.bp
.AP "AN EXAMPLE PROGRAM"
.PP
.na
.ta 4n 8n 12n 16n 20n
.nf
1 program example(output);
2 {This program just demonstrates typical EM code.}
3 type rec = record r1: integer; r2:real; r3: boolean end;
4 var mi: integer; mx:real; r:rec;
5
6 function sum(a,b:integer):integer;
7 begin
8 sum := a + b
9 end;
10
11 procedure test(var r: rec);
12 label 1;
13 var i,j: integer;
14 x,y: real;
15 b: boolean;
16 c: char;
17 a: array[1..100] of integer;
18
19 begin
20 j := 1;
21 i := 3 * j + 6;
22 x := 4.8;
23 y := x/0.5;
24 b := true;
25 c := 'z';
26 for i:= 1 to 100 do a[i] := i * i;
27 r.r1 := j+27;
28 r.r3 := b;
29 r.r2 := x+y;
30 i := sum(r.r1, a[j]);
31 while i > 0 do begin j := j + r.r1; i := i - 1 end;
32 with r do begin r3 := b; r2 := x+y; r1 := 0 end;
33 goto 1;
34 1: writeln(j, i:6, x:9:3, b)
35 end; {test}
36 begin {main program}
37 mx := 15.96;
38 mi := 99;
39 test(r)
40 end.
.fi
.ad
.bp
The EM code as produced by the Pascal-VU compiler is given below. Comments
have been added manually. Note that this code has already been optimized.
.LP
.na
.nf
.ta 1n 24n
mes 2,2,2 ; wordsize 2, pointersize 2
\&.1
rom 't.p\e000' ; the name of the source file
hol 552,\-32768,0 ; externals and buf occupy 552 bytes
exp $sum ; sum can be called from other modules
pro $sum,2 ; procedure sum ; 2 bytes local storage
lin 8 ; code from source line 8
ldl 0 ; load two locals ( a and b )
adi 2 ; add them
ret 2 ; return the result
end 2 ; end of procedure ( still two bytes local storage )
\&.2
rom 1,99,2 ; descriptor of array a[]
exp $test ; the compiler exports all level 0 procedures
pro $test,226 ; procedure test, 226 bytes local storage
\&.3
rom 4.8F8 ; assemble Floating point 4.8 (8 bytes) in
\&.4 ; global storage
rom 0.5F8 ; same for 0.5
mes 3,\-226,2,2 ; compiler temporary not referenced by address
mes 3,\-24,2,0 ; the same is true for i, j, b and c in test
mes 3,\-22,2,0
mes 3,\-4,2,0
mes 3,\-2,2,0
mes 3,\-20,8,0 ; and for x and y
mes 3,\-12,8,0
lin 20 ; maintain source line number
loc 1
stl \-4 ; j := 1
lni ; lin 21 prior to optimization
lol \-4
loc 3
mli 2
loc 6
adi 2
stl \-2 ; i := 3 * j + 6
lni ; lin 22 prior to optimization
lae .3
loi 8
lal \-12
sti 8 ; x := 4.8
lni ; lin 23 prior to optimization
lal \-12
loi 8
lae .4
loi 8
dvf 8
lal \-20
sti 8 ; y := x / 0.5
lni ; lin 24 prior to optimization
loc 1
stl \-22 ; b := true
lni ; lin 25 prior to optimization
loc 122
stl \-24 ; c := 'z'
lni ; lin 26 prior to optimization
loc 1
stl \-2 ; for i:= 1
2
lol \-2
dup 2
mli 2 ; i*i
lal \-224
lol \-2
lae .2
sar 2 ; a[i] :=
lol \-2
loc 100
beq *3 ; to 100 do
inl \-2 ; increment i and loop
bra *2
3
lin 27
lol \-4
loc 27
adi 2 ; j + 27
sil 0 ; r.r1 :=
lni ; lin 28 prior to optimization
lol \-22 ; b
lol 0
stf 10 ; r.r3 :=
lni ; lin 29 prior to optimization
lal \-20
loi 16
adf 8 ; x + y
lol 0
adp 2
sti 8 ; r.r2 :=
lni ; lin 30 prior to optimization
lal \-224
lol \-4
lae .2
lar 2 ; a[j]
lil 0 ; r.r1
cal $sum ; call now
asp 4 ; remove parameters from stack
lfr 2 ; get function result
stl \-2 ; i :=
4
lin 31
lol \-2
zle *5 ; while i > 0 do
lol \-4
lil 0
adi 2
stl \-4 ; j := j + r.r1
del \-2 ; i := i - 1
bra *4 ; loop
5
lin 32
lol 0
stl \-226 ; make copy of address of r
lol \-22
lol \-226
stf 10 ; r3 := b
lal \-20
loi 16
adf 8
lol \-226
adp 2
sti 8 ; r2 := x + y
loc 0
sil \-226 ; r1 := 0
lin 34 ; note the absence of the unnecessary jump
lae 22 ; address of output structure
lol \-4
cal $_wri ; write integer with default width
asp 4 ; pop parameters
lae 22
lol \-2
loc 6
cal $_wsi ; write integer width 6
asp 6
lae 22
lal \-12
loi 8
loc 9
loc 3
cal $_wrf ; write fixed format real, width 9, precision 3
asp 14
lae 22
lol \-22
cal $_wrb ; write boolean, default width
asp 4
lae 22
cal $_wln ; writeln
asp 2
ret 0 ; return, no result
end 226
exp $_main
pro $_main,0 ; main program
\&.6
con 2,\-1,22 ; description of external files
\&.5
rom 15.96F8
fil .1 ; maintain source file name
lae .6 ; description of external files
lae 0 ; base of hol area to relocate buffer addresses
cal $_ini ; initialize files, etc...
