SPARC Instruction Set

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SPARC Programming Model

• 24 window registers
• 8 global registers
• Control registers
• Multiply step
• PSR (status flags, etc.)
• Trap Base register
• Window Invalid Mask
• Two program counters (PC and nPC)

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SPARC Program
/ This program converts a temperature in
Celcius to Fahrenheit. George Wells - 30 May
2003 / offs 32 / Variables c and f
are stored in l0 and l1 / .global
main main mov 24, l0 !
Initialize c 24 mov 9, o0 ! 9
into o0 for multiplication mov l0,
o1 ! c into o1 for multiplication
call .mul ! Result in o0 nop
! Delay slot mov 5, o1
! 5 into o1 for division call .div
! Result in o0 nop
! Delay slot
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Example (cont.)
... add o0, offs, l1 ! f
result offs mov 1, g1 !
Trap dispatch ta 0 !
Trap to system
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Filling Delay Slots
mov 9, o0 ! 9 into o0 for
multiplication mov l0, o1 ! c
into o1 for multiplication call .mul
! Result in o0 nop !
Delay slot

• Not very efficient

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Modified Program
main mov 24, l0 ! Initialize c
24 mov 9, o0 ! 9 into o0 for
multiplication call .mul !
Result in o0 mov l0, o1 ! c into
o1 for multiplication call .div
! Result in o0 mov 5, o1 ! 5
into o1 for division ...
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3. Control Transfer Instructions

• Branching
• Unconditional ba bn
• Conditional bicc
• icc Integer Condition Codes

• Condition flags are set explicitly by arithmetic
  and logical operations
• E.g. addcc

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Delayed Control Transfer

• Increases the efficiency of pipelining

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Example
/ This program converts temperatures between 10
and 20 in Celcius to Fahrenheit. George
Wells - 30 May 2003 / offs 32 /
Variables c and f are stored in l0 and l1 /
.global main main mov 10, l0
! Initialize c 10 loop mov
9, o0 ! 9 into o0 for .mul
call .mul ! Result in o0
mov l0, o1 ! c into o1 for .mul
call .div ! Result in o0
mov 5, o1 ! 5 into o1 for .div
. . .
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Example (cont.)
. . . add o0, offs, l1 ! f
result offs add l0, 1, l0
! c cmp l0, 21 ! c lt 21
? bl loop nop
! Delay slot mov 1, g1
! Trap dispatch ta 0
! Trap to system
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Annulled Branches

• Delay slot instruction is ignored
• Conditional if branch is not taken
• Unconditional always annulled

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An Annulled Branch

• Java/C Code

while (a lt 17) a a b
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Optimised Assembler
! Assumes a is in l0 and b is in l1 b test
! See if loop should execute nop ! Delay
slot loop test cmp l0, 17 ! a lt 17
ble,a loop ! If so branch back to start add
l0, l1, l0 ! a a b
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4. Logical and Arithmetic Operations

• Logical Operators
• and or xor
• xnor andn orn
• cc to set the condition codes
• Shift Operators
• sra srl sll

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Arithmetic Operators

• Only addition and subtraction
• addxcc
• subxcc
• x with carry
• cc to set the flags

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Multiplication

• Long multiplication is supported by the multiply
  step instruction
• mulscc

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Division

• Use the standard routines
• .div .rem
• .udiv .urem

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