1.2.0

## Instructions

The virtual machine instructions are contained in `vm/instructions.def`. The documentation below is generated by `rakelib/vm.rake`.

### noop()

The classic no-op operator. It performs no actions and does not modify the stack.

Before | After
--- | ---
... | ...

#### See Also

- pop

### push_nil()

The special object `nil` is pushed onto the stack.

Before | After
--- | ---
... | nil
| ...

### push_true()

The special value `true` is pushed onto the stack.

Before | After
--- | ---
... | true
| ...

### push_false()

The special object `false` is pushed onto the stack.

Before | After
--- | ---
... | false
| ...

### push_int(number)

Pushes the value of the integer literal onto the stack.

Before | After
--- | ---
... | number
| ...

#### Notes

Certain common cases (i.e. -1, 0, 1, and 2) are optimised to avoid the decoding of the argument.

#### See Also

- meta_push_0
- meta_push_1
- meta_push_2
- meta_push_neg_1

### push_self()

The current `self` object is pushed onto the stack.

Before | After
--- | ---
... | self
| ...

### set_literal(literal)

Used to set the value of a literal. The stack top is set to the literal indicated by the operand.

Before | After
--- | ---
value | value
... | ...

#### Notes

Unlike other literals such as strings and numbers, creating a Regexp literal (i.e. via the /regex/ syntax) is a two step process to create the literal slot for the Regexp, create a literal for the string between the ‘/’ delimiters and create a new Regexp object passing it the string. Only then can the literal value be set, using the set_literal opcode.

### push_literal(literal)

The value identified by the operand literal in the current state literals tuple is retrieved and placed onto the stack.

Before | After
--- | ---
... | literal
| ...

#### Notes

The literals tuple is part of the machine state, and holds all literal objects defined or used within a particular scope.

### goto(location)

Unconditionally moves the instruction pointer to the position specified by location.

Before | After
--- | ---
... | ...

#### Notes

All goto instructions use absolute addressing. This is absolute movement rather than a relative one, so the operand must specify the ip starting from 0 to move to.

#### See Also

- goto_if_true
- goto_if_false

### goto_if_false(location)

Remove the top value on the stack, and if `nil` or `false`, set the instruction pointer to the value specified by location.

Before | After
--- | ---
value | ...
... |

#### See Also

- goto
- goto_if_true

### goto_if_true(location)

Remove the top value on the stack, and if not `nil` or `false`, set the instruction pointer to the value specified by location.

Before | After
--- | ---
value | ...
... |

#### See Also

- goto
- goto_if_false

### ret()

Return a value to the direct caller

Pops the top value from the stack, and returns to the direct caller of the current invocation.

Before | After
--- | ---
value | value
... | ...

#### Notes

In a method, the `return` keyword uses this instruction. In a block though, `return` uses the raise_return instruction and `next` uses this instruction.

#### See Also

- raise_return
- raise_exc

### swap_stack()

Swaps the top two values on the stack, so that the second value becomes the first, and the first value becomes the second.

Before | After
--- | ---
s0 | s1
s1 | s0
... | ...

### dup_top()

Read a value from the top of the stack and push it on the stack again without removing the original value.

Before | After
--- | ---
s0 | s0
... | s0
| ...

### dup_many(count)

Duplicate multiple values on the stack

Read count values from the stack and push them onto the stack again in order without removing the original values.

Before | After
--- | ---
value1 | value1
value2 | value2
... | value1
| value2
| ...

### pop()

Removes the top value from the stack, discarding it.

Before | After
--- | ---
value | ...
... |

#### Notes

Pop is typically used when the return value of another opcode is not required.

### pop_many(count)

Removes count values from the stack and discard them.

Before | After
--- | ---
value1 | ...
value2 |
... |

### rotate(count)

Reverses the order on the stack of the top count values.

Before | After
--- | ---
obj1 | obj3
obj2 | obj2
obj3 | obj1
... | ...

