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>

1 files changed, 5 insertions, 5 deletions

diff --git a/src/base/circular_queue.hh b/src/base/circular_queue.hh
index f368ed0d1..da3da8b28 100644
--- a/src/base/circular_queue.hh
+++ b/src/base/circular_queue.hh
@@ -323,12 +323,12 @@ class CircularQueue : private std::vector<T>
             assert(_cq);
 
             /* C does not do euclidean division, so we have to adjust */
-            if (t >= 0)
+            if (t >= 0) {
                 _round += (-t + _idx) / _cq->capacity();
-            else
-                _round += (-t + _idx - _cq->capacity() + 1) / _cq->capacity();
-
-            _idx = _cq->moduloSub(_idx, t);
+                _idx = _cq->moduloSub(_idx, t);
+            } else {
+                *this += -t;
+            }
             return *this;
         }