[05/10] __builtin_dynamic_object_size: Recognize builtin

diff --git a/gcc/builtins.c b/gcc/builtins.c
index d2e6d95a175..9135d553c87 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -178,7 +178,7 @@  static rtx expand_builtin_memory_chk (tree, rtx, machine_mode,
 				      enum built_in_function);
 static void maybe_emit_chk_warning (tree, enum built_in_function);
 static void maybe_emit_sprintf_chk_warning (tree, enum built_in_function);
-static tree fold_builtin_object_size (tree, tree);
+static tree fold_builtin_object_size (tree, tree, enum built_in_function);
 
 unsigned HOST_WIDE_INT target_newline;
 unsigned HOST_WIDE_INT target_percent;
@@ -7880,6 +7880,7 @@  expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
       return const0_rtx;
 
     case BUILT_IN_OBJECT_SIZE:
+    case BUILT_IN_DYNAMIC_OBJECT_SIZE:
       return expand_builtin_object_size (exp);
 
     case BUILT_IN_MEMCPY_CHK:
@@ -9286,7 +9287,8 @@  fold_builtin_2 (location_t loc, tree expr, tree fndecl, tree arg0, tree arg1)
       break;
 
     case BUILT_IN_OBJECT_SIZE:
-      return fold_builtin_object_size (arg0, arg1);
+    case BUILT_IN_DYNAMIC_OBJECT_SIZE:
+      return fold_builtin_object_size (arg0, arg1, fcode);
 
     case BUILT_IN_ATOMIC_ALWAYS_LOCK_FREE:
       return fold_builtin_atomic_always_lock_free (arg0, arg1);
@@ -10224,7 +10226,7 @@  maybe_emit_sprintf_chk_warning (tree exp, enum built_in_function fcode)
    if possible.  */
 
 static tree
-fold_builtin_object_size (tree ptr, tree ost)
+fold_builtin_object_size (tree ptr, tree ost, enum built_in_function fcode)
 {
   tree bytes;
   int object_size_type;
@@ -10250,7 +10252,8 @@  fold_builtin_object_size (tree ptr, tree ost)
 
   if (TREE_CODE (ptr) == ADDR_EXPR)
     {
-      compute_builtin_object_size (ptr, object_size_type, &bytes);
+      compute_builtin_object_size (ptr, object_size_type, &bytes,
+				   fcode == BUILT_IN_DYNAMIC_OBJECT_SIZE);
       return fold_convert (size_type_node, bytes);
     }
   else if (TREE_CODE (ptr) == SSA_NAME)
@@ -10258,7 +10261,8 @@  fold_builtin_object_size (tree ptr, tree ost)
       /* If object size is not known yet, delay folding until
        later.  Maybe subsequent passes will help determining
        it.  */
-      if (compute_builtin_object_size (ptr, object_size_type, &bytes))
+      if (compute_builtin_object_size (ptr, object_size_type, &bytes,
+				       fcode == BUILT_IN_DYNAMIC_OBJECT_SIZE))
 	return fold_convert (size_type_node, bytes);
     }
 
diff --git a/gcc/builtins.def b/gcc/builtins.def
index 45a09b4d42d..2b2c46e9df6 100644
--- a/gcc/builtins.def
+++ b/gcc/builtins.def
@@ -972,6 +972,7 @@  DEF_BUILTIN_STUB (BUILT_IN_STRNCMP_EQ, "__builtin_strncmp_eq")
 
 /* Object size checking builtins.  */
 DEF_GCC_BUILTIN	       (BUILT_IN_OBJECT_SIZE, "object_size", BT_FN_SIZE_CONST_PTR_INT, ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN	       (BUILT_IN_DYNAMIC_OBJECT_SIZE, "dynamic_object_size", BT_FN_SIZE_CONST_PTR_INT, ATTR_NOTHROW_LEAF_LIST)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMCPY_CHK, "__memcpy_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_NOTHROW_NONNULL_LEAF)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMMOVE_CHK, "__memmove_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_NOTHROW_NONNULL_LEAF)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMPCPY_CHK, "__mempcpy_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_RETNONNULL_NOTHROW_LEAF)
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index eee4c6737bb..7fe244ce3c8 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -12712,6 +12712,7 @@  __atomic_store_n(&lockvar, 0, __ATOMIC_RELEASE|__ATOMIC_HLE_RELEASE);
 @node Object Size Checking
 @section Object Size Checking Built-in Functions
 @findex __builtin_object_size
+@findex __builtin_dynamic_object_size
 @findex __builtin___memcpy_chk
 @findex __builtin___mempcpy_chk
 @findex __builtin___memmove_chk
@@ -12779,6 +12780,18 @@  assert (__builtin_object_size (q, 1) == sizeof (var.b));
 @end smallexample
 @end deftypefn
 
