make use of CALL_FROM_NEW_OR_DELETE_P

This fixes points-to analysis and DCE to only consider new/delete
operator calls from new or delete expressions and not direct calls.

2020-10-01  Richard Biener  <rguenther@suse.de>

	* gimple.h (GF_CALL_FROM_NEW_OR_DELETE): New call flag.
	(gimple_call_set_from_new_or_delete): New.
	(gimple_call_from_new_or_delete): Likewise.
	* gimple.c (gimple_build_call_from_tree): Set
	GF_CALL_FROM_NEW_OR_DELETE appropriately.
	* ipa-icf-gimple.c (func_checker::compare_gimple_call):
	Compare gimple_call_from_new_or_delete.
	* tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Make
	sure to only consider new/delete calls from new or delete
	expressions.
	(propagate_necessity): Likewise.
	(eliminate_unnecessary_stmts): Likewise.
	* tree-ssa-structalias.c (find_func_aliases_for_call):
	Likewise.

	* g++.dg/tree-ssa/pta-delete-1.C: New testcase.

gcc/gimple.c

@@ -387,6 +387,10 @@ gimple_build_call_from_tree (tree t, tree fnptrtype)
       && fndecl_built_in_p (fndecl, BUILT_IN_NORMAL)
       && ALLOCA_FUNCTION_CODE_P (DECL_FUNCTION_CODE (fndecl)))
     gimple_call_set_alloca_for_var (call, CALL_ALLOCA_FOR_VAR_P (t));
+  else if (fndecl
+	   && (DECL_IS_OPERATOR_NEW_P (fndecl)
+	       || DECL_IS_OPERATOR_DELETE_P (fndecl)))
+    gimple_call_set_from_new_or_delete (call, CALL_FROM_NEW_OR_DELETE_P (t));
   else
     gimple_call_set_from_thunk (call, CALL_FROM_THUNK_P (t));
   gimple_call_set_va_arg_pack (call, CALL_EXPR_VA_ARG_PACK (t));

gcc/gimple.h

@@ -149,6 +149,7 @@ enum gf_mask {
     GF_CALL_MUST_TAIL_CALL	= 1 << 9,
     GF_CALL_BY_DESCRIPTOR	= 1 << 10,
     GF_CALL_NOCF_CHECK		= 1 << 11,
+    GF_CALL_FROM_NEW_OR_DELETE	= 1 << 12,
     GF_OMP_PARALLEL_COMBINED	= 1 << 0,
     GF_OMP_TASK_TASKLOOP	= 1 << 0,
     GF_OMP_TASK_TASKWAIT	= 1 << 1,
@@ -3387,6 +3388,29 @@ gimple_call_from_thunk_p (gcall *s)
 }
 
 
+/* If FROM_NEW_OR_DELETE_P is true, mark GIMPLE_CALL S as being a call
+   to operator new or delete created from a new or delete expression.  */
+
+static inline void
+gimple_call_set_from_new_or_delete (gcall *s, bool from_new_or_delete_p)
+{
+  if (from_new_or_delete_p)
+    s->subcode |= GF_CALL_FROM_NEW_OR_DELETE;
+  else
+    s->subcode &= ~GF_CALL_FROM_NEW_OR_DELETE;
+}
+
+
+/* Return true if GIMPLE_CALL S is a call to operator new or delete from
+   from a new or delete expression.  */
+
+static inline bool
+gimple_call_from_new_or_delete (gcall *s)
+{
+  return (s->subcode & GF_CALL_FROM_NEW_OR_DELETE) != 0;
+}
+
+
 /* If PASS_ARG_PACK_P is true, GIMPLE_CALL S is a stdarg call that needs the
    argument pack in its argument list.  */
 

gcc/ipa-icf-gimple.c

@@ -556,6 +556,7 @@ func_checker::compare_gimple_call (gcall *s1, gcall *s2)
       || gimple_call_tail_p (s1) != gimple_call_tail_p (s2)
       || gimple_call_return_slot_opt_p (s1) != gimple_call_return_slot_opt_p (s2)
       || gimple_call_from_thunk_p (s1) != gimple_call_from_thunk_p (s2)
+      || gimple_call_from_new_or_delete (s1) != gimple_call_from_new_or_delete (s2)
       || gimple_call_va_arg_pack_p (s1) != gimple_call_va_arg_pack_p (s2)
       || gimple_call_alloca_for_var_p (s1) != gimple_call_alloca_for_var_p (s2))
     return false;

gcc/testsuite/g++.dg/tree-ssa/pta-delete-1.C

@@ -0,0 +1,24 @@
+// { dg-do run }
+// { dg-options "-O2" }
+
+struct X {
+  static struct X saved;
+  int *p;
+  X() { __builtin_memcpy (this, &saved, sizeof (X)); }
+};
+X X::saved;
+void __attribute__((noinline)) operator delete (void *p)
+{
+  __builtin_memcpy (&X::saved, p, sizeof (X));
+}
+int main()
+{
+  int y = 1;
+  X *p = new X;
+  p->p = &y;
+  ::operator delete (p);
+  X *q = new X;
+  *(q->p) = 2;
+  if (y != 2)
+    __builtin_abort ();
+}

gcc/tree-ssa-dce.c

@@ -593,9 +593,9 @@ mark_all_reaching_defs_necessary_1 (ao_ref *ref ATTRIBUTE_UNUSED,
 
