[Bug lto/78140] [7 Regression] libxul -flto uses 1GB more memory than gcc-6

["jamborm at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78140

--- Comment #28 from Martin Jambor <jamborm at gcc dot gnu.org> ---
(In reply to Martin Jambor from comment #27)
> Unfortunately, something else has added a further gigabyte to WPA of
> FF in the last week:

So this fortunately turnout to be a mistake in measurement, I was
comparing a --enable-gather-detailed-mem-stats build with a normal
one.  The correct values are:

  | compiler            | wpa mem (KB) | wpa mem (GB) |
  |---------------------+--------------+--------------|
  | gcc 6 branch        |      4046451 |         3.86 |
  | trunk rev. 245382   |      5468227 |         5.21 |
  | patched rev. 245382 |      4255799 |         4.06 |
  | trunk rev. 245595   |      5452515 |         5.20 |
  | patched rev. 245595 |      4240379 |         4.04 |

Thus, the patch avoids most of the reported increase in memory use.