[PATCH] Improve uninit_analysis::collect_phi_def_edges

[Richard Biener via Gcc-patches]

This avoids expanding an edge to those of a PHI def if it is not
may-undefined, reducing the number of compute_control_dep_chain calls.

Bootstrap and regtest in progress on x86_64-unknown-linux-gnu.

        * gimple-predicate-analysis.cc
        (uninit_analysis::collect_phi_def_edges): Only expand a
        PHI def edge when it is possibly undefined.
---
 gcc/gimple-predicate-analysis.cc | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/gcc/gimple-predicate-analysis.cc b/gcc/gimple-predicate-analysis.cc
index 079e06009fd..0d973a9e25a 100644
--- a/gcc/gimple-predicate-analysis.cc
+++ b/gcc/gimple-predicate-analysis.cc
@@ -605,11 +605,7 @@ uninit_analysis::collect_phi_def_edges (gphi *phi, 
basic_block cd_root,
        {
          gimple *def = SSA_NAME_DEF_STMT (opnd);
 
-         if (gimple_code (def) == GIMPLE_PHI
-             && dominated_by_p (CDI_DOMINATORS, gimple_bb (def), cd_root))
-           collect_phi_def_edges (as_a<gphi *> (def), cd_root, edges,
-                                  visited);
-         else if (!m_eval (opnd))
+         if (!m_eval (opnd))
            {
              if (dump_file && (dump_flags & TDF_DETAILS))
                {
@@ -622,6 +618,10 @@ uninit_analysis::collect_phi_def_edges (gphi *phi, 
basic_block cd_root,
                }
              edges->safe_push (opnd_edge);
            }
+         else if (gimple_code (def) == GIMPLE_PHI
+                  && dominated_by_p (CDI_DOMINATORS, gimple_bb (def), cd_root))
+           collect_phi_def_edges (as_a<gphi *> (def), cd_root, edges,
+                                  visited);
        }
       else
        {
-- 
2.35.3