iterator bsi, absi;
+ tree ass_var = NULL_TREE, ret_var, func, param;
+ gimple stmt, call = NULL;
+ gimple_stmt_iterator gsi, agsi;
bool tail_recursion;
struct tailcall *nw;
edge e;
tree m, a;
basic_block abb;
- stmt_ann_t ann;
+ size_t idx;
- if (bb->succ->succ_next)
+ if (!single_succ_p (bb))
return;
- for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi))
+ for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
{
- stmt = bsi_stmt (bsi);
+ stmt = gsi_stmt (gsi);
/* Ignore labels. */
- if (TREE_CODE (stmt) == LABEL_EXPR)
+ if (gimple_code (stmt) == GIMPLE_LABEL || is_gimple_debug (stmt))
continue;
- get_stmt_operands (stmt);
-
/* Check for a call. */
- if (TREE_CODE (stmt) == MODIFY_EXPR)
+ if (is_gimple_call (stmt))
{
- ass_var = TREE_OPERAND (stmt, 0);
- call = TREE_OPERAND (stmt, 1);
- if (TREE_CODE (call) == WITH_SIZE_EXPR)
- call = TREE_OPERAND (call, 0);
- }
- else
- {
- ass_var = NULL_TREE;
call = stmt;
+ ass_var = gimple_call_lhs (stmt);
+ break;
}
- if (TREE_CODE (call) == CALL_EXPR)
- break;
-
- /* If the statement has virtual or volatile operands, fail. */
- ann = stmt_ann (stmt);
- if (NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann))
- || NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann))
- || NUM_VUSES (VUSE_OPS (ann))
- || ann->has_volatile_ops)
+ /* If the statement references memory or volatile operands, fail. */
+ if (gimple_references_memory_p (stmt)
+ || gimple_has_volatile_ops (stmt))
return;
}
- if (bsi_end_p (bsi))
+ if (gsi_end_p (gsi))
{
+ edge_iterator ei;
/* Recurse to the predecessors. */
- for (e = bb->pred; e; e = e->pred_next)
+ FOR_EACH_EDGE (e, ei, bb->preds)
find_tail_calls (e->src, ret);
return;
}
+ /* 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
+ effect anyway, so tailcall is impossible.
+
+ ??? In some situations (when the struct is returned in memory via
+ invisible argument) we could deal with this, e.g. by passing 'p'
+ itself as that argument to foo, but it's too early to do this here,
+ and expand_call() will not handle it anyway. If it ever can, then
+ we need to revisit this here, to allow that situation. */
+ if (ass_var && !is_gimple_reg (ass_var))
+ return;
+
/* We found the call, check whether it is suitable. */
tail_recursion = false;
- func = get_callee_fndecl (call);
+ func = gimple_call_fndecl (call);
if (func == current_function_decl)
{
- for (param = DECL_ARGUMENTS (func), args = TREE_OPERAND (call, 1);
- param && args;
- param = TREE_CHAIN (param), args = TREE_CHAIN (args))
+ tree arg;
+ for (param = DECL_ARGUMENTS (func), idx = 0;
+ param && idx < gimple_call_num_args (call);
+ param = TREE_CHAIN (param), idx ++)
{
- tree arg = TREE_VALUE (args);
- if (param != arg
- /* Make sure there are no problems with copying. Note we must
+ arg = gimple_call_arg (call, idx);
+ if (param != arg)
+ {
+ /* Make sure there are no problems with copying. The parameter
have a copyable type and the two arguments must have reasonably
equivalent types. The latter requirement could be relaxed if
we emitted a suitable type conversion statement. */
- && (!is_gimple_reg_type (TREE_TYPE (param))
- || !lang_hooks.types_compatible_p (TREE_TYPE (param),
- TREE_TYPE (arg))))
- break;
+ if (!is_gimple_reg_type (TREE_TYPE (param))
+ || !useless_type_conversion_p (TREE_TYPE (param),
+ TREE_TYPE (arg)))
+ break;
+
+ /* The parameter should be a real operand, so that phi node
+ created for it at the start of the function has the meaning
+ of copying the value. This test implies is_gimple_reg_type
