diff options
Diffstat (limited to 'gcc/tree-ssa-threadedge.c')
| -rw-r--r-- | gcc/tree-ssa-threadedge.c | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c index bd78c6b..b8d4b13 100644 --- a/gcc/tree-ssa-threadedge.c +++ b/gcc/tree-ssa-threadedge.c @@ -231,15 +231,6 @@ record_temporary_equivalences_from_stmts_at_dest (edge e, if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR) continue; - /* Safely handle threading across loop backedges. Only allowing - a conditional at the target of the backedge is over conservative, - but still allows us to capture the majority of the cases where - we can thread across a loop backedge. */ - if ((e->flags & EDGE_DFS_BACK) != 0 - && TREE_CODE (stmt) != COND_EXPR - && TREE_CODE (stmt) != SWITCH_EXPR) - return NULL; - /* If the statement has volatile operands, then we assume we can not thread through this block. This is overly conservative in some ways. */ @@ -496,6 +487,27 @@ thread_across_edge (tree dummy_cond, { tree stmt; + /* If E is a backedge, then we want to verify that the COND_EXPR, + SWITCH_EXPR or GOTO_EXPR at the end of e->dest is not affected + by any statements in e->dest. If it is affected, then it is not + safe to thread this edge. */ + if (e->flags & EDGE_DFS_BACK) + { + ssa_op_iter iter; + use_operand_p use_p; + tree last = bsi_stmt (bsi_last (e->dest)); + + FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE) + { + tree use = USE_FROM_PTR (use_p); + + if (TREE_CODE (use) == SSA_NAME + && TREE_CODE (SSA_NAME_DEF_STMT (use)) != PHI_NODE + && bb_for_stmt (SSA_NAME_DEF_STMT (use)) == e->dest) + goto fail; + } + } + stmt_count = 0; /* PHIs create temporary equivalences. */ |