diff options
Diffstat (limited to 'gcc/tree-ssa-pre.c')
| -rw-r--r-- | gcc/tree-ssa-pre.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c index ff59d53..c6aa587 100644 --- a/gcc/tree-ssa-pre.c +++ b/gcc/tree-ssa-pre.c @@ -1468,10 +1468,20 @@ phi_translate_1 (pre_expr expr, bitmap_set_t set1, bitmap_set_t set2, leader for it. */ if (constant->kind != CONSTANT) { - unsigned value_id = get_expr_value_id (constant); - constant = find_leader_in_sets (value_id, set1, set2); - if (constant) - return constant; + /* Do not allow simplifications to non-constants over + backedges as this will likely result in a loop PHI node + to be inserted and increased register pressure. + See PR77498 - this avoids doing predcoms work in + a less efficient way. */ + if (find_edge (pred, phiblock)->flags & EDGE_DFS_BACK) + ; + else + { + unsigned value_id = get_expr_value_id (constant); + constant = find_leader_in_sets (value_id, set1, set2); + if (constant) + return constant; + } } else return constant; |