[PATCH] tree-optimization/108522 Use component_ref_field_offset

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

Instead of using TREE_OPERAND (expr, 2) directly, use
component_ref_field_offset instead, which does scaling for us.  The
function also substitutes PLACEHOLDER_EXPRs, which is probably what we
want anyway but I'm not sure if it's relevant for tree-object-size.

gcc/ChangeLog:

	PR tree-optimization/108522
	* tree-object-size.cc (compute_object_offset): Make EXPR
	argument non-const.  Call component_ref_field_offset.

gcc/testsuite/ChangeLog:

	PR tree-optimization/108522
	* gcc.dg/builtin-dynamic-object-size-0.c (DEFSTRUCT): New
	macro.
	(test_dynarray_struct_member_b, test_dynarray_struct_member_c,
	test_dynarray_struct_member_d,
	test_dynarray_struct_member_subobj_b,
	test_dynarray_struct_member_subobj_c,
	test_dynarray_struct_member_subobj_d): New tests.
	(main): Call them.

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
---
Testing:
- Tested i686 to confirm that there are no new regressions
- Tested x86_64 bootstrap and confirmed that there are no new
  regressions
- ubsan config bootstrap in progress

 .../gcc.dg/builtin-dynamic-object-size-0.c    | 81 +++++++++++++++++--
 gcc/tree-object-size.cc                       |  7 +-
 2 files changed, 77 insertions(+), 11 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
index 569c0a87722..76079d8702e 100644
--- a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
@@ -315,19 +315,70 @@ test_dynarray_struct_subobj2 (size_t sz, size_t off, size_t *objsz)
 }
 
 /* See pr #108522.  */
+
+#define DEFSTRUCT(_s, _n) \
+  struct DS								      \
+    {									      \
+      char a[_n];							      \
+      unsigned long long b;						      \
+      int c;								      \
+      char d[2 * _n];							      \
+    } _s
+
 size_t
 __attribute__ ((noinline))
-test_dynarray_struct_member (size_t sz)
+test_dynarray_struct_member_b (size_t sz)
 {
-  struct
-    {
-      char a[sz];
-      char b;
-    } s;
+  DEFSTRUCT (s, sz);
 
   return __builtin_dynamic_object_size (&s.b, 0);
 }
 
+size_t
+__attribute__ ((noinline))
+test_dynarray_struct_member_c (size_t sz)
+{
+  DEFSTRUCT (s, sz);
+
+  return __builtin_dynamic_object_size (&s.c, 0);
+}
+
+size_t
+__attribute__ ((noinline))
+test_dynarray_struct_member_d (size_t sz, size_t offset)
+{
+  DEFSTRUCT (s, sz);
+
+  return __builtin_dynamic_object_size (&s.d[offset], 0);
+}
+
+size_t
+__attribute__ ((noinline))
+test_dynarray_struct_member_subobj_b (size_t sz)
+{
+  DEFSTRUCT (s, sz);
+
+  return __builtin_dynamic_object_size (&s.b, 1);
+}
+
+size_t
+__attribute__ ((noinline))
+test_dynarray_struct_member_subobj_c (size_t sz)
+{
+  DEFSTRUCT (s, sz);
+
+  return __builtin_dynamic_object_size (&s.c, 1);
+}
+
+size_t
+__attribute__ ((noinline))
+test_dynarray_struct_member_subobj_d (size_t sz, size_t offset)
+{
+  DEFSTRUCT (s, sz);
+
+  return __builtin_dynamic_object_size (&s.d[offset], 1);
+}
+
 size_t
 __attribute__ ((noinline))
 test_substring (size_t sz, size_t off)
@@ -633,7 +684,23 @@ main (int argc, char **argv)
   if (test_dynarray_struct_subobj2 (42, 4, &objsz)
     != objsz - 4 - sizeof (long) - sizeof (int))
     FAIL ();
-  if (test_dynarray_struct_member (42) != sizeof (char))
+  DEFSTRUCT(ds, 64);
+  const size_t n = sizeof (ds.a);
+  if (test_dynarray_struct_member_b (n)
+      != sizeof (ds) - __builtin_offsetof (struct DS, b))
+    FAIL ();
+  if (test_dynarray_struct_member_c (n)
+      != sizeof (ds) - __builtin_offsetof (struct DS, c))
+    FAIL ();
+  if (test_dynarray_struct_member_d (n, 0)
+      != sizeof (ds) - __builtin_offsetof (struct DS, d))
+    FAIL ();
+  if (test_dynarray_struct_member_subobj_b (n) != sizeof (ds.b))
+    FAIL ();
+  if (test_dynarray_struct_member_subobj_c (n) != sizeof (ds.c))
+    FAIL ();
+  if (test_dynarray_struct_member_subobj_d (n, n - 2)
+      != sizeof (ds) - __builtin_offsetof (struct DS, d) - n + 2)
     FAIL ();
   if (test_substring_ptrplus (128, 4) != (128 - 4) * sizeof (int))
     FAIL ();
diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc
index de93ffad9c9..9a936a91983 100644
--- a/gcc/tree-object-size.cc
+++ b/gcc/tree-object-size.cc
@@ -56,7 +56,7 @@ struct GTY(()) object_size
   tree wholesize;
 };
 
-static tree compute_object_offset (const_tree, const_tree);
+static tree compute_object_offset (tree, const_tree);
 static bool addr_object_size (struct object_size_info *,
 			      const_tree, int, tree *, tree *t = NULL);
 static tree alloc_object_size (const gcall *, int);
@@ -396,7 +396,7 @@ size_for_offset (tree sz, tree offset, tree wholesize = NULL_TREE)
    if unknown.  */
 
 static tree
-compute_object_offset (const_tree expr, const_tree var)
+compute_object_offset (tree expr, const_tree var)
 {
   enum tree_code code = PLUS_EXPR;
   tree base, off, t;
@@ -413,8 +413,7 @@ compute_object_offset (const_tree expr, const_tree var)
 
       t = TREE_OPERAND (expr, 1);
       off = size_binop (PLUS_EXPR,
-			(TREE_OPERAND (expr, 2) ? TREE_OPERAND (expr, 2)
-			 : DECL_FIELD_OFFSET (t)),
+			component_ref_field_offset (expr),
 			size_int (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (t))
 				  / BITS_PER_UNIT));
       break;
-- 
2.38.1