[gcc r14-203] PHIOPT: Ignore predicates for match-and-simplify phi-opt

[gcc r14-203] PHIOPT: Ignore predicates for match-and-simplify phi-opt

[Andrew Pinski]

https://gcc.gnu.org/g:a2339e0fe9dbefdeca49a8105c7a547231c02d34

commit r14-203-ga2339e0fe9dbefdeca49a8105c7a547231c02d34
Author: Andrew Pinski <apinski@marvell.com>
Date:   Sun Apr 9 22:47:50 2023 +0000

    PHIOPT: Ignore predicates for match-and-simplify phi-opt
    
    This fixes a missed optimization where early phi-opt would
    not work when there was predicates. The easiest fix is
    to change empty_bb_or_one_feeding_into_p to ignore those
    statements while checking for only feeding statement.
    
    Note phi-opt-23.c and phi-opt-24.c still fail as we don't handle
    diamond form in match_and_simplify phiopt yet.
    
    OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
    
    gcc/ChangeLog:
    
            * tree-ssa-phiopt.cc (empty_bb_or_one_feeding_into_p):
            Instead of calling last_and_only_stmt, look for the last statement
            manually.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/tree-ssa/ssa-ifcombine-13.c: Add -fno-ssa-phiopt.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-13.c |  4 +++-
 gcc/tree-ssa-phiopt.cc                           | 22 ++++++++++++++++++++--
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-13.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-13.c
index 425eb3d6481..7976544c79b 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-13.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-13.c
@@ -1,5 +1,7 @@
 /* { dg-do compile } */
-/* { dg-options "-O1 -fdump-tree-optimized-details-blocks --param logical-op-non-short-circuit=1" } */
+/* Disable phi-opt as it is no longer confused by predicate which had allowed ifcombine to work in the past.
+   Note this testcase is about ifcombine rather than phi-opt. */
+/* { dg-options "-O1 -fdump-tree-optimized-details-blocks --param logical-op-non-short-circuit=1 -fno-ssa-phiopt" } */
 
 _Bool f1(_Bool a, _Bool b)
 {
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index f3164b8511b..f17c3507d11 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -960,9 +960,27 @@ empty_bb_or_one_feeding_into_p (basic_block bb,
   if (!gimple_seq_empty_p (phi_nodes (bb)))
     return false;
 
-  stmt_to_move = last_and_only_stmt (bb);
+  gimple_stmt_iterator gsi;
+
+  gsi = gsi_start_nondebug_after_labels_bb (bb);
+  while (!gsi_end_p (gsi))
+    {
+      gimple *s = gsi_stmt (gsi);
+      gsi_next_nondebug (&gsi);
+      /* Skip over Predict and nop statements. */
+      if (gimple_code (s) == GIMPLE_PREDICT
+	  || gimple_code (s) == GIMPLE_NOP)
+	continue;
+      /* If there is more one statement return false. */
+      if (stmt_to_move)
+	return false;
+      stmt_to_move = s;
+    }
+
+  /* The only statement here was a Predict or a nop statement
+     so return true. */
   if (!stmt_to_move)
-    return false;
+    return true;
 
   if (gimple_vuse (stmt_to_move))
     return false;