[gcc r12-5649] tree-optimization/103456 - Record only successes from object_sizes_set

[Siddhesh Poyarekar <siddhesh@gcc.gnu.org>]

https://gcc.gnu.org/g:da9386f9a70ac494939650c0e0a0e4168a6f76d8

commit r12-5649-gda9386f9a70ac494939650c0e0a0e4168a6f76d8
Author: Siddhesh Poyarekar <siddhesh@gotplt.org>
Date:   Wed Dec 1 12:58:12 2021 +0530

    tree-optimization/103456 - Record only successes from object_sizes_set
    
    Avoid overwriting osi->changed if object_sizes_set does not update the
    size, so that a previous success in the same pass is not overwritten.
    This fixes the bootstrap-ubsan build config, which was failing due to
    incorrect object size.
    
    gcc/ChangeLog:
    
            PR tree-optimization/103456
            * tree-object-size.c (merge_object_sizes): Update osi->changed
            only if object_sizes_set succeeded.
    
    gcc/testsuite/ChangeLog:
    
            PR tree-optimization/103456
            * gcc.dg/ubsan/pr103456.c: New test.
    
    Co-authored-by: Martin Liška <mliska@suse.cz>
    Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>

Diff:
---
 gcc/testsuite/gcc.dg/ubsan/pr103456.c | 21 +++++++++++++++++++++
 gcc/tree-object-size.c                |  3 ++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/ubsan/pr103456.c b/gcc/testsuite/gcc.dg/ubsan/pr103456.c
new file mode 100644
index 00000000000..20322fbaab1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/pr103456.c
@@ -0,0 +1,21 @@
+/* PR tree-optimization/103456 */
+/* { dg-do compile } */
+/* { dg-options "-fsanitize=undefined -O -fdump-tree-objsz" } */
+
+static char *multilib_options = "m64/m32";
+
+void
+used_arg_t (void)
+{
+  char *q = multilib_options;
+  for (;;)
+    {
+      while (*q)
+	q++;
+      while (__builtin_strchr (q, '_') == 0)
+	while (*q)
+	  q++;
+    }
+}
+
+/* { dg-final { scan-tree-dump-not "maximum object size 0" "objsz1" } } */
diff --git a/gcc/tree-object-size.c b/gcc/tree-object-size.c
index 3780437ff91..b4881ef198f 100644
--- a/gcc/tree-object-size.c
+++ b/gcc/tree-object-size.c
@@ -854,7 +854,8 @@ merge_object_sizes (struct object_size_info *osi, tree dest, tree orig,
     orig_bytes = (offset > orig_bytes)
 		 ? HOST_WIDE_INT_0U : orig_bytes - offset;
 
-  osi->changed = object_sizes_set (osi, varno, orig_bytes);
+  if (object_sizes_set (osi, varno, orig_bytes))
+    osi->changed = true;
 
   return bitmap_bit_p (osi->reexamine, SSA_NAME_VERSION (orig));
 }