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Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/tree-tailcall.c')
| -rw-r--r-- | gcc-4.2.1-5666.3/gcc/tree-tailcall.c | 1049 |
1 files changed, 1049 insertions, 0 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/tree-tailcall.c b/gcc-4.2.1-5666.3/gcc/tree-tailcall.c new file mode 100644 index 000000000..e45f0be35 --- /dev/null +++ b/gcc-4.2.1-5666.3/gcc/tree-tailcall.c @@ -0,0 +1,1049 @@ +/* Tail call optimization on trees. + Copyright (C) 2003, 2004, 2005 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) +any later version. + +GCC is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +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. */ + +#include "config.h" +#include "system.h" +#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 "except.h" +#include "tree-pass.h" +#include "flags.h" +#include "langhooks.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 + where they are used for sibcall optimization. + + In addition to the standard tail recursion elimination, we handle the most + trivial cases of making the call tail recursive by creating accumulators. + For example the following function + + int sum (int n) + { + if (n > 0) + return n + sum (n - 1); + else + return 0; + } + + is transformed into + + int sum (int n) + { + int acc = 0; + + while (n > 0) + acc += n--; + + return acc; + } + + 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 + guaranteed that the value of the accumulator never change, we + omit the accumulator. + + There are three cases how the function may exit. The first one is + handled in adjust_return_value, the other two in adjust_accumulator_values + (the second case is actually a special case of the third one and we + present it separately just for clarity): + + 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 + + a_acc + (a + m * f(...)) * m_acc = (a_acc + a * m_acc) + (m * m_acc) * f(...). + + I.e. we increase a_acc by a * m_acc, multiply m_acc by m and + eliminate the tail call to f. Special cases when the value is just + added or just multiplied are obtained by setting a = 0 or m = 1. + + TODO -- it is possible to do similar tricks for other operations. */ + +/* A structure that describes the tailcall. */ + +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; + + /* True if it is a call to the current function. */ + bool tail_recursion; + + /* The return value of the caller is mult * f + add, where f is the return + value of the call. */ + tree mult, add; + + /* Next tailcall in the chain. */ + struct tailcall *next; +}; + +/* The variables holding the value of multiplicative and additive + accumulator. */ +static tree m_acc, a_acc; + +static bool suitable_for_tail_opt_p (void); +static bool optimize_tail_call (struct tailcall *, bool); +static void eliminate_tail_call (struct tailcall *); +static void find_tail_calls (basic_block, struct tailcall **); + +/* Returns false when the function is not suitable for tail call optimization + from some reason (e.g. if it takes variable number of arguments). */ + +static bool +suitable_for_tail_opt_p (void) +{ + referenced_var_iterator rvi; + tree var; + + if (current_function_stdarg) + return false; + + /* No local variable nor structure field should be call-clobbered. We + ignore any kind of memory tag, as these are not real variables. */ + + FOR_EACH_REFERENCED_VAR (var, rvi) + { + + if (!is_global_var (var) + && (!MTAG_P (var) || TREE_CODE (var) == STRUCT_FIELD_TAG) + && is_call_clobbered (var)) + return false; + } + + return true; +} +/* Returns false when the function is not suitable for tail call optimization + from some reason (e.g. if it takes variable number of arguments). + This test must pass in addition to suitable_for_tail_opt_p in order to make + tail call discovery happen. */ + +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) + return false; + + /* 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 ()) + return false; + + /* 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) + 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 to 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 + basic blocks that have only single successor. Returns the expression + containing the value of EXPR at BSI. */ + +static tree +independent_of_stmt_p (tree expr, tree at, block_stmt_iterator bsi) +{ + basic_block bb, call_bb, at_bb; + edge e; + edge_iterator ei; + + if (is_gimple_min_invariant (expr)) + return expr; + + if (TREE_CODE (expr) != SSA_NAME) + 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 = single_succ (bb)) + bb->aux = &bb->aux; + bb->aux = &bb->aux; + + while (1) + { + at = SSA_NAME_DEF_STMT (expr); + bb = bb_for_stmt (at); + + /* The default definition or defined before the chain. */ + if (!bb || !bb->aux) + break; + + if (bb == call_bb) + { + for (; !bsi_end_p (bsi); bsi_next (&bsi)) + if (bsi_stmt (bsi) == at) + break; + + if (!bsi_end_p (bsi)) + expr = NULL_TREE; + break; + } + + if (TREE_CODE (at) != PHI_NODE) + { + expr = NULL_TREE; + break; + } + + FOR_EACH_EDGE (e, ei, bb->preds) + if (e->src->aux) + break; + gcc_assert (e); + + expr = PHI_ARG_DEF_FROM_EDGE (at, e); + if (TREE_CODE (expr) != SSA_NAME) + { + /* The value is a constant. */ + break; + } + } + + /* Unmark the blocks. */ + 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. */ + +static bool +process_assignment (tree ass, tree stmt, block_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; + + /* 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 (src_var != *ass_var) + return false; + + *ass_var = dest; + return true; + } + + if (TREE_CODE_CLASS (code) != tcc_binary) + 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_unsafe_math_optimizations) + 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 = TREE_OPERAND (src, 0); + op1 = TREE_OPERAND (src, 1); + + if (op0 == *ass_var + && (non_ass_var = independent_of_stmt_p (op1, stmt, call))) + ; + else if (op1 == *ass_var + && (non_ass_var = independent_of_stmt_p (op0, stmt, call))) + ; + else + return false; + + 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). */ + + default: + return false; + } +} + +/* Propagate VAR through phis on edge E. */ + +static tree +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); + + return var; +} + +/* Finds tailcalls falling into basic block BB. The list of found tailcalls is + added to the start of RET. */ + +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; + bool tail_recursion; + struct tailcall *nw; + edge e; + tree m, a; + basic_block abb; + stmt_ann_t ann; + + if (!single_succ_p (bb)) + return; + + for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi)) + { + stmt = bsi_stmt (bsi); + + /* Ignore labels. */ + if (TREE_CODE (stmt) == LABEL_EXPR) + continue; + + /* Check for a call. */ + if (TREE_CODE (stmt) == MODIFY_EXPR) + { + 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; + } + + if (TREE_CODE (call) == CALL_EXPR) + break; + + /* If the statement has virtual or volatile operands, fail. */ + ann = stmt_ann (stmt); + if (!ZERO_SSA_OPERANDS (stmt, (SSA_OP_VUSE | SSA_OP_VIRTUAL_DEFS)) + || ann->has_volatile_ops) + return; + } + + if (bsi_end_p (bsi)) + { + edge_iterator ei; + /* Recurse to the predecessors. */ + FOR_EACH_EDGE (e, ei, bb->preds) + find_tail_calls (e->src, ret); + + return; + } + + /* We found the call, check whether it is suitable. */ + tail_recursion = false; + func = get_callee_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 = TREE_VALUE (args); + 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. */ + if (!is_gimple_reg_type (TREE_TYPE (param)) + || !lang_hooks.types_compatible_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 MODIFY_EXPR and + updating the virtual operands). */ + if (!is_gimple_reg (param)) + break; + } + } + if (!args && !param) + tail_recursion = true; + } + + /* 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, + since we are running after dce. */ + m = NULL_TREE; + a = NULL_TREE; + + abb = bb; + absi = bsi; + while (1) + { + bsi_next (&absi); + + while (bsi_end_p (absi)) + { + ass_var = propagate_through_phis (ass_var, single_succ_edge (abb)); + abb = single_succ (abb); + absi = bsi_start (abb); + } + + stmt = bsi_stmt (absi); + + if (TREE_CODE (stmt) == LABEL_EXPR) + continue; + + if (TREE_CODE (stmt) == RETURN_EXPR) + break; + + if (TREE_CODE (stmt) != MODIFY_EXPR) + return; + + if (!process_assignment (stmt, stmt, bsi, &m, &a, &ass_var)) + 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) + return; + + if (!process_assignment (ret_var, stmt, bsi, &m, &a, &ass_var)) + return; + ret_var = TREE_OPERAND (ret_var, 0); + } + + /* We may proceed if there either is no return value, or the return value + is identical to the call's return. */ + if (ret_var + && (ret_var != ass_var)) + return; + + /* If this is not a tail recursive call, we cannot handle addends or + multiplicands. */ + if (!tail_recursion && (m || a)) + return; + + nw = XNEW (struct tailcall); + + nw->call_block = bb; + nw->call_bsi = bsi; + + nw->tail_recursion = tail_recursion; + + nw->mult = m; + nw->add = a; + + nw->next = *ret; + *ret = nw; +} + +/* Adjust the accumulator values according to A and M after BSI, and update + the phi nodes on edge BACK. */ + +static void +adjust_accumulator_values (block_stmt_iterator bsi, tree m, tree a, edge back) +{ + 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; + + if (a) + { + if (m_acc) + { + if (integer_onep (a)) + var = m_acc; + else + { + stmt = build2 (MODIFY_EXPR, ret_type, NULL_TREE, + build2 (MULT_EXPR, ret_type, m_acc, a)); + + tmp = create_tmp_var (ret_type, "acc_tmp"); + add_referenced_var (tmp); + + var = make_ssa_name (tmp, stmt); + TREE_OPERAND (stmt, 0) = var; + bsi_insert_after (&bsi, stmt, BSI_NEW_STMT); + } + } + else + var = a; + + stmt = build2 (MODIFY_EXPR, ret_type, NULL_TREE, + build2 (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; + } + + if (m) + { + stmt = build2 (MODIFY_EXPR, ret_type, NULL_TREE, + build2 (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; + } + + 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); + } + + 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); + } +} + +/* Adjust value of the return at the end of BB according to M and A + accumulators. */ + +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); + + gcc_assert (TREE_CODE (ret_stmt) == RETURN_EXPR); + + ret_var = TREE_OPERAND (ret_stmt, 0); + if (!ret_var) + 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 = build2 (MODIFY_EXPR, ret_type, NULL_TREE, + build2 (MULT_EXPR, ret_type, m_acc, ret_var)); + + tmp = create_tmp_var (ret_type, "acc_tmp"); + add_referenced_var (tmp); + + var = make_ssa_name (tmp, stmt); + TREE_OPERAND (stmt, 0) = var; + bsi_insert_before (&bsi, stmt, BSI_SAME_STMT); + } + else + var = ret_var; + + if (a) + { + stmt = build2 (MODIFY_EXPR, ret_type, NULL_TREE, + build2 (PLUS_EXPR, ret_type, a_acc, var)); + + tmp = create_tmp_var (ret_type, "acc_tmp"); + add_referenced_var (tmp); + + var = make_ssa_name (tmp, stmt); + TREE_OPERAND (stmt, 0) = var; + bsi_insert_before (&bsi, stmt, BSI_SAME_STMT); + } + + TREE_OPERAND (ret_stmt, 0) = var; + update_stmt (ret_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; + } + e = single_succ_edge (bb); + e->count -= count; + if (e->count < 0) + e->count = 0; +} + +/* Returns true if argument PARAM of the tail recursive call needs to be copied + when the call is eliminated. */ + +static bool +arg_needs_copy_p (tree param) +{ + tree def; + + if (!is_gimple_reg (param) || !var_ann (param)) + return false; + + /* Parameters that are only defined but never used need not be copied. */ + def = default_def (param); + if (!def) + return false; + + return true; +} + +/* Eliminates tail call described by T. TMP_VARS is a list of + temporary variables used to copy the function arguments. */ + +static void +eliminate_tail_call (struct tailcall *t) +{ + tree param, stmt, args, rslt, call; + basic_block bb, first; + edge e; + tree phi; + block_stmt_iterator bsi; + tree orig_stmt; + + stmt = orig_stmt = bsi_stmt (t->call_bsi); + bb = t->call_block; + + 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); + fprintf (dump_file, "\n"); + } + + if (TREE_CODE (stmt) == MODIFY_EXPR) + stmt = TREE_OPERAND (stmt, 1); + + first = single_succ (ENTRY_BLOCK_PTR); + + /* Remove the code after call_bsi 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)) + { + tree t = bsi_stmt (bsi); + /* Do not remove the return statement, so that redirect_edge_and_branch + sees how the block ends. */ + if (TREE_CODE (t) == RETURN_EXPR) + break; + + bsi_remove (&bsi, true); + release_defs (t); + } + + /* Number of executions of function has reduced by the tailcall. */ + e = single_succ_edge (t->call_block); + 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 (single_succ_edge (t->call_block), first); + gcc_assert (e); + PENDING_STMT (e) = NULL_TREE; + + /* 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), + phi = phi_nodes (first); + param; + param = TREE_CHAIN (param), + args = TREE_CHAIN (args)) + { + if (!arg_needs_copy_p (param)) + continue; + gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi))); + + add_phi_arg (phi, TREE_VALUE (args), e); + phi = PHI_CHAIN (phi); + } + + /* Update the values of accumulators. */ + adjust_accumulator_values (t->call_bsi, t->mult, t->add, e); + + call = bsi_stmt (t->call_bsi); + if (TREE_CODE (call) == MODIFY_EXPR) + { + 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 (); + } + + bsi_remove (&t->call_bsi, 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) && default_def (var) != NULL_TREE) + mark_sym_for_renaming (var); + } + + update_ssa (TODO_update_ssa_only_virtuals); +} + +/* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also + mark the tailcalls for the sibcall optimization. */ + +static bool +optimize_tail_call (struct tailcall *t, bool opt_tailcalls) +{ + if (t->tail_recursion) + { + eliminate_tail_call (t); + return true; + } + + if (opt_tailcalls) + { + tree stmt = bsi_stmt (t->call_bsi); + + stmt = get_call_expr_in (stmt); + CALL_EXPR_TAILCALL (stmt) = 1; + 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); + } + } + + return false; +} + +/* Optimizes tail calls in the function, turning the tail recursion + into iteration. */ + +static void +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 = single_succ (ENTRY_BLOCK_PTR); + tree stmt, param, ret_type, tmp, phi; + edge_iterator ei; + + if (!suitable_for_tail_opt_p ()) + return; + if (opt_tailcalls) + opt_tailcalls = suitable_for_tail_call_opt_p (); + + 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) + find_tail_calls (e->src, &tailcalls); + } + + /* Construct the phi nodes and accumulators if necessary. */ + a_acc = m_acc = NULL_TREE; + for (act = tailcalls; act; act = act->next) + { + if (!act->tail_recursion) + continue; + + if (!phis_constructed) + { + /* Ensure that there is only one predecessor of the block. */ + if (!single_pred_p (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 (arg_needs_copy_p (param)) + { + tree name = default_def (param); + tree new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name)); + tree 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)); + } + 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_var (tmp); + + phi = create_phi_node (tmp, first); + add_phi_arg (phi, + /* RET_TYPE can be a float when -ffast-maths is + enabled. */ + fold_convert (ret_type, integer_zero_node), + single_pred_edge (first)); + a_acc = PHI_RESULT (phi); + } + + if (act->mult && !m_acc) + { + ret_type = TREE_TYPE (DECL_RESULT (current_function_decl)); + + tmp = create_tmp_var (ret_type, "mult_acc"); + add_referenced_var (tmp); + + phi = create_phi_node (tmp, first); + add_phi_arg (phi, + /* RET_TYPE can be a float when -ffast-maths is + enabled. */ + fold_convert (ret_type, integer_one_node), + single_pred_edge (first)); + m_acc = PHI_RESULT (phi); + } + } + + + if (phis_constructed) + { + /* Reverse the order of the phi nodes, so that it matches the order + of operands of the function, as assumed by eliminate_tail_call. */ + set_phi_nodes (first, phi_reverse (phi_nodes (first))); + } + + for (; tailcalls; tailcalls = next) + { + next = tailcalls->next; + changed |= optimize_tail_call (tailcalls, opt_tailcalls); + free (tailcalls); + } + + if (a_acc || m_acc) + { + /* Modify the remaining return statements. */ + FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) + { + stmt = last_stmt (e->src); + + if (stmt + && TREE_CODE (stmt) == RETURN_EXPR) + adjust_return_value (e->src, m_acc, a_acc); + } + } + + if (changed) + { + free_dominance_info (CDI_DOMINATORS); + cleanup_tree_cfg (); + } + + if (phis_constructed) + add_virtual_phis (); +} + +static unsigned int +execute_tail_recursion (void) +{ + tree_optimize_tail_calls_1 (false); + return 0; +} + +static bool +gate_tail_calls (void) +{ + return flag_optimize_sibling_calls != 0; +} + +static unsigned int +execute_tail_calls (void) +{ + tree_optimize_tail_calls_1 (true); + return 0; +} + +struct tree_opt_pass pass_tail_recursion = +{ + "tailr", /* name */ + 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 */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */ + 0 /* letter */ +}; + +struct tree_opt_pass pass_tail_calls = +{ + "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 */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */ + 0 /* letter */ +}; |