[Bug sanitizer/87837] [8/9 Regression] -O2 -fsanitize=signed-integer-overflow misses overflows on x86-64

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87837

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 44939
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44939&action=edit
gcc9-pr87837.patch

Untested fix for this issue.  Note, we should go through all of match.pd and
for each TYPE_OVERFLOW_UNDEFINED not accompanied with !TYPE_OVERFLOW_SANITIZED
try to think if that might cause some missed cases, construct testcases and fix
if needed.  Don't have spare cycles for that right now though.