Chapter 8 Machine Instructions

1
Chapter 8 Machine Instructions

• These are lecture notes to accompany the book
  SPARC Architecture, Assembly Language
  Programming, and C,
• by Richard P. Paul, 2nd edition, 2000.
• By Michael Weeks

2
Decoding Instructions

• SPARC Instructions are 32 bits long
• Bits lt3130gt specify the op field
• These first 2 bits indicate how the other bits
  should be handled.

op
31 30 29


0
3
Decoding Instructions

• Instructions are classified according to op

op
31 30 29


0
op Instruction class 00 Branch instructions 01
Call instructions 10 Format Three
instructions 11 Format Three instructions
4
Format 1 Instructions

• Call instruction
• The displacement must be word aligned
• Address is calculated by right shifting
  displacement 2 positions

01
30 bit displacement
31 30 29


0
5
Format 2 Instructions

• branch

0 0 a cond op2 22 bit immediate
31 30 29 28 25 24
22 21

0

• sethi

0 0 rd 1 0 0 22 bit
immediate
31 30 29 25 24
22 21

0
6
Branch Instructions

• The branch is (or is not) taken based on the
  cond (condition) field.
• op2 010 means integer condition code

cond branch type 1000 always 1001 if not equal to
zero 1010 if greater than zero 1011 if greater
than or equal to zero 1100 if greater,
unsigned 1101 if carry is clear 1110 if
positive 1111 if overflow is clear
cond branch type 0000 never 0001 if equal to
zero 0010 if less than or equal to zero 0011 if
less than zero 0100 if less or equal,
unsigned 0101 if carry set 0110 if
negative 0111 if overflow is set
7
Format 3 Instructions

• 2 source registers

1 x rd op3 rs1 0
rs2
31 30 29 25 24
19 18 14 13
12 5 4
0

• Immediate constant

1 x rd op3 rs1 1
signed 13-bit
31 30 29 25 24
19 18 14 13
12 5 4
0
8
Format Three Instructions

• Not all possible bits patterns are used
• op 10

op3 Instruction 000000 add 000001 and 000010 or 00
0011 xor 000100 sub 000101 andn 000110 orn 000111
xnor 001000 addx
op3 Instruction 111000 jumpl 111001 rett 111010 ti
cc 111011 iflush 111100 save 111101 restore 111110
ltunusedgt 111111 ltunusedgt
See page 235 for a complete list
9
Format Three Instructions

• Not all possible bits patterns are used
• op 11

op3 Instruction 000000 ld 000001 ldub 000010 lduh
000011 ldd 000100 st 000101 stb 000110 sth 000111
std 001000 ltunusedgt
See page 236 for a complete list
10
Example

• Decode the following commands

• 0x9de3bfa0
• 0xd007bfec
• 0x92102004
• 0x90020009
• 0xd027bfec
• 0x81c7e008
• 0x81e80000

save sp, -96, sp
ld fp-20, o0
mov 4, o1
add o0, o1, o0
st o0, fp-20
ret
restore