diff options
Diffstat (limited to 'gcc/tree-ssa-threadbackward.c')
| -rw-r--r-- | gcc/tree-ssa-threadbackward.c | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c index 449232c..e729923 100644 --- a/gcc/tree-ssa-threadbackward.c +++ b/gcc/tree-ssa-threadbackward.c @@ -43,6 +43,7 @@ along with GCC; see the file COPYING3. If not see #include "ssa.h" #include "tree-cfgcleanup.h" #include "tree-pretty-print.h" +#include "cfghooks.h" // Path registry for the backwards threader. After all paths have been // registered with register_path(), thread_through_all_blocks() is called @@ -564,7 +565,10 @@ back_threader_registry::thread_through_all_blocks (bool may_peel_loop_headers) TAKEN_EDGE, otherwise it is NULL. CREATES_IRREDUCIBLE_LOOP, if non-null is set to TRUE if threading this path - would create an irreducible loop. */ + would create an irreducible loop. + + ?? It seems we should be able to loosen some of the restrictions in + this function after loop optimizations have run. */ bool back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path, @@ -725,7 +729,11 @@ back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path, the last entry in the array when determining if we thread through the loop latch. */ if (loop->latch == bb) - threaded_through_latch = true; + { + threaded_through_latch = true; + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " (latch)"); + } } gimple *stmt = get_gimple_control_stmt (m_path[0]); @@ -845,6 +853,22 @@ back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path, "a multiway branch.\n"); return false; } + + /* Threading through an empty latch would cause code to be added to + the latch. This could alter the loop form sufficiently to cause + loop optimizations to fail. Disable these threads until after + loop optimizations have run. */ + if ((threaded_through_latch + || (taken_edge && taken_edge->dest == loop->latch)) + && !(cfun->curr_properties & PROP_loop_opts_done) + && empty_block_p (loop->latch)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + " FAIL: FSM Thread through latch before loop opts would create non-empty latch\n"); + return false; + + } return true; } |