| /* 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, 59 Temple Place - Suite 330, |
| Boston, MA 02111-1307, 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) |
| { |
| int i; |
| |
| if (current_function_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++) |
| { |
| 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)) |
| 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 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 = EDGE_SUCC (bb, 0)->dest) |
| 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 = EDGE_SUCC (bb, 0)->dest) |
| 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 (EDGE_COUNT (bb->succs) > 1) |
| 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; |
| |
| get_stmt_operands (stmt); |
| |
| /* 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 (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) |
| 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, EDGE_SUCC (abb, 0)); |
| abb = EDGE_SUCC (abb, 0)->dest; |
| 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 = xmalloc (sizeof (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 = 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); |
| } |
| } |
| 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; |
| } |
| |
| 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; |
| } |
| |
| 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 = 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); |
| |
| 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 = build (MODIFY_EXPR, ret_type, NULL_TREE, |
| build (PLUS_EXPR, ret_type, a_acc, var)); |
| |
| 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_before (&bsi, stmt, BSI_SAME_STMT); |
| } |
| |
| TREE_OPERAND (ret_stmt, 0) = var; |
| modify_stmt (ret_stmt); |
| } |
| |
| /* 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; |
| stmt_ann_t ann; |
| v_may_def_optype v_may_defs; |
| unsigned i; |
| block_stmt_iterator bsi; |
| |
| stmt = bsi_stmt (t->call_bsi); |
| get_stmt_operands (stmt); |
| ann = stmt_ann (stmt); |
| 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 = EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest; |
| |
| /* 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); |
| release_defs (t); |
| } |
| |
| /* Replace the call by a jump to the start of function. */ |
| e = redirect_edge_and_branch (EDGE_SUCC (t->call_block, 0), first); |
| gcc_assert (e); |
| 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. */ |
| |
| for (param = DECL_ARGUMENTS (current_function_decl), |
| args = TREE_OPERAND (stmt, 1); |
| param; |
| param = TREE_CHAIN (param), |
| args = TREE_CHAIN (args)) |
| { |
| |
| 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) |
| 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, EDGE_SUCC (ENTRY_BLOCK_PTR, 0)); |
| |
| /* 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. */ |
| gcc_assert (EDGE_COUNT (first->preds) <= 2); |
| } |
| |
| add_phi_arg (phi, V_MAY_DEF_OP (v_may_defs, i), e); |
| } |
| |
| /* 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); |
| release_defs (call); |
| } |
| |
| /* 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 = EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest; |
| 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 (EDGE_COUNT (first->preds) > 1) |
| first = split_edge (EDGE_SUCC (ENTRY_BLOCK_PTR, 0)); |
| |
| /* Copy the args if needed. */ |
| for (param = DECL_ARGUMENTS (current_function_decl); |
| param; |
| param = TREE_CHAIN (param)) |
| if (is_gimple_reg (param) |
| && 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, EDGE_PRED (first, 0)); |
| } |
| 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, |
| /* RET_TYPE can be a float when -ffast-maths is |
| enabled. */ |
| fold_convert (ret_type, integer_zero_node), |
| EDGE_PRED (first, 0)); |
| 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_tmp_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), |
| EDGE_PRED (first, 0)); |
| m_acc = PHI_RESULT (phi); |
| } |
| } |
| |
| 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 (); |
| } |
| } |
| |
| static void |
| execute_tail_recursion (void) |
| { |
| tree_optimize_tail_calls_1 (false); |
| } |
| |
| static bool |
| gate_tail_calls (void) |
| { |
| return flag_optimize_sibling_calls != 0; |
| } |
| |
| static void |
| execute_tail_calls (void) |
| { |
| tree_optimize_tail_calls_1 (true); |
| } |
| |
| struct tree_opt_pass pass_tail_recursion = |
| { |
| "tailr", /* name */ |
| NULL, /* 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 */ |
| }; |