asp 4
lin 37
lae .5
loi 8
lae 2
sti 8 ; mx := 15.96
lni ; lin 38 prior to optimization
loc 99
ste 0 ; mi := 99
lni ; lin 39 prior to optimization
lae 10 ; address of r
cal $test
asp 2
loc 0 ; normal exit
cal $_hlt ; cleanup and finish
asp 2
end 0
mes 5 ; reals were used
.fi
.ad
.PP
The compact code corresponding to the above program is listed below.
Read it horizontally, line by line, not column by column.
Each number represents a byte of compact code, printed in decimal.
The first two bytes form the magic word.
.LP
.Dr 33
173 0 159 122 122 122 255 242 1 161 250 124 116 46 112 0
255 156 245 40 2 245 0 128 120 155 249 123 115 117 109 160
249 123 115 117 109 122 67 128 63 120 3 122 88 122 152 122
242 2 161 121 219 122 255 155 249 124 116 101 115 116 160 249
124 116 101 115 116 245 226 0 242 3 161 253 128 123 52 46
56 255 242 4 161 253 128 123 48 46 53 255 159 123 245 30
255 122 122 255 159 123 96 122 120 255 159 123 98 122 120 255
159 123 116 122 120 255 159 123 118 122 120 255 159 123 100 128
120 255 159 123 108 128 120 255 67 140 69 121 113 116 68 73
116 69 123 81 122 69 126 3 122 113 118 68 57 242 3 72
128 58 108 112 128 68 58 108 72 128 57 242 4 72 128 44
128 58 100 112 128 68 69 121 113 98 68 69 245 122 0 113
96 68 69 121 113 118 182 73 118 42 122 81 122 58 245 32
255 73 118 57 242 2 94 122 73 118 69 220 10 123 54 118
18 122 183 67 147 73 116 69 147 3 122 104 120 68 73 98
73 120 111 130 68 58 100 72 136 2 128 73 120 4 122 112
128 68 58 245 32 255 73 116 57 242 2 59 122 65 120 20
249 123 115 117 109 8 124 64 122 113 118 184 67 151 73 118
128 125 73 116 65 120 3 122 113 116 41 118 18 124 185 67
152 73 120 113 245 30 255 73 98 73 245 30 255 111 130 58
100 72 136 2 128 73 245 30 255 4 122 112 128 69 120 104
245 30 255 67 154 57 142 73 116 20 249 124 95 119 114 105
8 124 57 142 73 118 69 126 20 249 124 95 119 115 105 8
126 57 142 58 108 72 128 69 129 69 123 20 249 124 95 119
114 102 8 134 57 142 73 98 20 249 124 95 119 114 98 8
124 57 142 20 249 124 95 119 108 110 8 122 88 120 152 245
226 0 155 249 125 95 109 97 105 110 160 249 125 95 109 97
105 110 120 242 6 151 122 119 142 255 242 5 161 253 128 125
49 53 46 57 54 255 50 242 1 57 242 6 57 120 20 249
124 95 105 110 105 8 124 67 157 57 242 5 72 128 57 122
112 128 68 69 219 110 120 68 57 130 20 249 124 116 101 115
116 8 122 69 120 20 249 124 95 104 108 116 8 122 152 120
159 124 160 255 159 125 255
.De