+@deftypefn {Built-in Function} {size_t} __builtin_dynamic_object_size (const void * @var{ptr}, int @var{type})
+is similar to @code{__builtin_object_size} in that it returns a number of bytes
+from @var{ptr} to the end of the object @var{ptr} pointer points to, except
+that the size returned may not be a constant.  This results in successful
+evaluation of object size estimates in a wider range of use cases and can be
+more precise than @code{__builtin_object_size}, but it incurs a performance
+penalty since it may add a runtime overhead on size computation.  Semantics of
+@var{type} as well as return values in case it is not possible to determine
+which objects @var{ptr} points to at compile time are the same as in the case
+of @code{__builtin_object_size}.
+@end deftypefn
+
 There are built-in functions added for many common string operation
 functions, e.g., for @code{memcpy} @code{__builtin___memcpy_chk}
 built-in is provided.  This built-in has an additional last argument,
diff --git a/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size1.C b/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size1.C
new file mode 100644
index 00000000000..b11ac200751
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size1.C
@@ -0,0 +1,5 @@ 
+// { dg-do run }
+// { dg-options "-O2" }
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size1.C"
diff --git a/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size2.C b/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size2.C
new file mode 100644
index 00000000000..6e52cf38533
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/builtin-dynamic-object-size2.C
@@ -0,0 +1,5 @@ 
+// { dg-do run }
+// { dg-options "-O2" }
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size2.C"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-alloc-size.c b/gcc/testsuite/gcc.dg/builtin-dynamic-alloc-size.c
new file mode 100644
index 00000000000..9d0eadd6be4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-alloc-size.c
@@ -0,0 +1,7 @@ 
+/* { dg-do compile }
+   { dg-require-effective-target alloca }
+   { dg-additional-options "-O2 -fdump-tree-optimized" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-alloc-size.c"
+/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-1.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-1.c
new file mode 100644
index 00000000000..7cc8b1c9488
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-1.c
@@ -0,0 +1,6 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target alloca } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-1.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-10.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-10.c
new file mode 100644
index 00000000000..bc880a589ae
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-10.c
@@ -0,0 +1,9 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-early_objsz-details" } */
+// { dg-skip-if "packed attribute missing for drone_source_packet" { "epiphany-*-*" } }
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-10.c"
+
+/* { dg-final { scan-tree-dump "maximum object size 21" "early_objsz" } } */
+/* { dg-final { scan-tree-dump "maximum subobject size 16" "early_objsz" } } */
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-11.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-11.c
new file mode 100644
index 00000000000..65dcec9fcae
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-11.c
@@ -0,0 +1,7 @@ 
+/* PR48985 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu89" } */
+/* { dg-skip-if "packed attribute missing for struct s" { "epiphany-*-*" } } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-11.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-12.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-12.c
new file mode 100644
index 00000000000..f0ce050a943
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-12.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-12.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-13.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-13.c
new file mode 100644
index 00000000000..555e23522dc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-13.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-13.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-14.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-14.c
new file mode 100644
index 00000000000..26207200191
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-14.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-14.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-15.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-15.c
new file mode 100644
index 00000000000..cd8a941438d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-15.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-15.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-16.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-16.c
new file mode 100644
index 00000000000..5aa256dec1a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-16.c
@@ -0,0 +1,7 @@ 
+/* { dg-do run } */
+/* { dg-options "-O0" } */
+
+#define DYNAMIC_OBJECT_SIZE
+#define __builtin_object_size __builtin_dynamic_object_size
+char ax2[];               /* { dg-warning "assumed to have one element" } */
+#include "builtin-object-size-16.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-17.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-17.c
new file mode 100644
index 00000000000..f4c4b0fbc7a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-17.c
@@ -0,0 +1,8 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O0 -fdump-tree-ssa" } */
+
+#define DYNAMIC_OBJECT_SIZE
+char ax2[];               /* { dg-warning "assumed to have one element" } */
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-17.c"
+/* { dg-final { scan-tree-dump-not "failure_on_line" "ssa" } } */
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-18.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-18.c
new file mode 100644
index 00000000000..70c1ebcff21
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-18.c
@@ -0,0 +1,8 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* __stpncpy_chk could return buf up to buf + 64, so
+   the minimum object size might be far smaller than 64.  */