+ from the previous condition, however this one could be
+ relaxed by being more careful with copying the new value
+ of the parameter (emitting appropriate GIMPLE_ASSIGN and
+ updating the virtual operands). */
+ if (!is_gimple_reg (param))
+ break;
+ }
}
- if (!args && !param)
+ if (idx == gimple_call_num_args (call) && !param)
tail_recursion = true;
}
a = NULL_TREE;
abb = bb;
- absi = bsi;
+ agsi = gsi;
while (1)
{
- bsi_next (&absi);
+ tree tmp_a = NULL_TREE;
+ tree tmp_m = NULL_TREE;
+ gsi_next (&agsi);
- while (bsi_end_p (absi))
+ while (gsi_end_p (agsi))
{
- ass_var = propagate_through_phis (ass_var, abb->succ);
- abb = abb->succ->dest;
- absi = bsi_start (abb);
+ ass_var = propagate_through_phis (ass_var, single_succ_edge (abb));
+ abb = single_succ (abb);
+ agsi = gsi_start_bb (abb);
}
- stmt = bsi_stmt (absi);
+ stmt = gsi_stmt (agsi);
- if (TREE_CODE (stmt) == LABEL_EXPR)
+ if (gimple_code (stmt) == GIMPLE_LABEL)
continue;
- if (TREE_CODE (stmt) == RETURN_EXPR)
+ if (gimple_code (stmt) == GIMPLE_RETURN)
break;
- if (TREE_CODE (stmt) != MODIFY_EXPR)
- return;
+ if (is_gimple_debug (stmt))
+ continue;
- if (!process_assignment (stmt, stmt, bsi, &m, &a, &ass_var))
+ if (gimple_code (stmt) != GIMPLE_ASSIGN)
return;
- }
- /* See if this is a tail call we can handle. */
- ret_var = TREE_OPERAND (stmt, 0);
- if (ret_var
- && TREE_CODE (ret_var) == MODIFY_EXPR)
- {
- tree ret_op = TREE_OPERAND (ret_var, 1);
- STRIP_NOPS (ret_op);
- if (!tail_recursion
- && TREE_CODE (ret_op) != SSA_NAME)
+ /* This is a gimple assign. */
+ if (! process_assignment (stmt, gsi, &tmp_m, &tmp_a, &ass_var))
return;
- if (!process_assignment (ret_var, stmt, bsi, &m, &a, &ass_var))
- return;
- ret_var = TREE_OPERAND (ret_var, 0);
+ if (tmp_a)
+ {
+ if (a)
+ a = fold_build2 (PLUS_EXPR, TREE_TYPE (tmp_a), a, tmp_a);
+ else
+ a = tmp_a;
+ }
+ if (tmp_m)
+ {
+ if (m)
+ m = fold_build2 (MULT_EXPR, TREE_TYPE (tmp_m), m, tmp_m);
+ else
+ m = tmp_m;
+
+ if (a)
+ a = fold_build2 (MULT_EXPR, TREE_TYPE (tmp_m), a, tmp_m);
+ }
}
+ /* See if this is a tail call we can handle. */
+ ret_var = gimple_return_retval (stmt);
+
/* We may proceed if there either is no return value, or the return value
is identical to the call's return. */
if (ret_var
if (!tail_recursion && (m || a))
return;
- nw = xmalloc (sizeof (struct tailcall));
+ nw = XNEW (struct tailcall);
- nw->call_block = bb;
- nw->call_bsi = bsi;
+ nw->call_gsi = gsi;
nw->tail_recursion = tail_recursion;
*ret = nw;
}
-/* Adjust the accumulator values according to A and M after BSI, and update
- the phi nodes on edge BACK. */
+/* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */
static void
-adjust_accumulator_values (block_stmt_iterator bsi, tree m, tree a, edge back)
+add_successor_phi_arg (edge e, tree var, tree phi_arg)
+{
+ gimple_stmt_iterator gsi;
+
+ for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
+ if (PHI_RESULT (gsi_stmt (gsi)) == var)
+ break;
+
+ gcc_assert (!gsi_end_p (gsi));
+ 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
+ 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)
{
- tree stmt, var, phi, tmp;
+
tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
- tree a_acc_arg = a_acc, m_acc_arg = m_acc;
+ tree tmp = create_tmp_var (ret_type, label);
+ gimple stmt = gimple_build_assign_with_ops (code, tmp, op0, op1);
+ tree result;
+
+ if (TREE_CODE (ret_type) == COMPLEX_TYPE
+ || TREE_CODE (ret_type) == VECTOR_TYPE)
+ DECL_GIMPLE_REG_P (tmp) = 1;
