From 1833df5cfe2cf85a9cf1de054ab53569f59e0ae5 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Tue, 18 May 2004 10:23:25 -0600 Subject: [PATCH] tree-ssa-phiopt.c (replace_phi_with_stmt): New function extracted from conditional_replacement. * tree-ssa-phiopt.c (replace_phi_with_stmt): New function extracted from conditional_replacement. (candidate_bb_for_phi_optimization): Similarly. (conditional_replacement): Use replace_phi_with_stmt and candidate_bb_for_phi_optimization. From-SVN: r81996 --- gcc/ChangeLog | 6 ++ gcc/tree-ssa-phiopt.c | 167 +++++++++++++++++++++++++++--------------- 2 files changed, 113 insertions(+), 60 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c7340043c0b..a294e940cfe 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,11 @@ 2004-05-18 Jeff Law + * tree-ssa-phiopt.c (replace_phi_with_stmt): New function extracted + from conditional_replacement. + (candidate_bb_for_phi_optimization): Similarly. + (conditional_replacement): Use replace_phi_with_stmt and + candidate_bb_for_phi_optimization. + * tree-ssa-phiopt.c: Fix various formatting issues. 2004-05-18 Steven Bosscher diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c index 85dceee42cb..a29b8f71a94 100644 --- a/gcc/tree-ssa-phiopt.c +++ b/gcc/tree-ssa-phiopt.c @@ -38,6 +38,12 @@ 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 void replace_phi_with_stmt (block_stmt_iterator, basic_block, + basic_block, tree, tree); +static bool candidate_bb_for_phi_optimization (basic_block, + basic_block *, + basic_block *); + /* This pass eliminates PHI nodes which can be trivially implemented as an assignment from a conditional expression. ie if we have something @@ -97,32 +103,26 @@ tree_ssa_phiopt (void) cleanup_tree_cfg (); } -/* The function conditional_replacement does the main work of doing the - conditional 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 PHI. Likewise for ARG1. */ +/* BB is a basic block which has only one PHI node with precisely two + arguments. + + Examine both of BB's predecessors to see if one ends with a + COND_EXPR and the other is an empty block. If so, then we may + be able to optimize PHI nodes at the start of BB. + + If so, mark store the block with the COND_EXPR into COND_BLOCK_P + and the other block into OTHER_BLOCK_P and return true, otherwise + return false. */ static bool -conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) +candidate_bb_for_phi_optimization (basic_block bb, + basic_block *cond_block_p, + basic_block *other_block_p) { - tree result; - tree old_result = NULL; - basic_block other_block = NULL; - basic_block cond_block = NULL; - tree last0, last1, new, cond; + tree last0, last1; block_stmt_iterator bsi; - edge true_edge, false_edge; - tree new_var = NULL; + basic_block cond_block, other_block; - /* The PHI arguments have the constants 0 and 1, then convert - it to the conditional. */ - if ((integer_zerop (arg0) && integer_onep (arg1)) - || (integer_zerop (arg1) && integer_onep (arg0))) - ; - else - return false; - /* One of the alternatives must come from a block ending with a COND_EXPR. The other block must be entirely empty, except for labels. */ @@ -171,7 +171,91 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) if (!bsi_end_p (bsi)) return false; + + *cond_block_p = cond_block; + *other_block_p = other_block; + /* Everything looks OK. */ + return true; +} + +/* Replace PHI in block BB with statement NEW. NEW is inserted after + BSI. Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK + is known to have two edges, one of which must reach BB). */ + +static void +replace_phi_with_stmt (block_stmt_iterator bsi, basic_block bb, + basic_block cond_block, tree phi, tree new) +{ + /* Insert our new statement at the head of our block. */ + 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; + + /* 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.\n", + cond_block->index, + bb->index); +} + +/* The function conditional_replacement does the main work of doing the + conditional 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 PHI. Likewise for ARG1. */ + +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 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. */ + if ((integer_zerop (arg0) && integer_onep (arg1)) + || (integer_zerop (arg1) && integer_onep (arg0))) + ; + else + return false; + if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block)) + return false; + /* If the condition is not a naked SSA_NAME and its type does not match the type of the result, then we have to create a new variable to optimize this case as it would likely create @@ -270,45 +354,8 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1) PHI_RESULT (phi), cond); } - 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; - - /* 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.\n", - cond_block->index, - bb->index); - + replace_phi_with_stmt (bsi, bb, cond_block, phi, new); + /* Note that we optimized this PHI. */ return true; } -- 2.30.2