diff options
Diffstat (limited to 'gcc/tree-ssa-phiopt.c')
| -rw-r--r-- | gcc/tree-ssa-phiopt.c | 631 |
1 files changed, 618 insertions, 13 deletions
diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c index 9bcb7144a50..0b329ea038d 100644 --- a/gcc/tree-ssa-phiopt.c +++ b/gcc/tree-ssa-phiopt.c @@ -25,6 +25,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA #include "errors.h" #include "ggc.h" #include "tree.h" +#include "flags.h" #include "rtl.h" #include "tm_p.h" #include "basic-block.h" @@ -38,7 +39,22 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA static void tree_ssa_phiopt (void); static bool conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1); +static bool absolute_replacement (basic_block bb, tree phi, tree arg0, + tree arg1); +static bool value_replacement (basic_block bb, tree phi, tree arg0, + tree arg1); + + +/* Build a temporary. Make sure and register it to be renamed. */ +static tree +make_temp (tree type) +{ + tree t = create_tmp_var (type, NULL); + add_referenced_tmp_var (t); + bitmap_set_bit (vars_to_rename, var_ann (t)->uid); + return t; +} /* This pass eliminates PHI nodes which can be trivially implemented as an assignment from a conditional expression. ie if we have something @@ -59,7 +75,48 @@ static bool conditional_replacement (basic_block bb, tree phi, tree arg0, bb1 will become unreachable and bb0 and bb2 will almost always be merged into a single block. This occurs often due to gimplification - of conditionals. */ + of conditionals. + + Also this pass eliminates PHI nodes which are really absolute values. ie + if we have something like: + + bb0: + if (a >= 0) goto bb2; else goto bb1; + bb1: + x = -a; + bb2: + x = PHI (x (bb1), a (bb0)); + + We can rewrite that as: + + bb0: + bb1: + bb2: + x = ABS_EXPR< a >; + + bb1 will become unreachable and bb0 and bb2 will almost always be merged + into a single block. This occurs because fold never had dected then in + the first place, note this these are all done already by the ifcvt + optimization on the RTL level. + + Also done is the following optimization: + + bb0: + if (a != b) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI (a (bb1), b (bb0)) + + We can rewrite that as: + + bb0: + bb1: + bb2: + x = b; + + This occurs when people are doing error checking or when optimizers + are doing its job. Note this is also done already by ifcvt optimizer + on the RTL level. */ static void tree_ssa_phiopt (void) @@ -86,10 +143,29 @@ tree_ssa_phiopt (void) /* Do the replacement of conditional if it can be done. */ if (conditional_replacement (bb, phi, arg0, arg1)) { - /* We have done the replacement so we need to rebuild the cfg. */ + /* We have done the replacement so we need to rebuild the + cfg and cannot do any more. */ removed_phis = true; continue; } + + /* Do the replacement for absolute if it can be done. */ + if (absolute_replacement (bb, phi, arg0, arg1)) + { + /* We have done the replacement so we need to rebuild the + cfg and cannot do any more. */ + removed_phis = true; + continue; + } + + /* Do the replacement for value if it can be done. */ + if (value_replacement (bb, phi, arg0, arg1)) + { + /* We have done the replacement so we need to rebuild the + cfg and cannot do any more. */ + removed_phis = true; + continue; + } } } @@ -108,11 +184,13 @@ static bool conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) { tree result; + tree old_result = NULL; basic_block other_block = NULL; basic_block cond_block = NULL; tree last0, last1, new, cond; block_stmt_iterator bsi; edge true_edge, false_edge; + tree new_var = NULL; /* The PHI arguments have the constants 0 and 1, then convert it to the conditional. */ @@ -174,22 +252,46 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) /* If the condition is not a naked SSA_NAME and its type does not match the type of the result, then we can not optimize this case as it would likely create non-gimple code when the condition - was converted to the result's type. */ + so we create a new variable for it. */ cond = COND_EXPR_COND (last_stmt (cond_block)); result = PHI_RESULT (phi); if (TREE_CODE (cond) != SSA_NAME - && !lang_hooks.types_compatible_p (TREE_TYPE (cond), TREE_TYPE (result))) - return false; + && (TYPE_MAIN_VARIANT (TREE_TYPE (cond)) + != TYPE_MAIN_VARIANT (TREE_TYPE (result)))) + { + /* FIXME: disabled for now as the check for non-gimple is too + weak and will not find some cases. */ + return false; +#if 0 + new_var = make_temp (TREE_TYPE (cond)); + old_result = cond; + cond = new_var; +#endif + } /* If the condition was a naked SSA_NAME and the type is not the same as the type of the result, then convert the type of the condition. */ - if (!lang_hooks.types_compatible_p (TREE_TYPE (cond), TREE_TYPE (result))) + if (TYPE_MAIN_VARIANT (TREE_TYPE (cond)) + != TYPE_MAIN_VARIANT (TREE_TYPE (result))) cond = convert (TREE_TYPE (result), cond); /* We need to know which is the true edge and which is the false edge so that we know when to invert the condition below. */ extract_true_false_edges_from_block (cond_block, &true_edge, &false_edge); + + /* Insert our new statement at the head of our block. */ + bsi = bsi_start (bb); + + if (old_result) + { + tree new1; + new1 = convert (TREE_TYPE (result), old_result); + new1 = build (MODIFY_EXPR, TREE_TYPE (result), + new_var, new1); + bsi_insert_after (&bsi, new1, BSI_NEW_STMT); + } + /* At this point we know we have a COND_EXPR with two successors. One successor is BB, the other successor is an empty block which @@ -208,6 +310,7 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) false edge as the value zero. Note that those conditions are not the same since only one of the outgoing edges from the COND_EXPR will directly reach BB and thus be associated with an argument. */ + if ((PHI_ARG_EDGE (phi, 0) == true_edge && integer_onep (arg0)) || (PHI_ARG_EDGE (phi, 0) == false_edge && integer_zerop (arg0)) || (PHI_ARG_EDGE (phi, 1) == true_edge && integer_onep (arg1)) @@ -218,19 +321,31 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) } else { - cond = invert_truthvalue (cond); - + tree cond1 = invert_truthvalue (cond); + + cond = cond1; + + /* If what we get back is not gimple try to create it as gimple by + using a temporary variable. */ if (is_gimple_cast (cond) && !is_gimple_val (TREE_OPERAND (cond, 0))) - return false; + { + return false; + /* FIXME: disabled for now as it causes a bootstrap failure. */ +#if 0 + tree temp = TREE_OPERAND (cond, 0); + tree new_var_1 = make_temp (TREE_TYPE (temp)); + new = build (MODIFY_EXPR, TREE_TYPE (new_var_1), new_var_1, temp); + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + cond = convert (TREE_TYPE (result), new_var_1); +#endif + } new = build (MODIFY_EXPR, TREE_TYPE (PHI_RESULT (phi)), PHI_RESULT (phi), cond); } - /* Insert our new statement at the head of our block. */ - bsi = bsi_start (bb); - bsi_insert_after (&bsi, new, BSI_SAME_STMT); + bsi_insert_after (&bsi, new, BSI_NEW_STMT); /* Register our new statement as the defining statement for the result. */ @@ -274,6 +389,495 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) } +/* The function absolute_replacement does the main work of doing the absolute + replacement. Return true if the replacement is done. Otherwise return false. + bb is the basic block where the replacement is going to be done on. arg0 + is argument 0 from the phi. Likewise for arg1. */ +static bool +absolute_replacement (basic_block bb, tree phi, tree arg0, tree arg1) +{ + tree result; + basic_block other_block = NULL; + basic_block cond_block = NULL; + tree last0, last1, new, cond; + block_stmt_iterator bsi; + edge true_edge, false_edge; + tree asign = NULL; + bool arg0_neg = false; + bool isAbs = true; + tree variable; + + + /* One of the alternatives must come from a block ending with + a COND_EXPR. The other block must be only a statement with + an assignment of a variable of -arg0 or -arg1. */ + last0 = last_stmt (bb->pred->src); + last1 = last_stmt (bb->pred->pred_next->src); + + if (last0 && TREE_CODE (last0) == COND_EXPR) + { + cond_block = bb->pred->src; + other_block = bb->pred->pred_next->src; + } + if (last0 && TREE_CODE (last0) == COND_EXPR) + { + cond_block = bb->pred->src; + other_block = bb->pred->pred_next->src; + } + else if (last1 && TREE_CODE (last1) == COND_EXPR) + { + other_block = bb->pred->src; + cond_block = bb->pred->pred_next->src; + } + else + return false; + + /* COND_BLOCK must have precisely two successors. We indirectly + verify that those successors are BB and OTHER_BLOCK. */ + if (!cond_block->succ + || !cond_block->succ->succ_next + || cond_block->succ->succ_next->succ_next + || (cond_block->succ->flags & EDGE_ABNORMAL) != 0 + || (cond_block->succ->succ_next->flags & EDGE_ABNORMAL) != 0) + return false; + + /* OTHER_BLOCK must have a single predecessor which is COND_BLOCK, + OTHER_BLOCK must have a single successor which is BB and + OTHER_BLOCK must have no PHI nodes. */ + if (!other_block->pred + || other_block->pred->src != cond_block + || other_block->pred->pred_next + || !other_block->succ + || other_block->succ->dest != bb + || other_block->succ->succ_next + || phi_nodes (other_block)) + return false; + + /* OTHER_BLOCK must have one executable statement, the assignment. */ + bsi = bsi_start (other_block); + while (!bsi_end_p (bsi)) + { + tree stmt = bsi_stmt (bsi); + if (TREE_CODE (stmt) == LABEL_EXPR + || IS_EMPTY_STMT (stmt)) + { + bsi_next (&bsi); + continue; + } + /* Is this the assignment */ + if (TREE_CODE (stmt) == MODIFY_EXPR) + { + tree stmt_arg0 = TREE_OPERAND (stmt, 0); + tree stmt_arg1 = TREE_OPERAND (stmt, 1); + if (TREE_CODE (stmt_arg1) == NEGATE_EXPR) + { + stmt_arg1 = TREE_OPERAND (stmt_arg1, 0); + /* The assignment has to be arg0 = arg1 or arg1 = arg0. */ + /* FIXME: Handle more complex cases like arg1 = a-b and before + the conditional arg0 = b-a; */ + if (stmt_arg0 == arg0 && stmt_arg1 == arg1) + { + asign = stmt; + arg0_neg = false; + break; + } + if (stmt_arg0 == arg1 && stmt_arg1 == arg0) + { + asign = stmt; + arg0_neg = true; + break; + } + } + } + return false; + } + + /* We did not find an assignment so we cannot do the replacement. */ + if (asign == NULL) + return false; + + + /* The rest of the OTHER_BLOCK should be empty. */ + bsi_next (&bsi); + while (!bsi_end_p (bsi) + && (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR + || IS_EMPTY_STMT (bsi_stmt (bsi)))) + bsi_next (&bsi); + + /* There was some other expression in the basic block + so this optimization cannot be done. */ + if (!bsi_end_p (bsi)) + return false; + + cond = COND_EXPR_COND (last_stmt (cond_block)); + result = PHI_RESULT (phi); + + /* We need to know which is the true edge and which is the false + edge so that we know if have abs or negative abs. */ + extract_true_false_edges_from_block (cond_block, &true_edge, &false_edge); + + /* Only less than, greater than, and those with "and equal" to them + are the ones which are needed for abs/nabs. */ + switch (TREE_CODE (cond)) + { + case LT_EXPR: + case LE_EXPR: + { + if (arg0_neg) + { + /* FIXME: Handle all these cases. */ + if (PHI_ARG_EDGE (phi, 0) == true_edge) + return false; + + /* This is the case where arg0 is the variable + which is negatived and is the variable on + the false edge so it can be converted into + an nabs. */ + else if (PHI_ARG_EDGE (phi, 0) == false_edge) + { + isAbs = true; + } + else if (PHI_ARG_EDGE (phi, 1) == false_edge) + return false; + else if (PHI_ARG_EDGE (phi, 1) == true_edge) + return false; + } + else + { + /* FIXME: Handle all these cases. */ + if (PHI_ARG_EDGE (phi, 0) == true_edge) + return false; + else if (PHI_ARG_EDGE (phi, 0) == false_edge) + return false; + else if (PHI_ARG_EDGE (phi, 1) == false_edge) + return false; + + /* This is the case where arg1 is the variable + which is negatived and is the variable on + the true edge so it can be converted into + an nabs. */ + else if (PHI_ARG_EDGE (phi, 1) == true_edge) + { + isAbs = false; + } + } + break; + } + case GT_EXPR: + case GE_EXPR: + { + if (arg0_neg) + { + /* FIXME: Handle all these cases. */ + if (PHI_ARG_EDGE (phi, 0) == true_edge) + return false; + + /* This is the case where arg0 is the variable + which is negatived and is the variable on + the false edge so it can be converted into + an nabs. */ + else if (PHI_ARG_EDGE (phi, 0) == false_edge) + { + isAbs = false; + } + else if (PHI_ARG_EDGE (phi, 1) == false_edge) + return false; + else if (PHI_ARG_EDGE (phi, 1) == true_edge) + return