diff options
Diffstat (limited to 'gcc/tree-ssa-loop-ch.c')
| -rw-r--r-- | gcc/tree-ssa-loop-ch.c | 38 |
1 files changed, 35 insertions, 3 deletions
diff --git a/gcc/tree-ssa-loop-ch.c b/gcc/tree-ssa-loop-ch.c index 33e85c839dc..3385029b3bf 100644 --- a/gcc/tree-ssa-loop-ch.c +++ b/gcc/tree-ssa-loop-ch.c @@ -132,7 +132,7 @@ copy_loop_headers (void) loop_iterator li; struct loop *loop; basic_block header; - edge exit, entry; + edge exit, new_exit, entry; basic_block *bbs, *copied_bbs; unsigned n_bbs; unsigned bbs_size; @@ -180,9 +180,41 @@ copy_loop_headers (void) /* Find a successor of header that is inside a loop; i.e. the new header after the condition is copied. */ if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)) - exit = EDGE_SUCC (header, 0); + new_exit = EDGE_SUCC (header, 0); else - exit = EDGE_SUCC (header, 1); + new_exit = EDGE_SUCC (header, 1); + /* If we already have copied a header that tests a variable, + and all that we'd have left is an in/decrement of that variable, + that variable is most likely the biv, and the 'header' we are + currently looking at is the actual loop body. This happens + for instance with libgcc2.c:__gcc_bcmp . */ + if (header != loop->header + && single_succ_p (new_exit->dest) + && EDGE_SUCC (new_exit->dest, 0)->dest == loop->header) + { + gimple cond = last_and_only_stmt (loop->header); + gimple modify = last_stmt (new_exit->dest); + + if (cond && modify && gimple_code (modify) == GIMPLE_ASSIGN + && modify == gsi_stmt (gsi_after_labels (new_exit->dest))) + { + /* We checked earlier that cond is a GIMPLE_COND. */ + tree var; + tree m_var = gimple_get_lhs (modify); + + if (truth_value_p (gimple_cond_code (cond))) + var = gimple_cond_lhs (cond); + else + /* If variable is used as dircetly condition, use that. */ + /* Abort so that we can use gdb to inspect this point live. */ + gcc_unreachable (); + if (TREE_CODE (var) == SSA_NAME + && TREE_CODE (m_var) == SSA_NAME + && SSA_NAME_VAR (var) == SSA_NAME_VAR (m_var)) + break; + } + } + exit = new_exit; bbs[n_bbs++] = header; gcc_assert (bbs_size > n_bbs); header = exit->dest; |