
3-18
G2 PowerPC Core Reference Manual
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MOTOROLA
Instruction Set Summary
3.2.4.2.5
Floating-Point Status and Control Register Instructions
Every FPSCR instruction appears to synchronize the effects of all floating-point
instructions executed by a given processor. Executing an FPSCR instruction ensures that
all floating-point instructions previously initiated by the given processor appear to have
completed before the FPSCR instruction is initiated and that no subsequent floating-point
instructions appear to be initiated by the given processor until the FPSCR instruction has
completed. The FPSCR instructions are listed in Table 3-12.
Implementation Note
—The architecture notes that, in some implementations, the Move
to FPSCR Fields (
mtfsf
x
) instruction may perform more slowly when only a portion of the
fields are updated as opposed to all of the fields. This is not the case in the G2 core.
3.2.4.2.6
Floating-Point Move Instructions
Floating-point move instructions copy data from one floating-point register to another. The
floating-point move instructions do not modify the FPSCR. The CR update option in these
instructions controls the placing of result status into CR1. Floating-point move instructions
are listed in Table 3-13.
Table 3-11. Floating-Point Compare Instructions
Name
Mnemonic
Operand Syntax
Floating Compare Ordered
fcmpo
crf
D
,fr
A
,fr
B
Floating Compare Unordered
fcmpu
crf
D
,fr
A
,fr
B
Table 3-12. Floating-Point Status and Control Register Instructions
Name
Mnemonic
Operand Syntax
Move from FPSCR
mffs
(
mffs.
)
fr
D
Move to Condition Register
from FPSCR
mcrfs
crf
D
,crf
S
Move to FPSCR Bit 0
mtfsb0
(
mtfsb0.
)
crb
D
Move to FPSCR Bit 1
mtfsb1
(
mtfsb1.
)
crb
D
Move to FPSCR Field Immediate
mtfsfi
(
mtfsfi.
)
crf
D
,
IMM
Move to FPSCR Fields
mtfsf
(
mtfsf.
)
FM
,fr
B
Table 3-13. Floating-Point Move Instructions
Name
Mnemonic
Operand Syntax
Floating Absolute Value
fabs
(
fabs.
)
fr
D
,fr
B
Floating Move Register
fmr
(
fmr.
)
fr
D
,fr
B
Floating Negate
fneg
(
fneg.
)
fr
D
,fr
B
Floating Negative Absolute Value
fnabs
(
fnabs.
)
fr
D
,fr
B
F
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n
.