ST20-C1 datasheet(182/205 Pages) STMICROELECTRONICS

182 / 205 page

182/205

}

else if (X > cm)

... similar

else

... jump table code

where

jump table code is

X; ldc ci; sub; ldc jump_size; mul; ldc (jump_table-M); ldpi

add; jab;

jump_table:

j case_0; j case_1; ... ; j case_k

ERROR:

...

error code

Li:

...

code for Pi

...

Lm:

...

code for Pm

The code at

jump_table consists of a sequence of jump instructions which transfer

control to the relevant branch

Li ... Lm or to ERROR. The destination, case_x,of

each of these jumps is

Lj if cj is equal to (ci + x) and is ERROR otherwise.

The code at

ERROR should be the same code as used at the end of an IF statement

where all the conditionals have been

false. The add, ldpi and jab instructions are

explained in other sections.

All the jumps in the

jump_table code must be encoded to the same length (jump_size

bytes) to enable them to be accessed as a byte array.

nop, which is a two byte instruc-

tion that performs no operation, can be used to ensure this where different operands

require a different amount of prefixing.

Also note that in the special case where

jump_size is 1, ‘ldc jump_size; mul’ can be

removed from the sequence, and where

jump_size is 4, ‘ldc jump_size; mul’ can be

removed provided

add is replaced with wsub.

C.3

Expression evaluation order

Let

depth(e) be the number of stack locations needed for the evaluation of expression

e, defined b y

depth(constant)

= 1

depth(variable)

= 1

depth(function call)

= ‘infinite’

depth(e1 op e2)

= if (depth(e1) > depth(e2))

depth(e1)

else if (depth(e1) < depth(e2))

depth(e2)

else

depth(e1) + 1

That is, if the depth required for each expression is the same, then one extra stack

location is required to store the result of the first expression, while the second expres-

sion is being evaluated. If the stack requirements for each expression are different,

ST20-C1 Datasheet(PDF) 182 Page - STMicroelectronics

ST20-C1 Datasheet(HTML) 182 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL