Feed results of IPA-CP into tree value numbering

PRs 68930 and 92497 show that when IPA-CP figures out constants in
aggregate parameters or when passed by reference but the loads happen
in an inlined function the information is lost.  This happens even
when the inlined function itself was known to have - or even cloned to
have - such constants in incoming parameters because the transform
phase of IPA passes is not run on them.  See discussion in the bugs
for reasons why.

Honza suggested that we can plug the results of IPA-CP analysis into
value numbering, so that FRE can figure out that some loads fetch
known constants.  This is what this patch attempts to do.  The patch
does not attempt to populate partial_defs with information from
IPA-CP, this can be hopefully added as a follow-up.

gcc/ChangeLog:

2023-08-11  Martin Jambor  <mjambor@suse.cz>

	PR ipa/68930
	PR ipa/92497
	* ipa-prop.h (ipcp_get_aggregate_const): Declare.
	* ipa-prop.cc (ipcp_get_aggregate_const): New function.
	(ipcp_transform_function): Do not deallocate transformation info.
	* tree-ssa-sccvn.cc: Include alloc-pool.h, symbol-summary.h and
	ipa-prop.h.
	(vn_reference_lookup_2): When hitting default-def vuse, query
	IPA-CP transformation info for any known constants.

gcc/testsuite/ChangeLog:

2023-06-07  Martin Jambor  <mjambor@suse.cz>

	PR ipa/68930
	PR ipa/92497
	* gcc.dg/ipa/pr92497-1.c: New test.
	* gcc.dg/ipa/pr92497-2.c: Likewise.

5 files changed, 116 insertions, 6 deletions

diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
index 4f6ed7b..9efaa5c 100644
--- a/gcc/ipa-prop.cc
+++ b/gcc/ipa-prop.cc
@@ -5760,6 +5760,34 @@ ipcp_modif_dom_walker::before_dom_children (basic_block bb)
   return NULL;
 }
 
+/* If IPA-CP discovered a constant in parameter PARM at OFFSET of a given SIZE
+   - whether passed by reference or not is given by BY_REF - return that
+   constant.  Otherwise return NULL_TREE.  */
+
+tree
+ipcp_get_aggregate_const (struct function *func, tree parm, bool by_ref,
+			  HOST_WIDE_INT bit_offset, HOST_WIDE_INT bit_size)
+{
+  cgraph_node *node = cgraph_node::get (func->decl);
+  ipcp_transformation *ts = ipcp_get_transformation_summary (node);
+
+  if (!ts || !ts->m_agg_values)
+    return NULL_TREE;
+
+  int index = ts->get_param_index (func->decl, parm);
+  if (index < 0)
+    return NULL_TREE;
+
+  ipa_argagg_value_list avl (ts);
+  unsigned unit_offset = bit_offset / BITS_PER_UNIT;
+  tree v = avl.get_value (index, unit_offset, by_ref);
+  if (!v
+      || maybe_ne (tree_to_poly_int64 (TYPE_SIZE (TREE_TYPE (v))), bit_size))
+    return NULL_TREE;
+
+  return v;
+}
+
 /* Return true if we have recorded VALUE and MASK about PARM.
    Set VALUE and MASk accordingly.  */
 
@@ -6031,11 +6059,6 @@ ipcp_transform_function (struct cgraph_node *node)
     free_ipa_bb_info (bi);
   fbi.bb_infos.release ();
 
-  ipcp_transformation *s = ipcp_transformation_sum->get (node);
-  s->m_agg_values = NULL;
-  s->bits = NULL;
-  s->m_vr = NULL;
-
   vec_free (descriptors);
   if (cfg_changed)
     delete_unreachable_blocks_update_callgraph (node, false);
diff --git a/gcc/ipa-prop.h b/gcc/ipa-prop.h
index 410c951..7e033d2 100644
--- a/gcc/ipa-prop.h
+++ b/gcc/ipa-prop.h
@@ -1235,6 +1235,9 @@ void ipa_dump_param (FILE *, class ipa_node_params *info, int i);
 void ipa_release_body_info (struct ipa_func_body_info *);
 tree ipa_get_callee_param_type (struct cgraph_edge *e, int i);
 bool ipcp_get_parm_bits (tree, tree *, widest_int *);
+tree ipcp_get_aggregate_const (struct function *func, tree parm, bool by_ref,
+			       HOST_WIDE_INT bit_offset,
+			       HOST_WIDE_INT bit_size);
 bool unadjusted_ptr_and_unit_offset (tree op, tree *ret,
 				     poly_int64 *offset_ret);
 