   /* We want to skip statments that do not constitute stores but have
      a virtual definition.  */
-  if (is_gimple_call (def_stmt))
+  if (gcall *call = dyn_cast <gcall *> (def_stmt))
     {
-      tree callee = gimple_call_fndecl (def_stmt);
+      tree callee = gimple_call_fndecl (call);
       if (callee != NULL_TREE
 	  && fndecl_built_in_p (callee, BUILT_IN_NORMAL))
 	switch (DECL_FUNCTION_CODE (callee))
@@ -612,7 +612,8 @@ mark_all_reaching_defs_necessary_1 (ao_ref *ref ATTRIBUTE_UNUSED,
 
       if (callee != NULL_TREE
 	  && (DECL_IS_REPLACEABLE_OPERATOR_NEW_P (callee)
-	      || DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (callee)))
+	      || DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (callee))
+	  && gimple_call_from_new_or_delete (call))
 	return false;
     }
 
@@ -875,23 +876,25 @@ propagate_necessity (bool aggressive)
 	     processing the argument.  */
 	  bool is_delete_operator
 	    = (is_gimple_call (stmt)
+	       && gimple_call_from_new_or_delete (as_a <gcall *> (stmt))
 	       && gimple_call_replaceable_operator_delete_p (as_a <gcall *> (stmt)));
 	  if (is_delete_operator
 	      || gimple_call_builtin_p (stmt, BUILT_IN_FREE))
 	    {
 	      tree ptr = gimple_call_arg (stmt, 0);
-	      gimple *def_stmt;
+	      gcall *def_stmt;
 	      tree def_callee;
 	      /* If the pointer we free is defined by an allocation
 		 function do not add the call to the worklist.  */
 	      if (TREE_CODE (ptr) == SSA_NAME
-		  && is_gimple_call (def_stmt = SSA_NAME_DEF_STMT (ptr))
+		  && (def_stmt = dyn_cast <gcall *> (SSA_NAME_DEF_STMT (ptr)))
 		  && (def_callee = gimple_call_fndecl (def_stmt))
 		  && ((DECL_BUILT_IN_CLASS (def_callee) == BUILT_IN_NORMAL
 		       && (DECL_FUNCTION_CODE (def_callee) == BUILT_IN_ALIGNED_ALLOC
 			   || DECL_FUNCTION_CODE (def_callee) == BUILT_IN_MALLOC
 			   || DECL_FUNCTION_CODE (def_callee) == BUILT_IN_CALLOC))
-		      || DECL_IS_REPLACEABLE_OPERATOR_NEW_P (def_callee)))
+		      || (DECL_IS_REPLACEABLE_OPERATOR_NEW_P (def_callee)
+			  && gimple_call_from_new_or_delete (def_stmt))))
 		{
 		  if (is_delete_operator)
 		    {
@@ -947,9 +950,9 @@ propagate_necessity (bool aggressive)
 	     in 1).  By keeping a global visited bitmap for references
 	     we walk for 2) we avoid quadratic behavior for those.  */
 
-	  if (is_gimple_call (stmt))
+	  if (gcall *call = dyn_cast <gcall *> (stmt))
 	    {
-	      tree callee = gimple_call_fndecl (stmt);
+	      tree callee = gimple_call_fndecl (call);
 	      unsigned i;
 
 	      /* Calls to functions that are merely acting as barriers
@@ -972,22 +975,23 @@ propagate_necessity (bool aggressive)
 
 	      if (callee != NULL_TREE
 		  && (DECL_IS_REPLACEABLE_OPERATOR_NEW_P (callee)
-		      || DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (callee)))
+		      || DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (callee))
+		  && gimple_call_from_new_or_delete (call))
 		continue;
 
 	      /* Calls implicitly load from memory, their arguments
 	         in addition may explicitly perform memory loads.  */
-	      mark_all_reaching_defs_necessary (stmt);
-	      for (i = 0; i < gimple_call_num_args (stmt); ++i)
+	      mark_all_reaching_defs_necessary (call);
+	      for (i = 0; i < gimple_call_num_args (call); ++i)
 		{
-		  tree arg = gimple_call_arg (stmt, i);
+		  tree arg = gimple_call_arg (call, i);
 		  if (TREE_CODE (arg) == SSA_NAME
 		      || is_gimple_min_invariant (arg))
 		    continue;
 		  if (TREE_CODE (arg) == WITH_SIZE_EXPR)
 		    arg = TREE_OPERAND (arg, 0);
 		  if (!ref_may_be_aliased (arg))
-		    mark_aliased_reaching_defs_necessary (stmt, arg);
+		    mark_aliased_reaching_defs_necessary (call, arg);
 		}
 	    }
 	  else if (gimple_assign_single_p (stmt))
@@ -1397,6 +1401,7 @@ eliminate_unnecessary_stmts (void)
 	  if (gimple_plf (stmt, STMT_NECESSARY)
 	      && (gimple_call_builtin_p (stmt, BUILT_IN_FREE)
 		  || (is_gimple_call (stmt)
+		      && gimple_call_from_new_or_delete (as_a <gcall *> (stmt))
 		      && gimple_call_replaceable_operator_delete_p (as_a <gcall *> (stmt)))))
 	    {
 	      tree ptr = gimple_call_arg (stmt, 0);

gcc/tree-ssa-structalias.c

@@ -4857,7 +4857,13 @@ find_func_aliases_for_call (struct function *fn, gcall *t)
 	 point for reachable memory of their arguments.  */
       else if (flags & (ECF_PURE|ECF_LOOPING_CONST_OR_PURE))
 	handle_pure_call (t, &rhsc);
-      else if (fndecl && DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (fndecl))
+      /* If the call is to a replaceable operator delete and results
+	 from a delete expression as opposed to a direct call to
+	 such operator, then the effects for PTA (in particular
+	 the escaping of the pointer) can be ignored.  */
+      else if (fndecl
+	       && DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (fndecl)
+	       && gimple_call_from_new_or_delete (t))
 	;
       else
 	handle_rhs_call (t, &rhsc);