
Sun Microelectronics
287
17. Grouping Rules and Stalls
17.6 Control Transfer Instructions
One Control Transfer Instruction (CTI) can be dispatched per group. The follow-
ing control transfer instructions are not single group instructions:
CALL
,
BPcc
,
Bicc
,
FB(P)fcc
,
BPr
, and
JMPL
.
CALL
and
JMPL
are always dispatched as the oldest
instruction in the group; that is, a group break is forced before dispatching these
instructions.
DONE
,
RETRY
, and the second instruction of a delayed control transfer instruction
(DCTI) couple flush the pipe when they reach the W Stage, effectively inserting
nine bubbles into the pipe. The pipeline is flushed even if the second DCTI is an-
nulled.
17.6.1 Control Transfer Dependencies
UltraSPARC can group instructions following a control transfer with the control
transfer instruction. Instructions following the delay slot come from the predicted
instruction stream. For example, if a branch is predicted taken:
If the branch is predicted not taken:
FCMPLE16
→
i6
G
E
C
N
1
N
2
N
3
W
FMOVr
i5
G
E
C
N
1
N
2
N
3
W
setcc
G
E
C
N
1
N
2
N
3
W
BPcc
G
E
C
N
1
N
2
N
3
W
FADD (delay slot)
G
E
C
N
1
N
2
N
3
W
FMUL
(branch target)
G
E
C
N
1
N
2
N
3
W
setcc
G
E
C
N
1
N
2
N
3
W
BPcc
G
E
C
N
1
N
2
N
3
W
FADD (delay slot)
G
E
C
N
1
N
2
N
3
W
FDIV
(sequential)
G
E
C
N
1
N
2
N
3
W
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