[gcc r14-2853] c++: devirtualization of array destruction [PR110057]

[gcc r14-2853] c++: devirtualization of array destruction [PR110057]

[Jason Merrill]

https://gcc.gnu.org/g:a47e615fbf9c6f4b24e5032df5d720b6bf9b63b5

commit r14-2853-ga47e615fbf9c6f4b24e5032df5d720b6bf9b63b5
Author: Ng YongXiang <yongxiangng@gmail.com>
Date:   Thu Jul 27 08:06:14 2023 +0800

    c++: devirtualization of array destruction [PR110057]
    
            PR c++/110057
            PR ipa/83054
    
    gcc/cp/ChangeLog:
    
            * init.cc (build_vec_delete_1): Devirtualize array destruction.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/warn/pr83054.C: Remove devirtualization warning.
            * g++.dg/lto/pr89335_0.C: Likewise.
            * g++.dg/tree-ssa/devirt-array-destructor-1.C: New test.
            * g++.dg/tree-ssa/devirt-array-destructor-2.C: New test.
            * g++.dg/warn/pr83054-2.C: New test.
    
    Signed-off-by: Ng Yong Xiang <yongxiangng@gmail.com>

Diff:
---
 gcc/cp/init.cc                                     | 11 ++++--
 gcc/testsuite/g++.dg/lto/pr89335_0.C               |  2 +-
 .../g++.dg/tree-ssa/devirt-array-destructor-1.C    | 28 ++++++++++++++
 .../g++.dg/tree-ssa/devirt-array-destructor-2.C    | 29 ++++++++++++++
 gcc/testsuite/g++.dg/warn/pr83054-2.C              | 44 ++++++++++++++++++++++
 gcc/testsuite/g++.dg/warn/pr83054.C                |  2 +-
 6 files changed, 110 insertions(+), 6 deletions(-)

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index ff5014ca576..3b9a7783391 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -4116,8 +4116,8 @@ build_vec_delete_1 (location_t loc, tree base, tree maxindex, tree type,
       if (type_build_dtor_call (type))
 	{
 	  tmp = build_delete (loc, ptype, base, sfk_complete_destructor,
-			      LOOKUP_NORMAL|LOOKUP_DESTRUCTOR, 1,
-			      complain);
+			      LOOKUP_NORMAL|LOOKUP_DESTRUCTOR|LOOKUP_NONVIRTUAL,
+			      1, complain);
 	  if (tmp == error_mark_node)
 	    return error_mark_node;
 	}
@@ -4146,9 +4146,12 @@ build_vec_delete_1 (location_t loc, tree base, tree maxindex, tree type,
   if (tmp == error_mark_node)
     return error_mark_node;
   body = build_compound_expr (loc, body, tmp);
+  /* [expr.delete]/3: "In an array delete expression, if the dynamic type of
+     the object to be deleted is not similar to its static type, the behavior
+     is undefined."  So we can set LOOKUP_NONVIRTUAL.  */
   tmp = build_delete (loc, ptype, tbase, sfk_complete_destructor,
-		      LOOKUP_NORMAL|LOOKUP_DESTRUCTOR, 1,
-		      complain);
+		      LOOKUP_NORMAL|LOOKUP_DESTRUCTOR|LOOKUP_NONVIRTUAL,
+		      1, complain);
   if (tmp == error_mark_node)
     return error_mark_node;
   body = build_compound_expr (loc, body, tmp);
diff --git a/gcc/testsuite/g++.dg/lto/pr89335_0.C b/gcc/testsuite/g++.dg/lto/pr89335_0.C
index 95bf4b3b0cb..76382f8d742 100644
--- a/gcc/testsuite/g++.dg/lto/pr89335_0.C
+++ b/gcc/testsuite/g++.dg/lto/pr89335_0.C
@@ -9,7 +9,7 @@ public:
   virtual ~Container ();
 };
 
-class List : public Container // { dg-lto-message "final would enable devirtualization" }
+class List : public Container
 {
 };
 
diff --git a/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-1.C b/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-1.C
new file mode 100644
index 00000000000..ce8dc2a57cd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-1.C
@@ -0,0 +1,28 @@
+// PR c++/110057
+/* { dg-do-compile } */
+/* Virtual calls should be devirtualized because we know dynamic type of object in array at compile time */
+/* { dg-options "-O3 -fdump-tree-optimized -fno-inline"  } */
+
+class A
+{
+public:
+  virtual ~A()
+  {
+  }
+};
+
+class B : public A
+{
+public:
+  virtual ~B()
+  {
+  }
+};
+
+int main()
+{
+  B b[10];
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
diff --git a/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-2.C b/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-2.C
new file mode 100644
index 00000000000..6b44dc1a4ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/devirt-array-destructor-2.C
@@ -0,0 +1,29 @@
+// PR c++/110057
+/* { dg-do-compile } */
+/* Virtual calls should be devirtualized because we know dynamic type of object in array at compile time */
+/* { dg-options "-O3 -fdump-tree-optimized -fno-inline"  } */
+
+class A
+{
+public:
+  virtual ~A()
+  {
+  }
+};
+
+class B : public A
+{
+public:
+  virtual ~B()
+  {
+  }
+};
+
+int main()
+{
+  B* ptr = new B[10];
+  delete[] ptr;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
diff --git a/gcc/testsuite/g++.dg/warn/pr83054-2.C b/gcc/testsuite/g++.dg/warn/pr83054-2.C
new file mode 100644
index 00000000000..6d8216d229f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/pr83054-2.C
@@ -0,0 +1,44 @@
+// PR ipa/83054
+// { dg-options "-O3 -Wsuggest-final-types" }
+// { dg-do compile }
+
+// A throwing dtor in C++98 mode changes the warning.
+#if __cplusplus < 201100L
+#define NOTHROW throw()
+#else
+#define NOTHROW noexcept
+#endif
+
+extern "C" int printf (const char *, ...);
+struct foo // { dg-warning "final would enable devirtualization of 1 call" }
+{
+  static int count;
+  void print (int i, int j) { printf ("foo[%d][%d] = %d\n", i, j, x); }
+  int x;
+  foo () {
+    x = count++;
+    printf("this %d = %x\n", x, (void *)this);
+  }
+  virtual ~foo () NOTHROW {
+    printf("this %d = %x\n", x, (void *)this);
+    --count;
+  }
+};
+int foo::count;
+
+
+int main ()
+{
+  foo *arr[9];
+  for (int i = 0; i < 9; ++i)
+    arr[i] = new foo();
+  if (foo::count != 9)
+    return 1;
+  for (int i = 0; i < 9; ++i)
+    arr[i]->print(i / 3, i % 3);
+  for (int i = 0; i < 9; ++i)
+    delete arr[i];
+  if (foo::count != 0)
+    return 1;
+  return 0;
+}
diff --git a/gcc/testsuite/g++.dg/warn/pr83054.C b/gcc/testsuite/g++.dg/warn/pr83054.C
index 5285f94acee..5a4a6abe248 100644
--- a/gcc/testsuite/g++.dg/warn/pr83054.C
+++ b/gcc/testsuite/g++.dg/warn/pr83054.C
@@ -10,7 +10,7 @@
 #endif
 
 extern "C" int printf (const char *, ...);
-struct foo // { dg-warning "final would enable devirtualization of 5 calls" }
+struct foo
 {
   static int count;
   void print (int i, int j) { printf ("foo[%d][%d] = %d\n", i, j, x); }