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
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

2. Decoding Instructions
SPARC Instructions are 32 bits long
Bits <31:30> specify the “op” field
These first 2 bits indicate how the other bits should be handled. op
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

3. Decoding Instructions
Instructions are classified according to “op” op
op Instruction class
00 Branch instructions
01 Call instructions
10 Format Three instructions
11 Format Three instructions
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

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
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

5. Format 2 Instructions branch sethi 0 0 a cond op2 22 bit immediate
sethi
rd bit immediate
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

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
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
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
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

7. Format 3 Instructions 2 source registers Immediate constant
1 x rd op rs rs2
Immediate constant
1 x rd op rs signed 13-bit #
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

8. Format Three Instructions
Not all possible bits patterns are used
op = 10
op3 Instruction
add
and or
xor
sub
andn
orn
xnor
addx
op3 Instruction
jumpl
rett
ticc
iflush
save
restore
<unused>
<unused>
See page 235 for a complete list
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

9. Format Three Instructions
Not all possible bits patterns are used
op = 11
op3 Instruction ld
ldub
lduh
ldd st
stb
sth
std
<unused>
See page 236 for a complete list
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C

10. Example Decode the following commands: 0x9de3bfa0 0xd007bfec
0x81c7e008
0x81e80000
save %sp, -96, %sp
ld [%fp-20], %o0
mov 4, %o1
add %o0, %o1, %o0
st %o0, [%fp-20]
ret
restore
Richard P. Paul, SPARC Architecture, Assembly Language Programming, and C