+ add_referenced_var (tmp);
+ result = make_ssa_name (tmp, stmt);
+ gimple_assign_set_lhs (stmt, result);
+ update_stmt (stmt);
+ gsi_insert_before (&gsi, stmt, update);
+ return result;
+}
+
+/* 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. */
+static tree
+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_assign_set_lhs (stmt, var);
+ update_stmt (stmt);
+ gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
+ return var;
+}
+
+/* Adjust the accumulator values according to A and M after GSI, and update
+ the phi nodes on edge BACK. */
+
+static void
+adjust_accumulator_values (gimple_stmt_iterator gsi, tree m, tree a, edge back)
+{
+ 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)
if (integer_onep (a))
var = m_acc;
else
- {
- stmt = build (MODIFY_EXPR, ret_type, NULL_TREE,
- build (MULT_EXPR, ret_type, m_acc, a));
-
- tmp = create_tmp_var (ret_type, "acc_tmp");
- add_referenced_tmp_var (tmp);
-
- var = make_ssa_name (tmp, stmt);
- TREE_OPERAND (stmt, 0) = var;
- bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
- }
+ var = adjust_return_value_with_ops (MULT_EXPR, "acc_tmp", m_acc,
+ a, gsi, GSI_NEW_STMT);
}
else
var = a;
- stmt = build (MODIFY_EXPR, ret_type, NULL_TREE,
- build (PLUS_EXPR, ret_type, a_acc, var));
- var = make_ssa_name (SSA_NAME_VAR (a_acc), stmt);
- TREE_OPERAND (stmt, 0) = var;
- bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
- a_acc_arg = var;
+ a_acc_arg = update_accumulator_with_ops (PLUS_EXPR, a_acc, var, gsi);
}
if (m)
- {
- stmt = build (MODIFY_EXPR, ret_type, NULL_TREE,
- build (MULT_EXPR, ret_type, m_acc, m));
- var = make_ssa_name (SSA_NAME_VAR (m_acc), stmt);
- TREE_OPERAND (stmt, 0) = var;
- bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
- m_acc_arg = var;
- }
+ m_acc_arg = update_accumulator_with_ops (MULT_EXPR, m_acc, m, gsi);
if (a_acc)
- {
- for (phi = phi_nodes (back->dest); phi; phi = PHI_CHAIN (phi))
- if (PHI_RESULT (phi) == a_acc)
- break;
-
- add_phi_arg (&phi, a_acc_arg, back);
- }
+ add_successor_phi_arg (back, a_acc, a_acc_arg);
if (m_acc)
- {
- for (phi = phi_nodes (back->dest); phi; phi = PHI_CHAIN (phi))
- if (PHI_RESULT (phi) == m_acc)
- break;
-
- add_phi_arg (&phi, m_acc_arg, back);
- }
+ add_successor_phi_arg (back, m_acc, m_acc_arg);
}
/* Adjust value of the return at the end of BB according to M and A
static void
adjust_return_value (basic_block bb, tree m, tree a)
{
- tree ret_stmt = last_stmt (bb), ret_var, var, stmt, tmp;
- tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
- block_stmt_iterator bsi = bsi_last (bb);
+ tree retval;
+ gimple ret_stmt = gimple_seq_last_stmt (bb_seq (bb));
+ gimple_stmt_iterator gsi = gsi_last_bb (bb);
- if (TREE_CODE (ret_stmt) != RETURN_EXPR)
- abort ();
+ gcc_assert (gimple_code (ret_stmt) == GIMPLE_RETURN);
- ret_var = TREE_OPERAND (ret_stmt, 0);
- if (!ret_var)
+ retval = gimple_return_retval (ret_stmt);
+ if (!retval || retval == error_mark_node)
return;
- if (TREE_CODE (ret_var) == MODIFY_EXPR)
- {
- ret_var->common.ann = (tree_ann_t) stmt_ann (ret_stmt);
- bsi_replace (&bsi, ret_var, true);
- SSA_NAME_DEF_STMT (TREE_OPERAND (ret_var, 0)) = ret_var;
- ret_var = TREE_OPERAND (ret_var, 0);
- ret_stmt = build1 (RETURN_EXPR, TREE_TYPE (ret_stmt), ret_var);
- bsi_insert_after (&bsi, ret_stmt, BSI_NEW_STMT);
- }
-
if (m)
- {
- stmt = build (MODIFY_EXPR, ret_type, NULL_TREE,
- build (MULT_EXPR, ret_type, m_acc, ret_var));
-
- tmp = create_tmp_var (ret_type, "acc_tmp");
- add_referenced_tmp_var (tmp);
