[gcc r13-2525] sched1: Fix -fcompare-debug issue in schedule_region [PR105586]

[Surya Kumari Jangala <jskumari@gcc.gnu.org>]

https://gcc.gnu.org/g:bec35caafae8db0278e1d037a7ba00c3e6899bbd

commit r13-2525-gbec35caafae8db0278e1d037a7ba00c3e6899bbd
Author: Surya Kumari Jangala <jskumari@linux.ibm.com>
Date:   Tue Aug 2 23:00:03 2022 -0500

    sched1: Fix -fcompare-debug issue in schedule_region [PR105586]
    
    In schedule_region(), a basic block that does not contain any real insns
    is not scheduled and the dfa state at the entry of the bb is not copied
    to the fallthru basic block. However a DEBUG insn is treated as a real
    insn, and if a bb contains non-real insns and a DEBUG insn, it's dfa
    state is copied to the fallthru bb. This was resulting in
    -fcompare-debug failure as the incoming dfa state of the fallthru block
    is different with -g. We should always copy the dfa state of a bb to
    it's fallthru bb even if the bb does not contain real insns.
    
    2022-08-22  Surya Kumari Jangala  <jskumari@linux.ibm.com>
    
    gcc/
            PR rtl-optimization/105586
            * sched-rgn.cc (save_state_for_fallthru_edge): New function.
            (schedule_region): Use it for all blocks.
    
    gcc/testsuite/
            PR rtl-optimization/105586
            * gcc.target/powerpc/pr105586.c: New test.

Diff:
---
 gcc/sched-rgn.cc                            | 37 ++++++++++++++++++-----------
 gcc/testsuite/gcc.target/powerpc/pr105586.c | 19 +++++++++++++++
 2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/gcc/sched-rgn.cc b/gcc/sched-rgn.cc
index 0dc2a8f2851..420c45dffb4 100644
--- a/gcc/sched-rgn.cc
+++ b/gcc/sched-rgn.cc
@@ -3082,6 +3082,27 @@ free_bb_state_array (void)
   bb_state = NULL;
 }
 
+/* If LAST_BB falls through to another block B, record that B should
+   start with DFA start STATE.  */
+
+static void
+save_state_for_fallthru_edge (basic_block last_bb, state_t state)
+{
+  edge f = find_fallthru_edge (last_bb->succs);
+  if (f
+      && (!f->probability.initialized_p ()
+	  || (f->probability.to_reg_br_prob_base () * 100
+	      / REG_BR_PROB_BASE
+	      >= param_sched_state_edge_prob_cutoff)))
+  {
+    memcpy (bb_state[f->dest->index], state,
+	    dfa_state_size);
+    if (sched_verbose >= 5)
+      fprintf (sched_dump, "saving state for edge %d->%d\n",
+	       f->src->index, f->dest->index);
+  }
+}
+
 /* Schedule a region.  A region is either an inner loop, a loop-free
    subroutine, or a single basic block.  Each bb in the region is
    scheduled after its flow predecessors.  */
@@ -3155,6 +3176,7 @@ schedule_region (int rgn)
       if (no_real_insns_p (head, tail))
 	{
 	  gcc_assert (first_bb == last_bb);
+	  save_state_for_fallthru_edge (last_bb, bb_state[first_bb->index]);
 	  continue;
 	}
 
@@ -3173,26 +3195,13 @@ schedule_region (int rgn)
       curr_bb = first_bb;
       if (dbg_cnt (sched_block))
         {
-	  edge f;
 	  int saved_last_basic_block = last_basic_block_for_fn (cfun);
 
 	  schedule_block (&curr_bb, bb_state[first_bb->index]);
 	  gcc_assert (EBB_FIRST_BB (bb) == first_bb);
 	  sched_rgn_n_insns += sched_n_insns;
 	  realloc_bb_state_array (saved_last_basic_block);
-	  f = find_fallthru_edge (last_bb->succs);
-	  if (f
-	      && (!f->probability.initialized_p ()
-		  || (f->probability.to_reg_br_prob_base () * 100
-		      / REG_BR_PROB_BASE
-		      >= param_sched_state_edge_prob_cutoff)))
-	    {
-	      memcpy (bb_state[f->dest->index], curr_state,
-		      dfa_state_size);
-	      if (sched_verbose >= 5)
-		fprintf (sched_dump, "saving state for edge %d->%d\n",
-			 f->src->index, f->dest->index);
-	    }
+	  save_state_for_fallthru_edge (last_bb, curr_state);
         }
       else
         {
diff --git a/gcc/testsuite/gcc.target/powerpc/pr105586.c b/gcc/testsuite/gcc.target/powerpc/pr105586.c
new file mode 100644
index 00000000000..bd397f58bc0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr105586.c
@@ -0,0 +1,19 @@
+/* { dg-options "-mdejagnu-tune=power4 -O2 -fcompare-debug -fno-if-conversion -fno-guess-branch-probability" } */
+
+extern int bar(int i);
+
+typedef unsigned long u64;
+int g;
+
+__int128 h;
+
+void
+foo(int a, int b) {
+  int i;
+  char u8_1 = g, u8_3 = a;
+  u64 u64_1 = bar(0), u64_3 = u8_3 * u64_1;
+  __int128 u128_1 = h ^ __builtin_expect(i, 0);
+  u64 u64_4 = u64_1 << ((__builtin_sub_overflow_p(0, u8_1, (u64)0) ^ u128_1) & 8);
+  u64 u64_r = b + u64_3 + u64_4;
+  bar((short)u64_r + u8_3);
+}