+/* { dg-final { scan-tree-dump-not "return 64;" "optimized" } } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-18.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-19.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-19.c
new file mode 100644
index 00000000000..44141a38607
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-19.c
@@ -0,0 +1,104 @@ 
+/* PR tree-optimization/88372 - alloc_size attribute is ignored
+   on function pointers { dg-do compile }
+   { dg-options "-O2 -fdump-tree-optimized" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-18.c"
+
+typedef __SIZE_TYPE__ size_t;
+
+#define ATTR(...) __attribute__ ((__VA_ARGS__))
+#define CONCAT(x, y) x ## y
+#define CAT(x, y) CONCAT (x, y)
+#define FAILNAME(name) CAT (call_ ## name ##_on_line_, __LINE__)
+
+#define FAIL(name) do {				\
+    extern void FAILNAME (name) (void);		\
+    FAILNAME (name)();				\
+  } while (0)
+
+/* Macro to emit a call to function named
+   call_in_true_branch_not_eliminated_on_line_NNN()
+   for each call that's expected to be eliminated.  The dg-final
+   scan-tree-dump-time directive at the bottom of the test verifies
+   that no such call appears in output.  */
+#define ELIM(expr)							\
+  if (!(expr)) FAIL (in_true_branch_not_eliminated); else (void)0
+
+void sink (void*);
+
+#define T(alloc, n) do {			\
+    void *p = alloc;				\
+    sink (p);					\
+    ELIM (n == __builtin_object_size (p, 0));	\
+    ELIM (n == __builtin_object_size (p, 1));	\
+    ELIM (n == __builtin_object_size (p, 2));	\
+    ELIM (n == __builtin_object_size (p, 3));	\
+  } while (0)
+
+
+ATTR (alloc_size (1)) void* (*alloc_1_x)(size_t, size_t);
+ATTR (alloc_size (2)) void* (*alloc_x_2)(size_t, size_t);
+
+/* Verify that things work when attribute alloc_size is applied
+   to a typedef that is then used to declared a pointer.  */
+typedef ATTR (alloc_size (1, 2)) void* (alloc_1_2_t)(size_t, size_t);
+
+void test_alloc_ptr (alloc_1_2_t *alloc_1_2)
+{
+  T (alloc_1_x (0, 0), 0);
+  T (alloc_1_x (1, 0), 1);
+  T (alloc_1_x (3, 0), 3);
+  T (alloc_1_x (9, 5), 9);
+
+  T (alloc_x_2 (0, 0), 0);
+  T (alloc_x_2 (1, 0), 0);
+  T (alloc_x_2 (0, 1), 1);
+  T (alloc_x_2 (9, 5), 5);
+
+  T (alloc_1_2 (0, 0), 0);
+  T (alloc_1_2 (1, 0), 0);
+  T (alloc_1_2 (0, 1), 0);
+  T (alloc_1_2 (9, 5), 45);
+}
+
+/* Verify that object size is detected even in indirect calls via
+   function pointers to built-in allocation functions, even without
+   explicit use of attribute alloc_size on the pointers.  */
+
+typedef void *(allocfn_1) (size_t);
+typedef void *(allocfn_1_2) (size_t, size_t);
+
+static inline void *
+call_alloc (allocfn_1 *fn1, allocfn_1_2 *fn2, size_t n1, size_t n2)
+{
+  return fn1 ? fn1 (n1) : fn2 (n1, n2);
+}
+
+static inline void *
+call_malloc (size_t n)
+{
+  return call_alloc (__builtin_malloc, 0, n, 0);
+}
+
+static inline void *
+call_calloc (size_t n1, size_t n2)
+{
+  return call_alloc (0, __builtin_calloc, n1, n2);
+}
+
+void test_builtin_ptr (void)
+{
+  T (call_malloc (0), 0);
+  T (call_malloc (1), 1);
+  T (call_malloc (9), 9);
+
+  T (call_calloc (0, 0), 0);
+  T (call_calloc (0, 1), 0);
+  T (call_calloc (1, 0), 0);
+  T (call_calloc (1, 1), 1);
+  T (call_calloc (1, 3), 3);
+  T (call_calloc (2, 3), 6);
+}
+
+/* { dg-final { scan-tree-dump-not "not_eliminated" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-2.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-2.c
new file mode 100644
index 00000000000..267dbf48ca7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-2.c
@@ -0,0 +1,6 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target alloca } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-2.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-3.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-3.c
new file mode 100644
index 00000000000..fb9dc56da7e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-3.c
@@ -0,0 +1,6 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target alloca } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-3.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-4.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-4.c
new file mode 100644
index 00000000000..870548b4206
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-4.c
@@ -0,0 +1,6 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target alloca } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-4.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-5.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-5.c
new file mode 100644
index 00000000000..698b03c34be
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-5.c
@@ -0,0 +1,7 @@ 
+/* { dg-do compile { target i?86-*-linux* i?86-*-gnu* x86_64-*-linux* } } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-5.c"
+
+/* { dg-final { scan-assembler-not "abort" } } */
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-6.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-6.c
new file mode 100644
index 00000000000..6a275ce5b37
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-6.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-6.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-7.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-7.c
new file mode 100644
index 00000000000..e2a65994687
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-7.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-7.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-8.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-8.c
new file mode 100644
index 00000000000..e7af383d9b6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-8.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-8.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-9.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-9.c
new file mode 100644
index 00000000000..19021bc2ce9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-9.c
@@ -0,0 +1,5 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define __builtin_object_size __builtin_dynamic_object_size
+#include "builtin-object-size-9.c"
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-16.c b/gcc/testsuite/gcc.dg/builtin-object-size-16.c
index 48229390bfd..a4557fbb1fb 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-16.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-16.c
@@ -54,7 +54,9 @@  static int nfails;
 typedef __SIZE_TYPE__ size_t;
 