+ retval = adjust_return_value_with_ops (MULT_EXPR, "mul_tmp", m_acc, retval,
+ gsi, GSI_SAME_STMT);
+ if (a)
+ retval = adjust_return_value_with_ops (PLUS_EXPR, "acc_tmp", a_acc, retval,
+ gsi, GSI_SAME_STMT);
+ gimple_return_set_retval (ret_stmt, retval);
+ update_stmt (ret_stmt);
+}
- var = make_ssa_name (tmp, stmt);
- TREE_OPERAND (stmt, 0) = var;
- bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
+/* Subtract COUNT and FREQUENCY from the basic block and it's
+ outgoing edge. */
+static void
+decrease_profile (basic_block bb, gcov_type count, int frequency)
+{
+ edge e;
+ bb->count -= count;
+ if (bb->count < 0)
+ bb->count = 0;
+ bb->frequency -= frequency;
+ if (bb->frequency < 0)
+ bb->frequency = 0;
+ if (!single_succ_p (bb))
+ {
+ gcc_assert (!EDGE_COUNT (bb->succs));
+ return;
}
- else
- var = ret_var;
+ e = single_succ_edge (bb);
+ e->count -= count;
+ if (e->count < 0)
+ e->count = 0;
+}
- if (a)
- {
- stmt = build (MODIFY_EXPR, ret_type, NULL_TREE,
- build (PLUS_EXPR, ret_type, a_acc, var));
+/* Returns true if argument PARAM of the tail recursive call needs to be copied
+ when the call is eliminated. */
- tmp = create_tmp_var (ret_type, "acc_tmp");
- add_referenced_tmp_var (tmp);
+static bool
+arg_needs_copy_p (tree param)
+{
+ tree def;
- var = make_ssa_name (tmp, stmt);
- TREE_OPERAND (stmt, 0) = var;
- bsi_insert_before (&bsi, stmt, BSI_NEW_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)
+ return false;
- TREE_OPERAND (ret_stmt, 0) = var;
- modify_stmt (ret_stmt);
+ return true;
}
/* Eliminates tail call described by T. TMP_VARS is a list of
static void
eliminate_tail_call (struct tailcall *t)
{
- tree param, stmt, args, rslt, call;
+ tree param, rslt;
+ gimple stmt, call;
+ tree arg;
+ size_t idx;
basic_block bb, first;
edge e;
- tree phi;
- stmt_ann_t ann;
- v_may_def_optype v_may_defs;
- unsigned i;
- block_stmt_iterator bsi;
+ gimple phi;
+ gimple_stmt_iterator gsi;
+ gimple orig_stmt;
- stmt = bsi_stmt (t->call_bsi);
- get_stmt_operands (stmt);
- ann = stmt_ann (stmt);
- bb = t->call_block;
+ stmt = orig_stmt = gsi_stmt (t->call_gsi);
+ bb = gsi_bb (t->call_gsi);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Eliminated tail recursion in bb %d : ",
bb->index);
- print_generic_stmt (dump_file, stmt, TDF_SLIM);
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
- if (TREE_CODE (stmt) == MODIFY_EXPR)
- stmt = TREE_OPERAND (stmt, 1);
+ gcc_assert (is_gimple_call (stmt));
- first = ENTRY_BLOCK_PTR->succ->dest;
+ first = single_succ (ENTRY_BLOCK_PTR);
- /* Remove the code after call_bsi that will become unreachable. The
+ /* Remove the code after call_gsi that will become unreachable. The
possibly unreachable code in other blocks is removed later in
cfg cleanup. */
- bsi = t->call_bsi;
- bsi_next (&bsi);
- while (!bsi_end_p (bsi))
+ gsi = t->call_gsi;
+ gsi_next (&gsi);
+ while (!gsi_end_p (gsi))
{
+ gimple t = gsi_stmt (gsi);
/* Do not remove the return statement, so that redirect_edge_and_branch
sees how the block ends. */
- if (TREE_CODE (bsi_stmt (bsi)) == RETURN_EXPR)
+ if (gimple_code (t) == GIMPLE_RETURN)
break;
- bsi_remove (&bsi);
+ gsi_remove (&gsi, true);
+ release_defs (t);
}
+ /* Number of executions of function has reduced by the tailcall. */
+ e = single_succ_edge (gsi_bb (t->call_gsi));
+ decrease_profile (EXIT_BLOCK_PTR, e->count, EDGE_FREQUENCY (e));
+ decrease_profile (ENTRY_BLOCK_PTR, e->count, EDGE_FREQUENCY (e));
+ if (e->dest != EXIT_BLOCK_PTR)
+ decrease_profile (e->dest, e->count, EDGE_FREQUENCY (e));
