Xilinx MicroBlaze Reference Manual page 209

frsub
Reverse Floating Point Arithmetic Subtraction
frsub
0 1 0 1 1 0
0 6
Description
The floating point value in rA is subtracted from the floating point value in rB and the result is
placed into register rD.
Pseudocode
if isDnz(rA) or isDnz(rB) then
←
(rD)
FSR[DO]
ESR[EC]
else if (isSigNaN(rA) or isSigNaN(rB) or
(isPosInfinite(rA) and isPosInfinite(rB)) or
(isNegInfinite(rA) and isNegInfinite(rB))) then
←
(rD)
FSR[IO]
ESR[EC]
else if isQuietNaN(rA) or isQuietNaN(rB) then
←
(rD)
else if isDnz((rB)-(rA)) then
←
(rD)
FSR[UF]
ESR[EC]
else if isNaN((rB)-(rA)) then
←
(rD)
FSR[OF]
ESR[EC]
else
←
(rD)
Registers Altered
• rD, unless an FP exception is generated, in which case the register is unchanged
• ESR[EC], if an FP exception is generated
• FSR[IO,UF,OF,DO]
Latency
• 4 cycles with
• 6 cycles with
Note
This instruction is only available when the MicroBlaze parameter C_USE_FPU is greater than 0.
MicroBlaze Processor Reference Guide
UG984 (v2016.2) June 8, 2016
UG984 (v2016.1) April 6, 2016
rD, rA, rB Reverse subtract
rD rA
11
0xFFC00000
←
1
←
00110
0xFFC00000
←
1
←
00110
0xFFC00000
signZero((rB)-(rA))
←
1
←
00110
signInfinite((rB)-(rA))
←
1
←
00110
(rB) - (rA)
C_AREA_OPTIMIZED
C_AREA_OPTIMIZED
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Chapter 5: MicroBlaze Instruction Set Architecture
rB 0 0 0 1 0 0 0 0 0 0 0
16 21
=0
=1
31
209
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