 extern char ax[];
+#ifndef DYNAMIC_OBJECT_SIZE
 char ax2[];               /* { dg-warning "assumed to have one element" } */
+#endif
 
 extern char a0[0];
 static char a1[1];
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-17.c b/gcc/testsuite/gcc.dg/builtin-object-size-17.c
index 0497bbf4505..09552a8a963 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-17.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-17.c
@@ -49,7 +49,9 @@ 
 typedef __SIZE_TYPE__ size_t;
 
 extern char ax[];
+#ifndef DYNAMIC_OBJECT_SIZE
 char ax2[];               /* { dg-warning "assumed to have one element" } */
+#endif
 
 extern char a0[0];
 static char a1[1];
diff --git a/gcc/tree-object-size.c b/gcc/tree-object-size.c
index e48120559d3..983df24719e 100644
--- a/gcc/tree-object-size.c
+++ b/gcc/tree-object-size.c
@@ -34,6 +34,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "tree-cfg.h"
 #include "stringpool.h"
 #include "attribs.h"
+#include "builtins.h"
 
 struct object_size_info
 {
@@ -46,7 +47,8 @@  enum
 {
   OST_SUBOBJECT = 1,
   OST_MINIMUM = 2,
-  OST_END = 4,
+  OST_DYNAMIC = 4,
+  OST_END = 8,
 };
 
 #define OST_TREE_CODE(_ost) ((_ost) & OST_MINIMUM ? MIN_EXPR : MAX_EXPR)
@@ -371,7 +373,8 @@  addr_object_size (struct object_size_info *osi, const_tree ptr,
 	  || TREE_CODE (TREE_OPERAND (pt_var, 0)) != SSA_NAME)
 	{
 	  compute_builtin_object_size (TREE_OPERAND (pt_var, 0),
-				       object_size_type & ~OST_SUBOBJECT, &sz);
+				       object_size_type & OST_MINIMUM, &sz,
+				       object_size_type & OST_DYNAMIC);
 	}
       else
 	{
@@ -835,9 +838,10 @@  resolve_dependency_loops (struct object_size_info *osi)
 
 bool
 compute_builtin_object_size (tree ptr, int object_size_type,
-			     tree *psize)
+			     tree *psize, bool dynamic)
 {
   gcc_assert (object_size_type >= 0 && object_size_type < OST_END);
+  object_size_type |= dynamic ? OST_DYNAMIC : 0;
 