+
/* Replace the call by a jump to the start of function. */
- e = redirect_edge_and_branch (t->call_block->succ, first);
- if (!e)
- abort ();
- PENDING_STMT (e) = NULL_TREE;
-
- /* Add phi node entries for arguments. Not every PHI node corresponds to
- a function argument (there may be PHI nodes for virtual definitions of the
- eliminated calls), so we search for a PHI corresponding to each argument
- rather than searching for which argument a PHI node corresponds to. */
-
+ e = redirect_edge_and_branch (single_succ_edge (gsi_bb (t->call_gsi)),
+ first);
+ gcc_assert (e);
+ PENDING_STMT (e) = NULL;
+
+ /* Add phi node entries for arguments. The ordering of the phi nodes should
+ be the same as the ordering of the arguments. */
for (param = DECL_ARGUMENTS (current_function_decl),
- args = TREE_OPERAND (stmt, 1);
+ idx = 0, gsi = gsi_start_phis (first);
param;
- param = TREE_CHAIN (param),
- args = TREE_CHAIN (args))
+ param = TREE_CHAIN (param), idx++)
{
-
- for (phi = phi_nodes (first); phi; phi = PHI_CHAIN (phi))
- if (param == SSA_NAME_VAR (PHI_RESULT (phi)))
- break;
-
- /* The phi node indeed does not have to be there, in case the operand is
- invariant in the function. */
- if (!phi)
+ if (!arg_needs_copy_p (param))
continue;
- add_phi_arg (&phi, TREE_VALUE (args), e);
- }
-
- /* Add phi nodes for the call clobbered variables. */
- v_may_defs = V_MAY_DEF_OPS (ann);
- for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
- {
- param = SSA_NAME_VAR (V_MAY_DEF_RESULT (v_may_defs, i));
- for (phi = phi_nodes (first); phi; phi = PHI_CHAIN (phi))
- if (param == SSA_NAME_VAR (PHI_RESULT (phi)))
- break;
-
- if (!phi)
- {
- tree name = var_ann (param)->default_def;
- tree new_name;
-
- if (!name)
- {
- /* It may happen that the tag does not have a default_def in case
- when all uses of it are dominated by a MUST_DEF. This however
- means that it is not necessary to add a phi node for this
- tag. */
- continue;
- }
- new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name));
-
- var_ann (param)->default_def = new_name;
- phi = create_phi_node (name, first);
- SSA_NAME_DEF_STMT (name) = phi;
- add_phi_arg (&phi, new_name, ENTRY_BLOCK_PTR->succ);
-
- /* For all calls the same set of variables should be clobbered. This
- means that there always should be the appropriate phi node except
- for the first time we eliminate the call. */
- if (first->pred->pred_next->pred_next)
- abort ();
- }
+ arg = gimple_call_arg (stmt, idx);
+ phi = gsi_stmt (gsi);
+ gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi)));
- add_phi_arg (&phi, V_MAY_DEF_OP (v_may_defs, i), e);
+ add_phi_arg (phi, arg, e, gimple_location (stmt));
+ gsi_next (&gsi);
}
/* Update the values of accumulators. */
- adjust_accumulator_values (t->call_bsi, t->mult, t->add, e);
+ adjust_accumulator_values (t->call_gsi, t->mult, t->add, e);
- call = bsi_stmt (t->call_bsi);
- if (TREE_CODE (call) == MODIFY_EXPR)
+ call = gsi_stmt (t->call_gsi);
+ rslt = gimple_call_lhs (call);
+ if (rslt != NULL_TREE)
{
- rslt = TREE_OPERAND (call, 0);
-
/* Result of the call will no longer be defined. So adjust the
SSA_NAME_DEF_STMT accordingly. */
- SSA_NAME_DEF_STMT (rslt) = build_empty_stmt ();
+ SSA_NAME_DEF_STMT (rslt) = gimple_build_nop ();
}
- bsi_remove (&t->call_bsi);
+ gsi_remove (&t->call_gsi, true);
+ release_defs (call);
+}
+
+/* Add phi nodes for the virtual operands defined in the function to the
+ header of the loop created by tail recursion elimination.
