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 )

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

Example (cont.)... add %o0, offs, %l1 ! f = result + offs mov 1, %g1 ! Trap dispatch ta 0 ! Trap to system

Filling Delay Slots Not very efficient 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 9, %o0 ! 9 into %o0 for multiplication call.mul ! Result in %o0 mov %l0, %o1 ! c into %o1 for multiplication Better!

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...

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

Delayed Control Transfer Increases the efficiency of pipelining

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...

Example (cont.)... add %o0, offs, %l1 ! f = result + offs add %l0, 1, %l0 ! c++ cmp %l0, 21 ! c < 21 ? bl loop nop ! Delay slot mov 1, %g1 ! Trap dispatch ta 0 ! Trap to system

Annulled Branches Delay slot instruction is ignored –Conditional: if branch is not taken –Unconditional: always annulled

An Annulled Branch Java/C Code: while (a <= 17) a = a + b; Unoptimised assembler: ! Assumes a is in %l0 and b is in %l1 b test ! See if loop should execute nop ! Delay slot loop: add %l0, %l1, %l0! a = a + b test: cmp %l0, 17 ! a <= 17 ble loop ! If so branch back to start nop ! Delay slot

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 <= 17 ble,a loop ! If so branch back to start add %l0, %l1, %l0 ! a = a + b

4. Logical and Arithmetic Operations Logical Operators –and or xor –xnor andn orn –+ cc to set the condition codes Shift Operators –sra srl sll

Arithmetic Operators Only addition and subtraction –add[x][cc] –sub[x][cc] [x] — with carry [cc] — to set the flags

Multiplication Long multiplication is supported by the “multiply step” instruction: –mulscc

Division Use the standard routines: –.div.rem –.udiv.urem