Difference between revisions of "SCI/Specifications/SCI virtual machine/The Sierra PMachine"

     ldi byte 2

     ldi byte 2

     push

     push

Relative addresses are signed values.

Relative addresses are signed values.

     pTos y ; push the y property

     pTos y ; push the y property

     callk OnControl, 6

     callk OnControl, 6

Notice that, although the <tt>callk</tt> line specifies 6 bytes of parameters, the kernel routine has access to the list size (which is at offset 8)!

Notice that, although the <tt>callk</tt> line specifies 6 bytes of parameters, the kernel routine has access to the list size (which is at offset 8)!

pop(): sp -= 2; return *sp;

pop(): sp -= 2; return *sp;

push(x): *sp = x; sp += 2; return x;

push(x): *sp = x; sp += 2; return x;

The following rules apply to opcodes:

The following rules apply to opcodes:

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc ^= 0xffff;

acc ^= 0xffff;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc += pop();

acc += pop();

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = pop() - acc;

acc = pop() - acc;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc *= pop();

acc *= pop();

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = pop() / acc;

acc = pop() / acc;

Division by zero is caught => acc = 0.

Division by zero is caught => acc = 0.

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = pop() % acc;

acc = pop() % acc;

Modulo by zero is caught => acc = 0.

Modulo by zero is caught => acc = 0.

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = pop() >> acc;

acc = pop() >> acc;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = pop() << acc;

acc = pop() << acc;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc ^= pop();

acc ^= pop();

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc &= pop();

acc &= pop();

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc |= pop();

acc |= pop();

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = -acc;

acc = -acc;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = !acc;

acc = !acc;

prev = acc;

prev = acc;

acc = (acc == pop());

acc = (acc == pop());

prev = acc;

prev = acc;

acc = !(acc == pop());

acc = !(acc == pop());

prev = acc;

prev = acc;

acc = (pop() > acc);

acc = (pop() > acc);

prev = acc;

prev = acc;

acc = (pop() >= acc);

acc = (pop() >= acc);

prev = acc;

prev = acc;

acc = (pop() < acc);

acc = (pop() < acc);

prev = acc;

prev = acc;

acc = (pop() <= acc);

acc = (pop() <= acc);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = (pop() > acc);

acc = (pop() > acc);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = (pop() >= acc);

acc = (pop() >= acc);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = (pop() < acc);

acc = (pop() < acc);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = (pop() >= acc);

acc = (pop() >= acc);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

if (acc) pc += relpos;

if (acc) pc += relpos;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

if (!acc) pc += relpos;

if (!acc) pc += relpos;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

pc += relpos;

pc += relpos;

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

acc = data;

acc = data;

:Sign extension is done for 0x35 if required.

:Sign extension is done for 0x35 if required.

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

push(acc)

push(acc)

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

push(data)

push(data)

:Sign extension for 0x39 is performed where required.

:Sign extension for 0x39 is performed where required.

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

pop();

pop();

:For confirmation: Yes, this simply tosses the TOS value away.

:For confirmation: Yes, this simply tosses the TOS value away.

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

push(*TOS);

push(*TOS);

<syntaxhighlight lang="C">

<syntaxhighlight lang="C">

sp += (size * 2);

sp += (size * 2);

sp -= (framesize + 2 + &rest_modifier);

sp -= (framesize + 2 + &rest_modifier);

&rest_modifier = 0;

&rest_modifier = 0;

:This calls a script subroutine at the relative position relpos, setting up the <tt>ParmVar</tt> pointer first. <tt>ParmVar points</tt> to sp-<tt>''framesize''</tt> (but see also the <tt>&rest</tt> operation). The number of parameters is stored at word offset <tt>-1</tt> relative to <tt>ParmVar</tt>.

:This calls a script subroutine at the relative position relpos, setting up the <tt>ParmVar</tt> pointer first. <tt>ParmVar points</tt> to sp-<tt>''framesize''</tt> (but see also the <tt>&rest</tt> operation). The number of parameters is stored at word offset <tt>-1</tt> relative to <tt>ParmVar</tt>.

&rest_modifier = 0;

&rest_modifier = 0;

(call kernel function kfunct)

(call kernel function kfunct)

sp -= (framesize + 2 + &rest_modifier);

sp -= (framesize + 2 + &rest_modifier);

&rest_modifier = 0;

&rest_modifier = 0;

:This operation starts a new execution loop at the beginning of script 0, public method <tt>dispindex</tt> (Each script comes with a dispatcher list (type 7) that identifies public methods). Parameters are handled as in the call operation.

