Transcript Floating-Point Instructions: Conversion

QuadCore Team – DLX ISA
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David Bild
Greg Bok
Jake Czyz
Brandon Keao
Floating-Point Instructions
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There are three categories for the DLX
floating-point instructions:
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Arithmetic
Conversion
Set-on-comparison
All operation occur in the floating-point
registers and are in the R-type format.
DLX ISA
Floating-Point Instructions: Arithmetic
Brandon Keao
Floating-Point Instructions: Arithmetic
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These intructions preform arithmetic
operations on two floating-point registers
Always R-format
There are 2 categories of floating-point
arithmetic instructions:
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Single-precision
Double-precision
Floating-Point Instructions: Arithmetic
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SP operations interpret the values in the two
registers as SP FP values
The result is rounded to a SP value and
stored in a FP register
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ADDF- Adds two SP values
SUBF - Subtracts two SP values
MULTF - Multiplies two SP values
DIVF - Divides two SP values
Floating-Point Instructions: Arithmetic
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DP operations interpret the values of two
even/odd pairs of FP registers as DP FP
values.
The result if rounded to a DP value and
stored in an even/odd pair of FP registers.
 ADDD - Adds two DP values
 SUBD - Subtracts two DP values
 MULTD - Multiplies two DP values
 DIVD - Divides two DP values
DLX ISA
Floating-Point Instructions: Conversion
And
Special Instructions
Greg Bok
Floating-Point Instructions: Conversion
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Sometimes need to convert between
precisions or integer/floating-point
The DLX ISA includes 6 such instructions
R-format
Double-precision FP register operands
must be even-numbered FP registers
32-bit integers used
Floating-Point Instructions: Conversion
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CVT2DF: double-precision to single-precision
CVTD2I: double-precision to integer
CVTF2D: single-precision to double-precision
CVTF2I: single-precision to integer
CVTI2D: integer to double-precision
CVTI2F: integer to single-precision
Special Instructions: TRAP
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J-type, unconditional branch
26-bit name field zero-extended to 32bits to obtain target address
Moves PC + 8 to IAR (interrupt address
register)
Special Instructions: RFE
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Return From Exception
J-type, unconditional
Returns to code that was executing
before TRAP instruction
Moves value in IAR register to PC
Special Instructions: NOP
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R-type
Performs no operation -- hardware state
is unaffected
Typically used to fill branch delay slots
when no useful instruction will work
DLX ISA
Floating-Point Instructions:
Set-on-Comparison
David Bild
Floating-Point Instructions: SetOn-Comparison
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Compares two floating point numbers
(SP or DP)
Sets FPSR (Floating Point Status
Register) to ‘1’ if comparison is true, ‘0’
if false
6 comparisons are provided: <, >, =. <=,
>=, ~=
DLX ISA
Load & Store Instructions
Jake Czyz
Load and Store Instructions
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For loading/storing data from/to memory
Handle data of size:
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Byte
Halfword
Word
Double (for floating point only)
Load and Store Instructions
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Byte and Halfword instructions always
load/store the least significant byte or
halfword, respectively.
Loads and Stores may be done with any
of the general purpose registers, except
that loading R0 has no effect (it always
stores the value 0x00000000).
Load and Store Instructions
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All are I-Type
Bit #'s
Width
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0
5
6
10
11
15
16
31
Opcode
rs1
rd
Immediate
6
5
5
16
Data always moved between memory and
the register(s) specified by rd
Load and Store Instructions
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Load/Store Address Calculations:
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Load
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lw rd rs1 imm
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rd = Mem(Sign_Extend(imm) + rs1)
Store
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sw rd rs1 imm
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Mem(Sign_Extend(imm) + rs1) = rd
Load Instructions
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LB
LBU
LH
LHU
LW
LF
LD
Loads a byte (w/ sign ext.)
Loads a byte (w/ zero ext.)
Loads a halfword (w/ sign ext.)
Loads a halfword (w/ zero ext.)
Loads a word
Loads a single precision float
Loads a double precision float*
*to/from a pair of even/odd registers
Store Instructions
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SB
SH
SW
SF
SD
Stores a byte
Stores a halfword
Stores a word
Stores a single precision float
Stores a double precision float*
*to/from a pair of even/odd registers
Thank You