false; + } + else + { + /* FIXME: Handle all these cases. */ + if (PHI_ARG_EDGE (phi, 0) == true_edge) + return false; + else if (PHI_ARG_EDGE (phi, 0) == false_edge) + return false; + else if (PHI_ARG_EDGE (phi, 1) == false_edge) + return false; + + /* This is the case where arg1 is the variable + which is negatived and is the variable on + the true edge so it can be converted into + an abs. */ + else if (PHI_ARG_EDGE (phi, 1) == true_edge) + { + isAbs = true; + } + } + break; + } + default: + return false; + } + + + /* Make sure the conditional is arg[01] OP y. */ + + if (TREE_OPERAND (cond, 0) != (arg0_neg ? arg0 : arg1)) + return false; + + /* If the type says honor signed zeros we cannot do this + optimization. */ + if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1)))) + return false; + + /* Make sure that the arg[01] is comparing against 0. */ + if (FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (cond, 1))) + ? real_zerop (TREE_OPERAND (cond, 1)) + : integer_zerop (TREE_OPERAND (cond, 1))) + ; + else + return false; + + + + result = PHI_RESULT (phi); + /* Make a new variable to hold the abs if need be. */ + if (!isAbs) + variable = make_temp (TREE_TYPE (result)); + else + variable = result; + + + /* Build the modify expression with abs expression. */ + new = build (MODIFY_EXPR, TREE_TYPE (variable), + variable, build1 (ABS_EXPR, TREE_TYPE (variable), + arg0_neg ? arg0 : arg1)); + + /* Insert our new statement at the head of our block. */ + bsi = bsi_start (bb); + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + + if (!isAbs) + { + new = build (MODIFY_EXPR, TREE_TYPE (result), + result, build1 (NEGATE_EXPR, TREE_TYPE (variable), + variable)); + + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + } + + /* Register our new statement as the defining statement for + the result. */ + SSA_NAME_DEF_STMT (result) = new; + + /* Remove the now useless PHI node. + + We do not want to use remove_phi_node since that releases the + SSA_NAME as well and the SSA_NAME is still being used. */ + release_phi_node (phi); + bb_ann (bb)->phi_nodes = NULL; + + + /* Disconnect the edge leading into the empty block. That will + make the empty block unreachable and it will be removed later. */ + if (cond_block->succ->dest == bb) + { + cond_block->succ->flags |= EDGE_FALLTHRU; + cond_block->succ->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + ssa_remove_edge (cond_block->succ->succ_next); + } + else + { + cond_block->succ->succ_next->flags |= EDGE_FALLTHRU; + cond_block->succ->succ_next->flags + &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + ssa_remove_edge (cond_block->succ); + } + + /* Eliminate the COND_EXPR at the end of COND_BLOCK. */ + bsi = bsi_last (cond_block); + bsi_remove (&bsi); + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "COND_EXPR in block %d and PHI in block %d converted to straightline code (using ABS).\n", + cond_block->index, + bb->index); + + /* Note that we optimized this PHI. */ + return true; +} + +/* The function value_replacement does the main work of doing the value + replacement. Return true if the replacement is done. Otherwise return false. + bb is the basic block where the replacement is going to be done on. arg0 + is argument 0 from the phi. Likewise for arg1. */ + +static bool +value_replacement (basic_block bb, tree phi, tree arg0, tree arg1) +{ + tree result; + basic_block other_block = NULL; + basic_block cond_block = NULL; + tree last0, last1, new, cond; + block_stmt_iterator bsi; + edge true_edge, false_edge; + bool use_arg0; + + + /* One of the alternatives must come from a block ending with + a COND_EXPR. The other block must be entirely empty, except + for labels. */ + last0 = last_stmt (bb->pred->src); + last1 = last_stmt (bb->pred->pred_next->src); + if (last0 && TREE_CODE (last0) == COND_EXPR) + { + cond_block = bb->pred->src; + other_block = bb->pred->pred_next->src; + } + else if (last1 && TREE_CODE (last1) == COND_EXPR) + { + other_block = bb->pred->src; + cond_block = bb->pred->pred_next->src; + } + else + return false; + + /* COND_BLOCK must have precisely two successors. We indirectly + verify that those successors