ALT Linux
valgrind package

  1. Bug #852760
  2. Comment #2

Comment 2 for bug 852760

Revision history for this message
In , Joost-vandevondele (joost-vandevondele) wrote :

This bug report relates to two (closed invalid) bug reports in gcc bugzilla.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47522
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44183

PR47522 includes a runable example in the first comment.

the issue appears to be that vectorization can result in code that loads elements beyond the last element of an allocated array. However, these loads will only happen for unaligned data, where access to the last+1 element can't trigger a page fault or other side effects (according to my interpretation of comments by gcc developers) and are never used. As such, this is considered valid.

Since this kind of code will be produced increasingly by gcc, especially for numerical codes (whenever vectorization triggers, essentially) it would be great to have this somehow dealt with in valgrind.