+
+ Originally, we used to add phi nodes only for call clobbered variables,
+ as the value of the non-call clobbered ones obviously cannot be used
+ or changed within the recursive call. However, the local variables
+ from multiple calls now share the same location, so the virtual ssa form
+ requires us to say that the location dies on further iterations of the loop,
+ which requires adding phi nodes.
+*/
+static void
+add_virtual_phis (void)
+{
+ referenced_var_iterator rvi;
+ tree var;
+
+ /* The problematic part is that there is no way how to know what
+ to put into phi nodes (there in fact does not have to be such
+ ssa name available). A solution would be to have an artificial
+ use/kill for all virtual operands in EXIT node. Unless we have
+ 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)
+ {
+ if (!is_gimple_reg (var) && gimple_default_def (cfun, var) != NULL_TREE)
+ mark_sym_for_renaming (var);
+ }
}
/* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also
if (opt_tailcalls)
{
- tree stmt = bsi_stmt (t->call_bsi);
+ gimple stmt = gsi_stmt (t->call_gsi);
- stmt = get_call_expr_in (stmt);
- CALL_EXPR_TAILCALL (stmt) = 1;
+ gimple_call_set_tail (stmt, true);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Found tail call ");
- print_generic_expr (dump_file, stmt, dump_flags);
- fprintf (dump_file, " in bb %i\n", t->call_block->index);
+ print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+ fprintf (dump_file, " in bb %i\n", (gsi_bb (t->call_gsi))->index);
}
}
return false;
}
+/* Creates a tail-call accumulator of the same type as the return type of the
+ current function. LABEL is the name used to creating the temporary
+ variable for the accumulator. The accumulator will be inserted in the
+ phis of a basic block BB with single predecessor with an initial value
+ INIT converted to the current function return type. */
+
+static tree
+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);
+ gimple phi;
+
+ if (TREE_CODE (ret_type) == COMPLEX_TYPE
+ || TREE_CODE (ret_type) == VECTOR_TYPE)
+ DECL_GIMPLE_REG_P (tmp) = 1;
+ 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),
+ UNKNOWN_LOCATION);
+ return PHI_RESULT (phi);
+}
+
/* Optimizes tail calls in the function, turning the tail recursion
into iteration. */
-static void
+static unsigned int
tree_optimize_tail_calls_1 (bool opt_tailcalls)
{
edge e;
bool phis_constructed = false;
struct tailcall *tailcalls = NULL, *act, *next;
bool changed = false;
- basic_block first = ENTRY_BLOCK_PTR->succ->dest;
- tree stmt, param, ret_type, tmp, phi;
+ basic_block first = single_succ (ENTRY_BLOCK_PTR);
+ tree param;
+ gimple stmt;
+ edge_iterator ei;
if (!suitable_for_tail_opt_p ())
- return;
+ return 0;
if (opt_tailcalls)
opt_tailcalls = suitable_for_tail_call_opt_p ();
- for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next)
+ FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
{
/* Only traverse the normal exits, i.e. those that end with return
statement. */
stmt = last_stmt (e->src);
if (stmt
- && TREE_CODE (stmt) == RETURN_EXPR)
+ && gimple_code (stmt) == GIMPLE_RETURN)
find_tail_calls (e->src, &tailcalls);
}
if (!phis_constructed)
{
- /* Ensure that there is only one predecessor of the block. */
- if (first->pred->pred_next)
- first = split_edge (ENTRY_BLOCK_PTR->succ);
+ /* Ensure that there is only one predecessor of the block
+ or if there are existing degenerate PHI nodes. */
+ if (!single_pred_p (first)
+ || !gimple_seq_empty_p (phi_nodes (first)))
+ first = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
/* Copy the args if needed. */
for (param = DECL_ARGUMENTS (current_function_decl);
