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This section will not demonstrate the output of the option -S, --asm-display, since it outputs the long Tiger runtime. Once the registers allocated (i.e., once -s, --asm-compute executed) the option -I, --instr-display produces the code without the runtime. In short: we use -sI instead of -S to save place.
Allocating registers in the main function, when there is no register
pressure is easy, as, in particular, there are no spills. A direct
consequence is that many move are now useless, and have
disappeared. For instance (File 4.85, see Example 4.125):
1 + 2 * 3
$ tc -sI seven.tig
# == Final assembler ouput. == #
# Routine: _main
tc_main:
# Allocate frame
l0:
li $t1, 1
li $t0, 2
mul $t0, $t0, 3
add $t0, $t1, $t0
l1:
# Deallocate frame
jr $ra
$ tc -S seven.tig >seven.s
$ nolimips -l nolimips -Ne seven.s
Another means to display the result of register allocation consists in
reporting the mapping from temps to actual registers:
$ tc -s --tempmap-display seven.tig /* Temporary map. */ fp -> $fp rv -> $v0 t1 -> $t1 t2 -> $t0 t3 -> $t0 t4 -> $t0 t5 -> $s0 t6 -> $s1 t7 -> $s2 t8 -> $s3 t9 -> $s4 t10 -> $s5 t11 -> $s6 t12 -> $s7 t13 -> $ra
Of course it is much better to see what is going on:
(print_int(1 + 2 * 3); print("\n"))
$ tc -sI print-seven.tig
# == Final assembler ouput. == #
.data
l0:
.word 1
.asciiz "\n"
.text
# Routine: _main
tc_main:
sw $fp, -4 ($sp)
move $fp, $sp
sub $sp, $sp, 8
sw $ra, ($fp)
l1:
li $t0, 1
li $ra, 2
mul $ra, $ra, 3
add $a0, $t0, $ra
jal tc_print_int
la $a0, l0
jal tc_print
l2:
lw $ra, ($fp)
move $sp, $fp
lw $fp, -4 ($fp)
jr $ra
$ tc -S print-seven.tig >print-seven.s
$ nolimips -l nolimips -Ne print-seven.s 7
To torture your compiler, you ought to use many temporaries. To be honest, ours is quite slow, it spends way too much time in register allocation.
let
var a00 := 00 var a55 := 55
var a11 := 11 var a66 := 66
var a22 := 22 var a77 := 77
var a33 := 33 var a88 := 88
var a44 := 44 var a99 := 99
in
print_int(0
+ a00 + a00 + a55 + a55
+ a11 + a11 + a66 + a66
+ a22 + a22 + a77 + a77
+ a33 + a33 + a88 + a88
+ a44 + a44 + a99 + a99);
print("\n")
end
$ tc -eIs --tempmap-display -I --time-report print-many.tig
error→Execution times (seconds)
error→ 1: parse : 0.01 ( 50%) 0 ( 0%) 0.01 ( 100%)
error→ 9: asm-compute : 0.01 ( 50%) 0 ( 0%) 0 ( 0%)
error→ rest : 0.02 ( 100%) 0 ( 0%) 0.01 ( 100%)
error→Cumulated times (seconds)
error→ 1: parse : 0.01 ( 50%) 0 ( 0%) 0.01 ( 100%)
error→ rest : 0.02 ( 100%) 0 ( 0%) 0.01 ( 100%)
error→ TOTAL (seconds) : 0.02 user, 0 system, 0.01 wall
# == Final assembler ouput. == #
.data
l0:
.word 1
.asciiz "\n"
.text
# Routine: _main
tc_main:
# Allocate frame
move $x41, $ra
move $x33, $s0
move $x34, $s1
move $x35, $s2
move $x36, $s3
move $x37, $s4
move $x38, $s5
move $x39, $s6
move $x40, $s7
l1:
li $x0, 0
li $x1, 55
li $x2, 11
li $x3, 66
li $x4, 22
li $x5, 77
li $x6, 33
li $x7, 88
li $x8, 44
li $x9, 99
li $x11, 0
add $x12, $x11, $x0
add $x13, $x12, $x0
add $x14, $x13, $x1
add $x15, $x14, $x1
add $x16, $x15, $x2
add $x17, $x16, $x2
add $x18, $x17, $x3
add $x19, $x18, $x3
add $x20, $x19, $x4
add $x21, $x20, $x4
add $x22, $x21, $x5
add $x23, $x22, $x5
add $x24, $x23, $x6
add $x25, $x24, $x6
add $x26, $x25, $x7
add $x27, $x26, $x7
add $x28, $x27, $x8
add $x29, $x28, $x8
add $x30, $x29, $x9
add $x31, $x30, $x9
move $a0, $x31
jal tc_print_int
la $x32, l0
move $a0, $x32
jal tc_print
l2:
move $s0, $x33
move $s1, $x34
move $s2, $x35
move $s3, $x36
move $s4, $x37
move $s5, $x38
move $s6, $x39
move $s7, $x40
move $ra, $x41
# Deallocate frame
jr $ra
/* Temporary map. */
fp -> $fp
rv -> $v0
t0 -> $t9
t1 -> $t8
t2 -> $t7
t3 -> $t6
t4 -> $t5
t5 -> $t4
t6 -> $t3
t7 -> $t2
t8 -> $t1
t9 -> $t0
t11 -> $ra
t12 -> $ra
t13 -> $ra
t14 -> $ra
t15 -> $ra
t16 -> $ra
t17 -> $ra
t18 -> $ra
t19 -> $ra
t20 -> $ra
t21 -> $ra
t22 -> $ra
t23 -> $ra
t24 -> $ra
t25 -> $ra
t26 -> $ra
t27 -> $ra
t28 -> $ra
t29 -> $ra
t30 -> $ra
t31 -> $a0
t32 -> $a0
t33 -> $s0
t34 -> $s1
t35 -> $s2
t36 -> $s3
t37 -> $s4
t38 -> $s5
t39 -> $s6
t40 -> $s7
t110 -> $ra
t111 -> $ra
# == Final assembler ouput. == #
.data
l0:
.word 1
.asciiz "\n"
.text
# Routine: _main
tc_main:
sw $fp, -4 ($sp)
move $fp, $sp
sub $sp, $sp, 8
sw $ra, ($fp)
l1:
li $t9, 0
li $t8, 55
li $t7, 11
li $t6, 66
li $t5, 22
li $t4, 77
li $t3, 33
li $t2, 88
li $t1, 44
li $t0, 99
li $ra, 0
add $ra, $ra, $t9
add $ra, $ra, $t9
add $ra, $ra, $t8
add $ra, $ra, $t8
add $ra, $ra, $t7
add $ra, $ra, $t7
add $ra, $ra, $t6
add $ra, $ra, $t6
add $ra, $ra, $t5
add $ra, $ra, $t5
add $ra, $ra, $t4
add $ra, $ra, $t4
add $ra, $ra, $t3
add $ra, $ra, $t3
add $ra, $ra, $t2
add $ra, $ra, $t2
add $ra, $ra, $t1
add $ra, $ra, $t1
add $ra, $ra, $t0
add $a0, $ra, $t0
jal tc_print_int
la $a0, l0
jal tc_print
l2:
lw $ra, ($fp)
move $sp, $fp
lw $fp, -4 ($fp)
jr $ra
Next: TC-9 Given Code, Previous: TC-9 Goals, Up: TC-9 [Contents][Index]