diff --git a/gcc/testsuite/gcc.dg/ipa/pr92497-1.c b/gcc/testsuite/gcc.dg/ipa/pr92497-1.c
new file mode 100644
index 0000000..dcece15
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr92497-1.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-early-inlining"  } */
+
+struct a {int a;};
+static int
+foo (struct a a)
+{
+  if (!__builtin_constant_p (a.a))
+    __builtin_abort ();
+  return a.a;
+}
+
+static int __attribute__ ((noinline))
+bar (struct a a)
+{
+  return foo(a);
+}
+
+volatile int r;
+
+int main()
+{
+  struct a a={1};
+  r = bar (a);
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/ipa/pr92497-2.c b/gcc/testsuite/gcc.dg/ipa/pr92497-2.c
new file mode 100644
index 0000000..c64090d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr92497-2.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-early-inlining -fno-ipa-sra"  } */
+
+struct a {int a;};
+static int
+foo (struct a *a)
+{
+  if (!__builtin_constant_p (a->a))
+    __builtin_abort ();
+  return a->a;
+}
+
+static int __attribute__ ((noinline))
+bar (struct a *a)
+{
+  return foo(a);
+}
+
+volatile int r;
+
+int main()
+{
+  struct a a={1};
+  r = bar (&a);
+  return 0;
+}
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index 32e06fa..b167891 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -74,6 +74,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-modref-tree.h"
 #include "ipa-modref.h"
 #include "tree-ssa-sccvn.h"
+#include "alloc-pool.h"
+#include "symbol-summary.h"
+#include "ipa-prop.h"
 
 /* This algorithm is based on the SCC algorithm presented by Keith
    Cooper and L. Taylor Simpson in "SCC-Based Value numbering"
@@ -2327,7 +2330,7 @@ vn_walk_cb_data::push_partial_def (pd_data pd,
    with the current VUSE and performs the expression lookup.  */
 
 static void *
-vn_reference_lookup_2 (ao_ref *op ATTRIBUTE_UNUSED, tree vuse, void *data_)
+vn_reference_lookup_2 (ao_ref *op, tree vuse, void *data_)
 {
   vn_walk_cb_data *data = (vn_walk_cb_data *)data_;
   vn_reference_t vr = data->vr;
@@ -2361,6 +2364,35 @@ vn_reference_lookup_2 (ao_ref *op ATTRIBUTE_UNUSED, tree vuse, void *data_)
       return *slot;
     }
 
+  if (SSA_NAME_IS_DEFAULT_DEF (vuse))
+    {
+      HOST_WIDE_INT op_offset, op_size;
+      tree v = NULL_TREE;
+      tree base = ao_ref_base (op);
+
+      if (base
+	  && op->offset.is_constant (&op_offset)
+	  && op->size.is_constant (&op_size)
+	  && op->max_size_known_p ()
+	  && known_eq (op->size, op->max_size))
+	{
+	  if (TREE_CODE (base) == PARM_DECL)
+	    v = ipcp_get_aggregate_const (cfun, base, false, op_offset,
+					  op_size);
+	  else if (TREE_CODE (base) == MEM_REF
+		   && integer_zerop (TREE_OPERAND (base, 1))
+		   && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME
+		   && SSA_NAME_IS_DEFAULT_DEF (TREE_OPERAND (base, 0))
+		   && (TREE_CODE (SSA_NAME_VAR (TREE_OPERAND (base, 0)))
+		       == PARM_DECL))
+	    v = ipcp_get_aggregate_const (cfun,
+					  SSA_NAME_VAR (TREE_OPERAND (base, 0)),
+					  true, op_offset, op_size);
+	}
+      if (v)
+	return data->finish (vr->set, vr->base_set, v);
+    }
+
   return NULL;
 }