Support EAF_NOT_RETURNED in tree-ssa-structalias

gcc/ChangeLog:

2021-07-17  Jan Hubicka  <hubicka@ucw.cz>

	* tree-ssa-structalias.c (handle_rhs_call): Support EAF_NOT_RETURNED.
	(handle_const_call): Liekise
	(handle_pure_call): Liekise

gcc/testsuite/ChangeLog:

2021-07-17  Jan Hubicka  <hubicka@ucw.cz>

	* gcc.dg/tree-ssa/modref-6.c: New test.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/modref-6.c b/gcc/testsuite/gcc.dg/tree-ssa/modref-6.c
new file mode 100644 (file)
index 0000000..8db9a1d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/modref-6.c
@@ -0,0 +1,37 @@
+/* { dg-options "-O2 -fdump-tree-modref1 -fdump-tree-optimized"  } */
+/* { dg-do compile } */
+int c;
+__attribute__ ((noinline))
+int *test (int *b)
+{
+  c++;
+  return *b ? &c : 0;
+}
+__attribute__ ((noinline, pure))
+int *pure_test (int *b)
+{
+  return *b && c ? &c : 0;
+}
+__attribute__ ((noinline, const))
+int *const_test (int *b)
+{
+  return b ? &c : 0;
+}
+void escape (int *);
+
+int test2()
+{
+   int a = 42;
+   escape (test (&a));
+   escape (pure_test (&a));
+   escape (const_test (&a));
+   return a;
+}
+/* Flags for normal call.  */
+/* { dg-final { scan-tree-dump "parm 0 flags: direct noclobber noescape nodirectescape not_returned" "modref1"  } } */
+/* Flags for pure call.  */
+/* { dg-final { scan-tree-dump "parm 0 flags: direct not_returned" "modref1"  } } */
+/* Flags for const call.  */
+/* { dg-final { scan-tree-dump "parm 0 flags: unused not_returned" "modref1"  } } */
+/* Overall we want to make "int a" non escaping.  */
+/* { dg-final { scan-tree-dump "return 42" "optimized"  } } */

diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
index 7163438..71894b3 100644 (file)
--- a/gcc/tree-ssa-structalias.c
+++ b/gcc/tree-ssa-structalias.c
@@ -4082,9 +4082,12 @@ handle_rhs_call (gcall *stmt, vec<ce_s> *results)
          if (!(flags & EAF_DIRECT))
            make_transitive_closure_constraints (tem);
          make_copy_constraint (uses, tem->id);
+         /* TODO: This is overly conservative when some parameters are
+            returned while others are not.  */
+         if (!(flags & EAF_NOT_RETURNED))
+           returns_uses = true;
          if (!(flags & (EAF_NOESCAPE | EAF_DIRECT)))
            make_indirect_escape_constraint (tem);
-         returns_uses = true;
        }
       else if (flags & (EAF_NOESCAPE | EAF_NODIRECTESCAPE))
        {
@@ -4098,6 +4101,8 @@ handle_rhs_call (gcall *stmt, vec<ce_s> *results)
          if (!(flags & EAF_DIRECT))
            make_transitive_closure_constraints (tem);
          make_copy_constraint (uses, tem->id);
+         if (!(flags & EAF_NOT_RETURNED))
+           returns_uses = true;
          make_copy_constraint (clobbers, tem->id);
          /* Add *tem = nonlocal, do not add *tem = callused as
             EAF_NOESCAPE parameters do not escape to other parameters
@@ -4111,7 +4116,6 @@ handle_rhs_call (gcall *stmt, vec<ce_s> *results)
          process_constraint (new_constraint (lhs, rhs));
          if (!(flags & (EAF_NOESCAPE | EAF_DIRECT)))
            make_indirect_escape_constraint (tem);
-         returns_uses = true;
        }
       else
        make_escape_constraint (arg);
@@ -4261,13 +4265,18 @@ handle_const_call (gcall *stmt, vec<ce_s> *results)
 
   /* May return offsetted arguments.  */
   varinfo_t tem = NULL;
-  if (gimple_call_num_args (stmt) != 0)
-    {
-      tem = new_var_info (NULL_TREE, "callarg", true);
-      tem->is_reg_var = true;
-    }
   for (k = 0; k < gimple_call_num_args (stmt); ++k)
     {
+      int flags = gimple_call_arg_flags (stmt, k);
+
+      /* If the argument is not used or not returned we can ignore it.  */
+      if (flags & (EAF_UNUSED | EAF_NOT_RETURNED))
+       continue;
+      if (!tem)
+       {
+         tem = new_var_info (NULL_TREE, "callarg", true);
+         tem->is_reg_var = true;
+       }
       tree arg = gimple_call_arg (stmt, k);
       auto_vec<ce_s> argc;
       get_constraint_for_rhs (arg, &argc);
@@ -4298,6 +4307,7 @@ handle_pure_call (gcall *stmt, vec<ce_s> *results)
   struct constraint_expr rhsc;
   unsigned i;
   varinfo_t uses = NULL;
+  bool record_uses = false;
 
   /* Memory reached from pointer arguments is call-used.  */
   for (i = 0; i < gimple_call_num_args (stmt); ++i)
@@ -4315,6 +4325,8 @@ handle_pure_call (gcall *stmt, vec<ce_s> *results)
          make_transitive_closure_constraints (uses);
        }
       make_constraint_to (uses->id, arg);
+      if (!(flags & EAF_NOT_RETURNED))
+       record_uses = true;
     }
 
   /* The static chain is used as well.  */
@@ -4327,6 +4339,7 @@ handle_pure_call (gcall *stmt, vec<ce_s> *results)
          make_transitive_closure_constraints (uses);
        }
       make_constraint_to (uses->id, gimple_call_chain (stmt));
+      record_uses = true;
     }
 
   /* And if we applied NRV the address of the return slot.  */
@@ -4343,10 +4356,11 @@ handle_pure_call (gcall *stmt, vec<ce_s> *results)
       auto_vec<ce_s> tmpc;
       get_constraint_for_address_of (gimple_call_lhs (stmt), &tmpc);
       make_constraints_to (uses->id, tmpc);
+      record_uses = true;
     }
 
   /* Pure functions may return call-used and nonlocal memory.  */
-  if (uses)
+  if (record_uses)
     {
       rhsc.var = uses->id;
       rhsc.offset = 0;