Integer Execution Unit (Ieu) Instructions - Sun Microsystems UltraSPARC-I User Manual

UltraSPARC User's Manual

17.5 Integer Execution Unit (IEU) Instructions

IEU instructions can be dispatched only if they are in the first three instruction
slots. A maximum of two IEU instructions can be executed in one cycle. There are
two IEU pipelines: IEU
some IEU instructions can be dispatched only to a particular pipeline. The fol-
lowing instructions can dispatched to either IEU pipeline:
, , ,
ORN SUB XOR
with older IEU
0
The IEU data path has dedicated hardware for shift instructions:
0
. Two shift instructions cannot be grouped together. Shift instructions can
SRA{X}
be grouped with older IEU
with older non-specific IEU instructions. For example:
ADD i1, i2, i6
SLL i6, 2, i8
The IEU datapath has dedicated hardware for the condition-code-setting instruc-
1
tions: (
TADDcc{TV}
, ),
XORcc XNORcc
MP{LE,NE,GT,EQ}{16,32}
store, or floating-point instructions respectively), since they must access the inte-
ger register file. Two instructions requiring the use of IEU
gether; for example, only one instruction that sets the condition codes can be
dispatched per cycle. An IEU
structions and non-specific IEU instructions.
Note: For UltraSPARC-II, a valid control transfer instruction (CTI) that was
fetched from the end of a cache line is not dispatched until its delay slot also has
been fetched.
17.5.1 Multi-Cycle IEU Instructions
Some integer instructions execute for several cycles and sometimes prevent the
dispatch of subsequent instructions until they complete.
inserts one bubble after it is dispatched.
MULScc
inserts 36 bubbles,
SDIV{cc}
bubbles after they are dispatched.
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and IEU . The two data paths are slightly different, and
0 1
and . These instructions can be grouped together or
XNOR SETHI
or IEU specific instructions.
1
specific instructions, but they cannot be grouped
1
G E C N N
1 2
G E C N
1
, , ,
TSUBcc{TV} ADDcc ANDcc
and . ,
EDGE ARRAY CALL
also require the IEU
instruction can be grouped with older shift in-
1
inserts 37 bubbles, and
UDIV{cc}
,
ADD AND
SLL{X}
N W
3
N N W
2 3
, , ,
ANDNcc ORcc ORNcc
, , and
JMPL BPr PST FC-
data path (besides counting as CTI,
1
cannot be grouped to-
1
{U,S}DIVX
, , ,
ANDN OR
, .
SRL{X}
, ,
SUBcc
inserts 68