are BB and OTHER_BLOCK. */ + if (!cond_block->succ + || !cond_block->succ->succ_next + || cond_block->succ->succ_next->succ_next + || (cond_block->succ->flags & EDGE_ABNORMAL) != 0 + || (cond_block->succ->succ_next->flags & EDGE_ABNORMAL) != 0) + return false; + + + /* OTHER_BLOCK must have a single predecessor which is COND_BLOCK, + OTHER_BLOCK must have a single successor which is BB and + OTHER_BLOCK must have no PHI nodes. */ + if (!other_block->pred + || other_block->pred->src != cond_block + || other_block->pred->pred_next + || !other_block->succ + || other_block->succ->dest != bb + || other_block->succ->succ_next + || phi_nodes (other_block)) + return false; + + /* OTHER_BLOCK must have no executable statements. */ + bsi = bsi_start (other_block); + while (!bsi_end_p (bsi) + && (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR + || IS_EMPTY_STMT (bsi_stmt (bsi)))) + bsi_next (&bsi); + + if (!bsi_end_p (bsi)) + return false; + + cond = COND_EXPR_COND (last_stmt (cond_block)); + result = PHI_RESULT (phi); + + /* We need to know which is the true edge and which is the false + edge so that we know if have abs or negative abs. */ + extract_true_false_edges_from_block (cond_block, &true_edge, &false_edge); + + /* For this optimization to happen, the condition has to be + either equal or not equal. */ + switch (TREE_CODE (cond)) + { + case EQ_EXPR: + /* TODO: handle this case. */ + /* This one is not that important as it is already handled by + DOM. */ + return false; + + case NE_EXPR: + /* FIXME: Handle all these cases. */ + if (PHI_ARG_EDGE (phi, 0) == true_edge) + return false; + else if (PHI_ARG_EDGE (phi, 0) == false_edge) + { + use_arg0 = false; + } + else if (PHI_ARG_EDGE (phi, 1) == false_edge) + return false; + else if (PHI_ARG_EDGE (phi, 1) == true_edge) + return false; + + break; + + default: + return false; + } + + if (operand_equal_p (TREE_OPERAND (cond, 0), arg0, 0) + && operand_equal_p (TREE_OPERAND (cond, 1), arg1, 0)) + { + return false; + /* TODO: handle this case. */ + } + else if (operand_equal_p (TREE_OPERAND (cond, 0), arg1, 0) + && operand_equal_p (TREE_OPERAND (cond, 1), arg0, 0)) + { + /* TODO: handle this case. */ + if (use_arg0) + return false; + } + else + return false; + + /* If the type says honor signed zeros we cannot do this + optimization. */ + if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1)))) + return false; + + result = PHI_RESULT (phi); + /* Build the modify expression with abs expression. */ + new = build (MODIFY_EXPR, TREE_TYPE (result), + result, use_arg0 ? arg0 : arg1); + + /* Insert our new statement at the head of our block. */ + bsi = bsi_start (bb); + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + + /* Register our new statement as the defining statement for + the result. */ + SSA_NAME_DEF_STMT (PHI_RESULT (phi)) = new; + + /* Remove the now useless PHI node. + + We do not want to use remove_phi_node since that releases the + SSA_NAME as well and the SSA_NAME is still being used. */ + release_phi_node (phi); + bb_ann (bb)->phi_nodes = NULL; + + + /* Eliminate the COND_EXPR at the end of COND_BLOCK. */ + bsi = bsi_last (cond_block); + bsi_remove (&bsi); + + + /* Disconnect the edge leading into the empty block. That will + make the empty block unreachable and it will be removed later. */ + if (cond_block->succ->dest == bb) + { + cond_block->succ->flags |= EDGE_FALLTHRU; + cond_block->succ->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + ssa_remove_edge (cond_block->succ->succ_next); + } + else + { + cond_block->succ->succ_next->flags |= EDGE_FALLTHRU; + cond_block->succ->succ_next->flags + &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + ssa_remove_edge (cond_block->succ); + } + + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n", + cond_block->index, + bb->index); + + /* Note that we optimized this PHI. */ + return true; + +} + + /* Always do these optimizations if we have SSA trees to work on. */ static bool @@ -296,7 +900,8 @@ struct tree_opt_pass pass_phiopt = 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */ - | TODO_verify_ssa + | TODO_verify_ssa | TODO_rename_vars + | TODO_verify_flow }; |