Avoid left shift of negative value in ipa-modref-tree.h
Jan Hubicka
hubicka@kam.mff.cuni.cz
Fri Nov 5 22:19:57 GMT 2021
Hi,
ubsan is complaining about left shift of negative value which is
undefined in c++11..c++17. Replaced by multiplication.
Bootstrapped/regtested x86_64-linux, comitted.
Honza
gcc/ChangeLog:
PR ipa/103082
* ipa-modref-tree.h (struct modref_access_node): Avoid left shift
of negative value
diff --git a/gcc/ipa-modref-tree.h b/gcc/ipa-modref-tree.h
index 9976e489697..bc428d193d2 100644
--- a/gcc/ipa-modref-tree.h
+++ b/gcc/ipa-modref-tree.h
@@ -116,8 +116,13 @@ struct GTY(()) modref_access_node
if (!known_le (parm_offset, a.parm_offset)
&& !range_info_useful_p ())
return false;
+ /* We allow negative aoffset_adj here in case
+ there is an useful range. This is because adding
+ a.offset may result in non-ngative offset again.
+ Ubsan fails on val << LOG_BITS_PER_UNIT where val
+ is negative. */
aoffset_adj = (a.parm_offset - parm_offset)
- << LOG2_BITS_PER_UNIT;
+ * BITS_PER_UNIT;
}
}
if (range_info_useful_p ())
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