Assembly Programming

1
Assembly Programming
2
SPARC Language Program Skeleton

• .global main
• main
• save sp, -96, sp
• ... other code ...
• mov 1, g1
• ta 0

• .global main
• main
• save sp, -96, sp
• ... other code ...
• ret
• restore

Execution always starts at the label main
Trap back to the operating system
Normal exit procedure
3
SPARC Instruction

• Standard Format
• ltopgt src_reg, src_reg, dest_reg
• ltopgt src_reg, immediate, dest_reg ! -4096
  lt immediate lt 4096
• synthetic instructions
• clr reg
  gt or g0, g0, reg
• mov immediate, dest_reg gt or
  g0, immediate, dest_reg
• mov src_reg, dest_reg gt or
  g0, src_reg, dest_reg

4
Registers

• g0 r0 (always zero)
• g1 r1
• g7 r7
• o0 r8
• o6 r14 sp
• o7 r15 for return address
• l0 r16
• l7 r23
• i0 r24
• i6 r30 fp
• i7 r31 for return address

5
Example

• .global main
• main
• save sp,-96,sp
• mov 9, l0
• sub l0, 1, o0
• sub l0, 7, o1
• call .mul
• nop
• sub l0, 0xb, o1
• call .div
• nop
• mov o0, l1
• mov 1, g1
• ta 0

6
SPARC control structures

• Condition codes
• N -- negative contains status of result
  from last instruction
• Z -- zero
• V -- overflow
• C -- carry
• Branches
• ba
• bneg
• bg

7
Control Structure

• while ( a lt 17 ) test
• a a b cmp a_r,
  17
• c bg done
  
• nop
• add
  a_r, b_r, a_r
• add
  c_r, 1, c_r
• ba
  test
• nop
• done

8
Control Structure

• for ( a 1 a lt b a )
  mov 1,a_r
• c a
  test
• 
  cmp a_r,b_r
• 
  bg done
• 
  nop
• rewritten as while loop
  mov a_r, o0
• 
  mov c_r, o1
• a 1
  call .mul
• while ( a lt b )
  nop
• c a
  mov o0, c_r
• a
  add a_r, 1, a_r
• 
  ba test
• 
  nop
• 
  done

9
Control Structure

• if ( (a b) gt c )
  add a_r, b_r, o0
• a b
  cmp o0, c_r
• 
  ble next
• 
  nop
• 
  add a_r, b_r, a_r
• 
  next

10
Control Structure

• if ( a ! b ) cmp
  a_r, b_r
• c 1 be
  else_part
• else nop
• c 0 then_part
• 
  mov 1, c_r
• 
  ba next
• 
  nop
• else_part
• 
  mov 0, c_r
• next

11
Arrays

• void prt_sum( int x, int n )
• register int i, sum 0
• for( i 0 i lt n i )
• sum sum xi
• printf("d\n",sum)

12
Arrays

• .global main
• main
• save sp, -96, sp
• clr l0
• clr l1
• mov i0, l
• loop
• cmp l0, i1
• bge done
• nop
• ld l2, o0
• add l1, o0, l1
• add l2, 4, l2
• inc l0
• ba loop
• nop
• done
• set fmt, o0
• mov l1, o0