ipa-sra: Move caller->callee propagation before callee->caller one

This patch does not do any functional changes, it merely moves
top-down propagation in the IPA-SRA WPA phase before bottom-up one.
This also meant moving some preliminary checks from the latter to the
former - where they need to be in their own loop over each SCC because
the subsequent one looks at callers.

Currently the propagations are independent (top-down is used for
return value rermoval, bottom-up for parameter removal and splitting)
but subsequent patches will introduce flags about parameters which
should be propagated from callers first and used in splitting.  I
separated this change to test ir independently and make those
subsequent patches cleaner.

While at it, I also replaced couple of FOR_EACH_VEC_ELT macros with
C++11 style iteration.

gcc/ChangeLog:

2022-11-11  Martin Jambor  <mjambor@suse.cz>

	* ipa-sra.cc (ipa_sra_analysis): Move top-down analysis before
	bottom-up analysis.  Replace FOR_EACH_VEC_ELT with C++11 iteration.

gcc/testsuite/ChangeLog:

2021-12-14  Martin Jambor  <mjambor@suse.cz>

	* gcc.dg/ipa/ipa-sra-25.c: New test

2 files changed, 78 insertions, 62 deletions

diff --git a/gcc/ipa-sra.cc b/gcc/ipa-sra.cc
index 866f52e89e0..65d6417a35d 100644
--- a/gcc/ipa-sra.cc
+++ b/gcc/ipa-sra.cc
@@ -3926,27 +3926,74 @@ ipa_sra_analysis (void)
   auto_vec <cgraph_node *, 16> stack;
   int node_scc_count = ipa_reduced_postorder (order, true, NULL);
 
-  /* One sweep from callees to callers for parameter removal and splitting.  */
-  for (int i = 0; i < node_scc_count; i++)
+  /* One sweep from callers to callees for return value removal.  */
+  for (int i = node_scc_count - 1; i >= 0 ; i--)
     {
       cgraph_node *scc_rep = order[i];
       vec<cgraph_node *> cycle_nodes = ipa_get_nodes_in_cycle (scc_rep);
-      unsigned j;
 
-      /* Preliminary IPA function level checks and first step of parameter
-	 removal.  */
-      cgraph_node *v;
-      FOR_EACH_VEC_ELT (cycle_nodes, j, v)
+      /* Preliminary IPA function level checks.  */
+      for (cgraph_node *v : cycle_nodes)
 	{
 	  isra_func_summary *ifs = func_sums->get (v);
 	  if (!ifs || !ifs->m_candidate)
 	    continue;
 	  if (!ipa_sra_ipa_function_checks (v)
 	      || check_all_callers_for_issues (v))
-	    {
-	      ifs->zap ();
-	      continue;
-	    }
+	    ifs->zap ();
+	}
+
+      for (cgraph_node *v : cycle_nodes)
+	{
+	  isra_func_summary *ifs = func_sums->get (v);
+	  if (!ifs || !ifs->m_candidate)
+	    continue;
+	  bool return_needed
+	    = (ifs->m_returns_value
+	       && (!dbg_cnt (ipa_sra_retvalues)
+		   || v->call_for_symbol_and_aliases (retval_used_p,
+						      NULL, true)));
+	  ifs->m_return_ignored = !return_needed;
+	  if (return_needed)
+	    isra_push_node_to_stack (v, ifs, &stack);
+	}
+
+      while (!stack.is_empty ())
+	{
+	  cgraph_node *node = stack.pop ();
+	  isra_func_summary *ifs = func_sums->get (node);
+	  gcc_checking_assert (ifs && ifs->m_queued);
+	  ifs->m_queued = false;
+
+	  for (cgraph_edge *cs = node->callees; cs; cs = cs->next_callee)
+	    if (ipa_edge_within_scc (cs)
+		&& call_sums->get (cs)->m_return_returned)
+	      {
+		enum availability av;
+		cgraph_node *callee = cs->callee->function_symbol (&av);
+		isra_func_summary *to_ifs = func_sums->get (callee);
+		if (to_ifs && to_ifs->m_return_ignored)
+		  {
+		    to_ifs->m_return_ignored = false;
+		    isra_push_node_to_stack (callee, to_ifs, &stack);
+		  }
+	      }
+	}
+      cycle_nodes.release ();
+    }
+
+  /* One sweep from callees to callers for parameter removal and splitting.  */
+  for (int i = 0; i < node_scc_count; i++)
+    {
+      cgraph_node *scc_rep = order[i];
+      vec<cgraph_node *> cycle_nodes = ipa_get_nodes_in_cycle (scc_rep);
+
+      /* First step of parameter removal.  */
+      for (cgraph_node *v : cycle_nodes)
+	{
+	  isra_func_summary *ifs = func_sums->get (v);
+	  if (!ifs || !ifs->m_candidate)
+	    continue;
 	  if (disable_unavailable_parameters (v, ifs))
 	    continue;
 	  for (cgraph_edge *cs = v->indirect_calls; cs; cs = cs->next_callee)
@@ -3959,7 +4006,7 @@ ipa_sra_analysis (void)
       /* Look at edges within the current SCC and propagate used-ness across
 	 them, pushing onto the stack all notes which might need to be
 	 revisited.  */
-      FOR_EACH_VEC_ELT (cycle_nodes, j, v)
+      for (cgraph_node *v : cycle_nodes)
 	v->call_for_symbol_thunks_and_aliases (propagate_used_to_scc_callers,
 					       &stack, true);
 