   /* Set to unknown and overwrite just before returning if the size
      could be determined.  */
@@ -871,8 +875,10 @@  compute_builtin_object_size (tree ptr, int object_size_type,
 	      ptr = gimple_assign_rhs1 (def);
 
 	      if (tree_fits_shwi_p (offset)
-		  && compute_builtin_object_size (ptr, object_size_type,
-						  psize))
+		  && compute_builtin_object_size (ptr,
+						  (object_size_type
+						   & ~OST_DYNAMIC),
+						  psize, dynamic))
 		{
 		  /* Return zero when the offset is out of bounds.  */
 		  *psize = size_for_offset (*psize, offset);
@@ -893,8 +899,9 @@  compute_builtin_object_size (tree ptr, int object_size_type,
       object_sizes_grow (object_size_type);
       if (dump_file)
 	{
-	  fprintf (dump_file, "Computing %s %sobject size for ",
+	  fprintf (dump_file, "Computing %s %s%sobject size for ",
 		   (object_size_type & OST_MINIMUM) ? "minimum" : "maximum",
+		   dynamic ? "dynamic " : "",
 		   (object_size_type & OST_SUBOBJECT) ? "sub" : "");
 	  print_generic_expr (dump_file, ptr, dump_flags);
 	  fprintf (dump_file, ":\n");
@@ -917,9 +924,10 @@  compute_builtin_object_size (tree ptr, int object_size_type,
 		print_generic_expr (dump_file, ssa_name (i),
 				    dump_flags);
 		fprintf (dump_file,
-			 ": %s %sobject size ",
+			 ": %s %s%sobject size ",
 			 ((object_size_type & OST_MINIMUM) ? "minimum"
 			  : "maximum"),
+			 dynamic ? "dynamic " : "",
 			 (object_size_type & OST_SUBOBJECT) ? "sub" : "");
 		print_generic_expr (dump_file, object_sizes_get (&osi, i),
 				    dump_flags);
@@ -1310,8 +1318,80 @@  do_valueize (tree t)
   return t;
 }
 
+/* Process a __builtin_object_size or __builtin_dynamic_object_size call in
+   CALL early before any object information is lost due to optimization.
+   Insert a MIN or MAX expression of the result and __builtin_object_size at I
+   so that it may be processed in the second pass.  */
+
+static void
+early_object_sizes_execute_one (gimple_stmt_iterator *i, gimple *call)
+{
+  tree ost = gimple_call_arg (call, 1);
+  tree lhs = gimple_call_lhs (call);
+  gcc_assert (lhs != NULL_TREE);
+
+  if (tree_fits_uhwi_p (ost))
+    {
+      unsigned HOST_WIDE_INT object_size_type = tree_to_uhwi (ost);
+      tree ptr = gimple_call_arg (call, 0);
+      if ((object_size_type == 1 || object_size_type == 3)
+	  && (TREE_CODE (ptr) == ADDR_EXPR || TREE_CODE (ptr) == SSA_NAME))
+	{
+	  tree type = TREE_TYPE (lhs);
+	  tree bytes;
+	  if (compute_builtin_object_size (ptr, object_size_type, &bytes))
+	    {
+	      tree tem = make_ssa_name (type);
+	      gimple_call_set_lhs (call, tem);
+	      enum tree_code code
+		= object_size_type & OST_MINIMUM ? MAX_EXPR : MIN_EXPR;
+	      tree cst = fold_convert (type, bytes);
+	      gimple *g = gimple_build_assign (lhs, code, tem, cst);
+	      gsi_insert_after (i, g, GSI_NEW_STMT);
+	      update_stmt (call);
+	    }
+	}
+    }
+}
+
+/* Attempt to fold one __builtin_dynamic_object_size call in CALL into an
+   expression and insert it at I.  Return true if it succeeds.  */
+
+static bool
+dynamic_object_sizes_execute_one (gimple_stmt_iterator *i, gimple *call)
+{
+  unsigned numargs = gimple_call_num_args (call);
+  tree *args = XALLOCAVEC (tree, numargs);
+  args[0] = gimple_call_arg (call, 0);
+  args[1] = gimple_call_arg (call, 1);
+
+  location_t loc = EXPR_LOC_OR_LOC (args[0], input_location);
+  tree result_type = gimple_call_return_type (as_a <gcall *> (call));
+  tree result = fold_builtin_call_array (loc, result_type,
+					 gimple_call_fn (call), numargs, args);
+
+  if (result)
+    {
+      /* fold_builtin_call_array may wrap the result inside a
+	 NOP_EXPR.  */
+      STRIP_NOPS (result);
+      gimplify_and_update_call_from_tree (i, result);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "Simplified (dynamic)\n  ");
+	  print_gimple_stmt (dump_file, call, 0, dump_flags);
+	  fprintf (dump_file, " to ");
+	  print_generic_expr (dump_file, result);
+	  fprintf (dump_file, "\n");
+	}
+      return true;
+    }
+  return false;
+}
+
 static unsigned int
-object_sizes_execute (function *fun, bool insert_min_max_p)
+object_sizes_execute (function *fun, bool early)
 {
   basic_block bb;
   FOR_EACH_BB_FN (bb, fun)
@@ -1320,8 +1400,12 @@  object_sizes_execute (function *fun, bool insert_min_max_p)
       for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
 	{
 	  tree result;
+	  bool dynamic = false;
+
 	  gimple *call = gsi_stmt (i);
-	  if (!gimple_call_builtin_p (call, BUILT_IN_OBJECT_SIZE))
+	  if (gimple_call_builtin_p (call, BUILT_IN_DYNAMIC_OBJECT_SIZE))
+	    dynamic = true;
+	  else if (!gimple_call_builtin_p (call, BUILT_IN_OBJECT_SIZE))
 	    continue;
 
