diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-101.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-101.c new file mode 100644 index 0000000000000000000000000000000000000000..c67f211dcf6306dc24eed2a8e79e53a0f10118e7 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-101.c @@ -0,0 +1,47 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-fre1-details" } */ + +int test1 (int i, int j) +{ + int k; + if (i != j) + k = i; + else + k = j; + return k; +} + +int test2 (int i, int j) +{ + int k; + if (i != j) + k = j; + else + k = i; + return k; +} + +int test3 (int i, int j) +{ + int k; + if (i == j) + k = j; + else + k = i; + return k; +} + +int test4 (int i, int j) +{ + int k; + if (i == j) + k = i; + else + k = j; + return k; +} + +/* We'd expect 4 hits but since we only keep one forwarder the + VN predication machinery cannot record something for the entry + block since it doesn't work on edges but on their source. */ +/* { dg-final { scan-tree-dump-times "equal on edge" 2 "fre1" } } */ diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc index 37484403c5667bee7277267162fec9a0caac2ed7..1e7763baa38e9891f70cb883fddc9488dcb40ea6 100644 --- a/gcc/tree-ssa-sccvn.cc +++ b/gcc/tree-ssa-sccvn.cc @@ -5793,7 +5793,8 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p) /* See if all non-TOP arguments have the same value. TOP is equivalent to everything, so we can ignore it. */ - FOR_EACH_EDGE (e, ei, gimple_bb (phi)->preds) + basic_block bb = gimple_bb (phi); + FOR_EACH_EDGE (e, ei, bb->preds) if (e->flags & EDGE_EXECUTABLE) { tree def = PHI_ARG_DEF_FROM_EDGE (phi, e); @@ -5838,6 +5839,54 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p) && known_eq (soff, doff)) continue; } + /* There's also the possibility to use equivalences. */ + if (!FLOAT_TYPE_P (TREE_TYPE (def))) + { + vn_nary_op_t vnresult; + tree ops[2]; + ops[0] = def; + ops[1] = sameval; + tree val = vn_nary_op_lookup_pieces (2, EQ_EXPR, + boolean_type_node, + ops, &vnresult); + if (! val && vnresult && vnresult->predicated_values) + { + val = vn_nary_op_get_predicated_value (vnresult, e->src); + if (val && integer_truep (val)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Predication says "); + print_generic_expr (dump_file, def, TDF_NONE); + fprintf (dump_file, " and "); + print_generic_expr (dump_file, sameval, TDF_NONE); + fprintf (dump_file, " are equal on edge %d -> %d\n", + e->src->index, e->dest->index); + } + continue; + } + /* If on all previous edges the value was equal to def + we can change sameval to def. */ + if (EDGE_COUNT (bb->preds) == 2 + && (val = vn_nary_op_get_predicated_value + (vnresult, EDGE_PRED (bb, 0)->src)) + && integer_truep (val)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Predication says "); + print_generic_expr (dump_file, def, TDF_NONE); + fprintf (dump_file, " and "); + print_generic_expr (dump_file, sameval, TDF_NONE); + fprintf (dump_file, " are equal on edge %d -> %d\n", + EDGE_PRED (bb, 0)->src->index, + EDGE_PRED (bb, 0)->dest->index); + } + sameval = def; + continue; + } + } + } sameval = NULL_TREE; break; }