param;
param = TREE_CHAIN (param))
- if (var_ann (param)
- /* Also parameters that are only defined but never used need not
- be copied. */
- && (var_ann (param)->default_def
- && TREE_CODE (var_ann (param)->default_def) == SSA_NAME))
- {
- tree name = var_ann (param)->default_def;
- tree new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name));
- tree phi;
-
- var_ann (param)->default_def = new_name;
- phi = create_phi_node (name, first);
- SSA_NAME_DEF_STMT (name) = phi;
- add_phi_arg (&phi, new_name, first->pred);
- }
+ if (arg_needs_copy_p (param))
+ {
+ tree name = gimple_default_def (cfun, param);
+ tree new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name));
+ gimple phi;
+
+ 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),
+ EXPR_LOCATION (param));
+ }
phis_constructed = true;
}
if (act->add && !a_acc)
- {
- ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
-
- tmp = create_tmp_var (ret_type, "add_acc");
- add_referenced_tmp_var (tmp);
-
- phi = create_phi_node (tmp, first);
- add_phi_arg (&phi, build_int_cst (ret_type, 0), first->pred);
- a_acc = PHI_RESULT (phi);
- }
+ a_acc = create_tailcall_accumulator ("add_acc", first,
+ integer_zero_node);
if (act->mult && !m_acc)
- {
- ret_type = TREE_TYPE (DECL_RESULT (current_function_decl));
-
- tmp = create_tmp_var (ret_type, "mult_acc");
- add_referenced_tmp_var (tmp);
-
- phi = create_phi_node (tmp, first);
- add_phi_arg (&phi, build_int_cst (ret_type, 1), first->pred);
- m_acc = PHI_RESULT (phi);
- }
+ m_acc = create_tailcall_accumulator ("mult_acc", first,
+ integer_one_node);
}
for (; tailcalls; tailcalls = next)
if (a_acc || m_acc)
{
/* Modify the remaining return statements. */
- for (e = EXIT_BLOCK_PTR->pred; e; e = e->pred_next)
+ FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
{
stmt = last_stmt (e->src);
if (stmt
- && TREE_CODE (stmt) == RETURN_EXPR)
+ && gimple_code (stmt) == GIMPLE_RETURN)
adjust_return_value (e->src, m_acc, a_acc);
}
}
if (changed)
- {
- free_dominance_info (CDI_DOMINATORS);
- cleanup_tree_cfg ();
- }
+ free_dominance_info (CDI_DOMINATORS);
+
+ if (phis_constructed)
+ add_virtual_phis ();
+ if (changed)
+ return TODO_cleanup_cfg | TODO_update_ssa_only_virtuals;
+ return 0;
}
-static void
+static unsigned int
execute_tail_recursion (void)
{
- tree_optimize_tail_calls_1 (false);
+ return tree_optimize_tail_calls_1 (false);
}
static bool
gate_tail_calls (void)
{
- return flag_optimize_sibling_calls != 0;
+ return flag_optimize_sibling_calls != 0 && dbg_cnt (tail_call);
}
-static void
+static unsigned int
execute_tail_calls (void)
{
- tree_optimize_tail_calls_1 (true);
+ return tree_optimize_tail_calls_1 (true);
}
-struct tree_opt_pass pass_tail_recursion =
+struct gimple_opt_pass pass_tail_recursion =
{
+ {
+ GIMPLE_PASS,
"tailr", /* name */
- NULL, /* gate */
+ gate_tail_calls, /* gate */
execute_tail_recursion, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
- 0, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ TV_NONE, /* tv_id */
+ 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 */
- 0 /* letter */
+ TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ }
};
-struct tree_opt_pass pass_tail_calls =
+struct gimple_opt_pass pass_tail_calls =
{
+ {
+ GIMPLE_PASS,
"tailc", /* name */
gate_tail_calls, /* gate */
execute_tail_calls, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
- 0, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ TV_NONE, /* tv_id */
+ 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 */
- 0 /* letter */
+ TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ }
};
OSDN Git Service