 	  tree lhs = gimple_call_lhs (call);
@@ -1330,41 +1414,39 @@  object_sizes_execute (function *fun, bool insert_min_max_p)
 
 	  init_object_sizes ();
 
-	  /* If insert_min_max_p, only attempt to fold
+	  /* If early, only attempt to fold
 	     __builtin_object_size (x, 1) and __builtin_object_size (x, 3),
 	     and rather than folding the builtin to the constant if any,
 	     create a MIN_EXPR or MAX_EXPR of the __builtin_object_size
 	     call result and the computed constant.  */
-	  if (insert_min_max_p)
+	  if (early)
 	    {
-	      tree ost = gimple_call_arg (call, 1);
-	      if (tree_fits_uhwi_p (ost))
+	      early_object_sizes_execute_one (&i, call);
+	      continue;
+	    }
+
+	  if (dynamic)
+	    {
+	      bool done = dynamic_object_sizes_execute_one (&i, call);
+	      if (done || early)
+		continue;
+	      else
 		{
-		  unsigned HOST_WIDE_INT object_size_type = tree_to_uhwi (ost);
-		  tree ptr = gimple_call_arg (call, 0);
-		  if ((object_size_type & OST_SUBOBJECT)
-		      && (TREE_CODE (ptr) == ADDR_EXPR
-			  || TREE_CODE (ptr) == SSA_NAME))
+		  /* If we could not find a suitable size expression, lower to
+		     __builtin_object_size so that we may at least get a
+		     constant lower or higher estimate.  */
+		  tree bosfn = builtin_decl_implicit (BUILT_IN_OBJECT_SIZE);
+		  gimple_call_set_fndecl (call, bosfn);
+		  update_stmt (call);
+
+		  if (dump_file && (dump_flags & TDF_DETAILS))
 		    {
-		      tree type = TREE_TYPE (lhs);
-		      tree bytes;
-		      if (compute_builtin_object_size (ptr, object_size_type,
-						       &bytes))
-			{
-			  tree tem = make_ssa_name (type);
-			  gimple_call_set_lhs (call, tem);
-			  enum tree_code code
-			    = (object_size_type & OST_MINIMUM
-			       ? MAX_EXPR : MIN_EXPR);
-			  tree cst = fold_convert (type, bytes);
-			  gimple *g
-			    = gimple_build_assign (lhs, code, tem, cst);
-			  gsi_insert_after (&i, g, GSI_NEW_STMT);
-			  update_stmt (call);
-			}
+		      print_generic_expr (dump_file, gimple_call_arg (call, 0),
+					  dump_flags);
+		      fprintf (dump_file,
+			       ": Retrying as __builtin_object_size\n");
 		    }
 		}
-	      continue;
 	    }
 
 	  result = gimple_fold_stmt_to_constant (call, do_valueize);
diff --git a/gcc/tree-object-size.h b/gcc/tree-object-size.h
index b2d6a58324c..edc7b573cc5 100644
--- a/gcc/tree-object-size.h
+++ b/gcc/tree-object-size.h
@@ -22,7 +22,8 @@  along with GCC; see the file COPYING3.  If not see
 
 extern void init_object_sizes (void);
 extern void fini_object_sizes (void);
-extern bool compute_builtin_object_size (tree, int, tree *);
+extern bool compute_builtin_object_size (tree, int, tree *,
+					 bool dynamic = false);
 extern tree decl_init_size (tree, bool);
 
 #endif  // GCC_TREE_OBJECT_SIZE_H