[PATCH v2 1/4] tree-object-size: use size_for_offset in more cases

[Siddhesh Poyarekar]

When wholesize != size, there is a reasonable opportunity for static
object sizes also to be computed using size_for_offset, so use that.

gcc/ChangeLog:

        * tree-object-size.cc (plus_stmt_object_size): Call
        SIZE_FOR_OFFSET for some negative offset cases.
        * testsuite/gcc.dg/builtin-object-size-3.c (test9): Adjust test.
        * testsuite/gcc.dg/builtin-object-size-4.c (test8): Likewise.
---
 gcc/testsuite/gcc.dg/builtin-object-size-3.c | 6 +++---
 gcc/testsuite/gcc.dg/builtin-object-size-4.c | 6 +++---
 gcc/tree-object-size.cc                      | 2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-3.c 
b/gcc/testsuite/gcc.dg/builtin-object-size-3.c
index 3f58da3d500..ec2c62c9640 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-3.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-3.c
@@ -574,7 +574,7 @@ test9 (unsigned cond)
   if (__builtin_object_size (&p[-4], 2) != (cond ? 6 : 10))
     FAIL ();
 #else
-  if (__builtin_object_size (&p[-4], 2) != 0)
+  if (__builtin_object_size (&p[-4], 2) != 6)
     FAIL ();
 #endif
 
@@ -585,7 +585,7 @@ test9 (unsigned cond)
   if (__builtin_object_size (p, 2) != ((cond ? 2 : 6) + cond))
     FAIL ();
 #else
-  if (__builtin_object_size (p, 2) != 0)
+  if (__builtin_object_size (p, 2) != 2)
     FAIL ();
 #endif
 
@@ -598,7 +598,7 @@ test9 (unsigned cond)
       != sizeof (y) - __builtin_offsetof (struct A, c) - 8 + cond)
     FAIL ();
 #else
-  if (__builtin_object_size (p, 2) != 0)
+  if (__builtin_object_size (p, 2) != sizeof (y) - __builtin_offsetof (struct 
A, c) - 8)
     FAIL ();
 #endif
 }
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-4.c 
b/gcc/testsuite/gcc.dg/builtin-object-size-4.c
index b3eb36efb74..7bcd24c4150 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-4.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-4.c
@@ -482,7 +482,7 @@ test8 (unsigned cond)
   if (__builtin_object_size (&p[-4], 3) != (cond ? 6 : 10))
     FAIL ();
 #else
-  if (__builtin_object_size (&p[-4], 3) != 0)
+  if (__builtin_object_size (&p[-4], 3) != 6)
     FAIL ();
 #endif
 
@@ -493,7 +493,7 @@ test8 (unsigned cond)
   if (__builtin_object_size (p, 3) != ((cond ? 2 : 6) + cond))
     FAIL ();
 #else
-  if (__builtin_object_size (p, 3) != 0)
+  if (__builtin_object_size (p, 3) != 2)
     FAIL ();
 #endif
 
@@ -505,7 +505,7 @@ test8 (unsigned cond)
   if (__builtin_object_size (p, 3) != sizeof (y.c) - 8 + cond)
     FAIL ();
 #else
-  if (__builtin_object_size (p, 3) != 0)
+  if (__builtin_object_size (p, 3) != sizeof (y.c) - 8)
     FAIL ();
 #endif
 }
diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc
index 6544730e153..f8fae0cbc82 100644
--- a/gcc/tree-object-size.cc
+++ b/gcc/tree-object-size.cc
@@ -1527,7 +1527,7 @@ plus_stmt_object_size (struct object_size_info *osi, tree 
var, gimple *stmt)
       if (size_unknown_p (bytes, 0))
        ;
       else if ((object_size_type & OST_DYNAMIC)
-              || compare_tree_int (op1, offset_limit) <= 0)
+              || bytes != wholesize || compare_tree_int (op1, offset_limit) <= 
0)
        bytes = size_for_offset (bytes, op1, wholesize);
       /* In the static case, with a negative offset, the best estimate for
         minimum size is size_unknown but for maximum size, the wholesize is a
-- 
2.45.1