diff options
Diffstat (limited to 'gcc/tree-ssa-threadedge.c')
-rw-r--r-- | gcc/tree-ssa-threadedge.c | 70 |
1 files changed, 67 insertions, 3 deletions
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c index c3ea2d6..785227d 100644 --- a/gcc/tree-ssa-threadedge.c +++ b/gcc/tree-ssa-threadedge.c @@ -1157,6 +1157,68 @@ thread_through_normal_block (edge e, return 0; } +/* There are basic blocks look like: + <P0> + p0 = a CMP b ; or p0 = (INT) (a CMP b) + goto <X>; + + <P1> + p1 = c CMP d + goto <X>; + + <X> + # phi = PHI <p0 (P0), p1 (P1)> + if (phi != 0) goto <Y>; else goto <Z>; + + Then, edge (P0,X) or (P1,X) could be marked as EDGE_START_JUMP_THREAD + And edge (X,Y), (X,Z) is EDGE_COPY_SRC_JOINER_BLOCK + + Return true if E is (P0,X) or (P1,X) */ + +bool +edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (edge e) +{ + /* See if there is only one stmt which is gcond. */ + gcond *gs; + if (!(gs = safe_dyn_cast<gcond *> (last_and_only_stmt (e->dest)))) + return false; + + /* See if gcond's cond is "(phi !=/== 0/1)" in the basic block. */ + tree cond = gimple_cond_lhs (gs); + enum tree_code code = gimple_cond_code (gs); + tree rhs = gimple_cond_rhs (gs); + if (TREE_CODE (cond) != SSA_NAME + || (code != NE_EXPR && code != EQ_EXPR) + || (!integer_onep (rhs) && !integer_zerop (rhs))) + return false; + gphi *phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (cond)); + if (phi == NULL || gimple_bb (phi) != e->dest) + return false; + + /* Check if phi's incoming value is CMP. */ + gassign *def; + tree value = PHI_ARG_DEF_FROM_EDGE (phi, e); + if (TREE_CODE (value) != SSA_NAME + || !has_single_use (value) + || !(def = dyn_cast <gassign *> (SSA_NAME_DEF_STMT (value)))) + return false; + + /* Or if it is (INT) (a CMP b). */ + if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def))) + { + value = gimple_assign_rhs1 (def); + if (TREE_CODE (value) != SSA_NAME + || !has_single_use (value) + || !(def = dyn_cast<gassign *> (SSA_NAME_DEF_STMT (value)))) + return false; + } + + if (TREE_CODE_CLASS (gimple_assign_rhs_code (def)) != tcc_comparison) + return false; + + return true; +} + /* We are exiting E->src, see if E->dest ends with a conditional jump which has a known value when reached via E. @@ -1317,10 +1379,12 @@ thread_across_edge (gcond *dummy_cond, /* If we were able to thread through a successor of E->dest, then record the jump threading opportunity. */ - if (found) + if (found + || edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (e)) { - propagate_threaded_block_debug_into (path->last ()->e->dest, - taken_edge->dest); + if (taken_edge->dest != path->last ()->e->dest) + propagate_threaded_block_debug_into (path->last ()->e->dest, + taken_edge->dest); register_jump_thread (path); } else |