:This operation starts a new execution loop at the beginning of script 0, public method <tt>dispindex</tt> (Each script comes with a dispatcher list (type 7) that identifies public methods). Parameters are handled as in the call operation.

sp -= (framesize + 2 + &rest_modifier);

sp -= (framesize + 2 + &rest_modifier);

&rest_modifier = 0;

&rest_modifier = 0;

:This operation performs a function call (implicitly placing the current program counter on the execution stack) to an ``external'' procedure of a script. More precisely, exported procedure <tt>dispindex</tt> of script <tt>script</tt> is invoked, where <tt>dispindex</tt> is an offset into the script's Exports list (i.e., <tt>dispindex = ''n'' * 2</tt> references the ''n''th exported procedure).

:This operation performs a function call (implicitly placing the current program counter on the execution stack) to an ``external'' procedure of a script. More precisely, exported procedure <tt>dispindex</tt> of script <tt>script</tt> is invoked, where <tt>dispindex</tt> is an offset into the script's Exports list (i.e., <tt>dispindex = ''n'' * 2</tt> references the ''n''th exported procedure).

:The ``Exports list'' is defined in the script's type 7 object (cf. section [[SCI/Specifications/SCI_virtual_machine/Introduction#Script_resources|Script resources]]). It is an error to invoke a script which does not exist or which does not provide an Exports list, or to use a dispatch index which does not point into an even address within the Exports list.

:The ``Exports list'' is defined in the script's type 7 object (cf. section [[SCI/Specifications/SCI_virtual_machine/Introduction#Script_resources|Script resources]]). It is an error to invoke a script which does not exist or which does not provide an Exports list, or to use a dispatch index which does not point into an even address within the Exports list.

   push0        ; This will read foo and return the value in acc.

   push0        ; This will read foo and return the value in acc.

   send 12      ; This operation does three quite different things.

   send 12      ; This operation does three quite different things.

   return &((vars[(vt >> 1) &amp; 3])[vt &amp; 0x10 ? vi+acc : vi]);

   return &((vars[(vt >> 1) &amp; 3])[vt &amp; 0x10 ? vi+acc : vi]);

}

}

;<nowiki>op 0x5d: selfID (1 bytes)</nowiki>

;<nowiki>op 0x5d: selfID (1 bytes)</nowiki>

:Get 'self' identity: SCI uses heap pointers to identify objects, so this operation sets the accumulator to the address of the current object.

:Get 'self' identity: SCI uses heap pointers to identify objects, so this operation sets the accumulator to the address of the current object.

;<nowiki>op 0x61: pprev (1 bytes)</nowiki>

;<nowiki>op 0x61: pprev (1 bytes)</nowiki>

:Push prev: Pushes the value of the prev register, set by the last comparison bytecode (eq?, lt?, etc.), on the stack.

:Push prev: Pushes the value of the prev register, set by the last comparison bytecode (eq?, lt?, etc.), on the stack.

;<nowiki>op 0x73: lofsa B offset (2 bytes)</nowiki>

;<nowiki>op 0x73: lofsa B offset (2 bytes)</nowiki>

:Load Offset to Accumulator:

:Load Offset to Accumulator:

:Adds a value to the post-operation pc and stores the result in the accumulator.

:Adds a value to the post-operation pc and stores the result in the accumulator.

;<nowiki>op 0x75: lofss B offset (2 bytes)</nowiki>

;<nowiki>op 0x75: lofss B offset (2 bytes)</nowiki>

:Load Offset to Stack:

:Load Offset to Stack:

:Adds a value to the post-operation pc and pushes the result on the stack.

:Adds a value to the post-operation pc and pushes the result on the stack.

;<nowiki>op 0x77: push0 (1 bytes)</nowiki>

;<nowiki>op 0x77: push0 (1 bytes)</nowiki>

:Push 0:

:Push 0:

;<nowiki>op 0x79: push1 (1 bytes)</nowiki>

;<nowiki>op 0x79: push1 (1 bytes)</nowiki>

:Push 1:

:Push 1:

;<nowiki>op 0x7b: push2 (1 bytes)</nowiki>

;<nowiki>op 0x7b: push2 (1 bytes)</nowiki>

:Push 2:

:Push 2:

;<nowiki>op 0x7d: pushSelf (1 bytes)</nowiki>

;<nowiki>op 0x7d: pushSelf (1 bytes)</nowiki>

:Push self:

:Push self: