base: Fix CircularQueue's operator-= when negative subtraction

Using operator-= when the rhs is a negative value is equivalent
to using += on -rhs. This is fixing rounding in that scenario.

Change-Id: Ia22e51f81a6805d27fd6b2115d288bb23421d00f
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17528
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

base: Fix CircularQueue when diffing iterators

This patch is fixing CircularQueue iterators' subtraction, in particular
the behaviour when head and tail round multiple times.

Change-Id: Ie79ac8accd30a10cf039cf4def87675b01375d6b
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17188
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

base: Iterable CircularQueue implementation

The former implementation of CircleBuf is functional but a bit too
tailored to match a use-case. This patches introduces a new iterable
circular queue, which adds some more functionality so it can also be
used for the newer LSQ implementation, where iteration and iterators
are a very desirable feature.

Additional contributors: Gabor Dozsa.

Change-Id: I5cfb95c8abc1f5e566a114acdbf23fc52a38ce5e
Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13127
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>