@@ -3980,7 +4027,7 @@ ipa_sra_analysis (void)
       do
 	{
 	  repeat_scc_access_propagation = false;
-	  FOR_EACH_VEC_ELT (cycle_nodes, j, v)
+	  for (cgraph_node *v : cycle_nodes)
 	    {
 	      isra_func_summary *ifs = func_sums->get (v);
 	      if (!ifs
@@ -3995,60 +4042,12 @@ ipa_sra_analysis (void)
       while (repeat_scc_access_propagation);
 
       if (flag_checking)
-	FOR_EACH_VEC_ELT (cycle_nodes, j, v)
+	for (cgraph_node *v : cycle_nodes)
 	  verify_splitting_accesses (v, true);
 
       cycle_nodes.release ();
     }
 
-  /* One sweep from caller to callees for result removal.  */
-  for (int i = node_scc_count - 1; i >= 0 ; i--)
-    {
-      cgraph_node *scc_rep = order[i];
-      vec<cgraph_node *> cycle_nodes = ipa_get_nodes_in_cycle (scc_rep);
-      unsigned j;
-
-      cgraph_node *v;
-      FOR_EACH_VEC_ELT (cycle_nodes, j, v)
-	{
-	  isra_func_summary *ifs = func_sums->get (v);
-	  if (!ifs || !ifs->m_candidate)
-	    continue;
-
-	  bool return_needed
-	    = (ifs->m_returns_value
-	       && (!dbg_cnt (ipa_sra_retvalues)
-		   || v->call_for_symbol_and_aliases (retval_used_p,
-						      NULL, true)));
-	  ifs->m_return_ignored = !return_needed;
-	  if (return_needed)
-	    isra_push_node_to_stack (v, ifs, &stack);
-	}
-
-      while (!stack.is_empty ())
-	{
-	  cgraph_node *node = stack.pop ();
-	  isra_func_summary *ifs = func_sums->get (node);
-	  gcc_checking_assert (ifs && ifs->m_queued);
-	  ifs->m_queued = false;
-
-	  for (cgraph_edge *cs = node->callees; cs; cs = cs->next_callee)
-	    if (ipa_edge_within_scc (cs)
-		&& call_sums->get (cs)->m_return_returned)
-	      {
-		enum availability av;
-		cgraph_node *callee = cs->callee->function_symbol (&av);
-		isra_func_summary *to_ifs = func_sums->get (callee);
-		if (to_ifs && to_ifs->m_return_ignored)
-		  {
-		    to_ifs->m_return_ignored = false;
-		    isra_push_node_to_stack (callee, to_ifs, &stack);
-		  }
-	      }
-	}
-      cycle_nodes.release ();
-    }
-
   ipa_free_postorder_info ();
   free (order);
 
diff --git a/gcc/testsuite/gcc.dg/ipa/ipa-sra-25.c b/gcc/testsuite/gcc.dg/ipa/ipa-sra-25.c
new file mode 100644
index 00000000000..46fc1a54571
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/ipa-sra-25.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wmaybe-uninitialized -Werror"  } */
+
+int cbos();
+static int aos() {
+  cbos();
+  return 0;
+}
+int cbos_ptr;
+long cbos_psize;
+int cbos() {
+  if (cbos_ptr)
+    return aos();
+  if (cbos_psize)
+    return 1;
+  return 0;
+}