diff options
Diffstat (limited to 'gcc/tree-ssa-threadbackward.c')
| -rw-r--r-- | gcc/tree-ssa-threadbackward.c | 54 |
1 files changed, 36 insertions, 18 deletions
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c index 55dbcad..3028504 100644 --- a/gcc/tree-ssa-threadbackward.c +++ b/gcc/tree-ssa-threadbackward.c @@ -286,6 +286,37 @@ fsm_find_control_statement_thread_paths (tree name, break; } + /* PHIs in the path will create degenerate PHIS in the + copied path which will then get propagated away, so + looking at just the duplicate path the PHIs would + seem unimportant. + + But those PHIs, because they're assignments to objects + typically with lives that exist outside the thread path, + will tend to generate PHIs (or at least new PHI arguments) + at points where we leave the thread path and rejoin + the original blocks. So we do want to account for them. + + We ignore virtual PHIs. We also ignore cases where BB + has a single incoming edge. That's the most common + degenerate PHI we'll see here. Finally we ignore PHIs + that are associated with the value we're tracking as + that object likely dies. */ + if (EDGE_COUNT (bb->succs) > 1 && EDGE_COUNT (bb->preds) > 1) + { + for (gphi_iterator gsip = gsi_start_phis (bb); + !gsi_end_p (gsip); + gsi_next (&gsip)) + { + gphi *phi = gsip.phi (); + tree dst = gimple_phi_result (phi); + + if (SSA_NAME_VAR (dst) != SSA_NAME_VAR (name) + && !virtual_operand_p (dst)) + ++n_insns; + } + } + for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next_nondebug (&gsi)) @@ -324,6 +355,11 @@ fsm_find_control_statement_thread_paths (tree name, threaded_through_latch = true; } + /* We are going to remove the control statement at the end of the + last block in the threading path. So don't count it against our + statement count. */ + n_insns--; + gimple *stmt = get_gimple_control_stmt ((*path)[0]); gcc_assert (stmt); /* We have found a constant value for ARG. For GIMPLE_SWITCH @@ -352,24 +388,6 @@ fsm_find_control_statement_thread_paths (tree name, == DOMST_NONDOMINATING)) creates_irreducible_loop = true; - /* PHIs in the final target and only the final target will need - to be duplicated. So only count those against the number - of statements. */ - gphi_iterator gsip; - for (gsip = gsi_start_phis (taken_edge->dest); - !gsi_end_p (gsip); - gsi_next (&gsip)) - { - gphi *phi = gsip.phi (); - tree dst = gimple_phi_result (phi); - - /* We consider any non-virtual PHI as a statement since it - count result in a constant assignment or copy - operation. */ - if (!virtual_operand_p (dst)) - ++n_insns; - } - if (path_crosses_loops) { if (dump_file && (dump_flags & TDF_DETAILS)) |