### move_down(positions)

The top value on the stack is moved down by the specified number of positions, with all values above that position shuffling up by one.

Before | After
--- | ---
obj1 | obj2
obj2 | ...
... | objn
objn | obj1

### set_local(local)

Read the top of the stack and set the local variable identified by operand local to it. The stack is not modified by this instruction.

Before | After
--- | ---
value | value
... | ...

#### See Also

- push_local

### push_local(local)

Retrieves the current value of the local variable referenced by operand local and push it onto the stack.

Before | After
--- | ---
... | value
| ...

#### See Also

- set_local

### push_local_depth(depth, index)

Pushes the value of a local from an enclosing scope onto the stack

Retrieves the value of a local variable. Operand depth indicates how many upward enclosing scopes to walk up and then operand index indicates which local in that context to read. The value is then pushed on the stack.

Before | After
--- | ---
... | value
| ...

#### Example

     k = 0
     foo.each do |i|
       bar.each do |j|
         # i is a local variable from enclosing scope at depth 1
         # k is a local variable from enclosing scope at depth 2
         i = i + j + k
       end
     end

#### See Also

- set_local_depth

### set_local_depth(depth, index)

Updates the value of a local variable contained in an enclosing scope

Read a value from the top of thes stack and use it to update a local variable in an enclosing scope. The depth and index operands indentify the specific local the same as in `push_local_depth`.

Before | After
--- | ---
value | value
... | ...

#### Example

     foo.each do |i|
       bar.each do |j|
         i = i + j  # i is a local variable from enclosing scope at depth 1
       end
     end

#### See Also

- push_local_depth

### passed_arg(index)

Checks if the argument specified by the operand index was passed to the current invocation. If so, push true, otherwise false.

Before | After
--- | ---
... | boolean
| ...

#### Notes

Arguments are specified via a zero-index, so the first argument is 0.

### push_current_exception()

Pushes the current exception onto the stack, so that it can be used for some purpose, such as checking the exception type, setting an exception variable in a rescue clause, etc.

Before | After
--- | ---
... | exception
| ...

#### Example

     begin
       foo = BAR        # BAR is not defined
     rescue NameError   # push_exception used to check type of exception (via ===)
       puts "No BAR"
     end

#### See Also

- raise_exc

### clear_exception()

Clears any exceptions from the current thread.

Before | After
--- | ---
... | ...

### push_exception_state()

Package up the current exception state into an object and push it. This is used to preserve the exception state around code that might mutate it. For instance, when handling an ensure while an exception is being raised

Before | After
--- | ---
... | exc_state
| ...

### restore_exception_state()

Pops a value off the stack and set the threads exception state from it. This instruction is only to be used with a value pushed on the stack by the push_exception_state instruction.

Before | After
--- | ---
exception | ...
... |

#### See Also

- push_exception_state

### raise_exc()

Raises an exception

Pops a value off the stack and make it the current exception. If the value is not an instance of Exception, a TypeError is raised.

Before | After
--- | ---
value | ...
... |

### setup_unwind(ip, type)

Register an unwind handler

Registers what to happen when an exception wants to unwind through the current invocation. Operand ip specifies where to set the instruction pointer if used. Operand type is either 0 for if the value should be used in rescue style (not run when unwinding because of a return caused by `raise_return`) or 1 for ensure style (always used). The registrations are nested within the current invocation and are automatically removed from the registry when they are used. The `pop_unwind` instruction can be used to remove an unused registration.

Before | After
--- | ---
... | ...

#### Notes

The registration also contains the value of the stack depth when created. If the registration is used, then the stack depth is restored to the value contained in the registration

#### See Also

- pop_unwind

### pop_unwind()

Remove the next unused unwind registration from the current invocation. This instruction is paired with `setup_unwind` to remove registrations when control exits a section of code that registered a handler but didn’t use it. For example, exiting a begin that had a rescue expression.

Before | After
--- | ---
... | ...

#### See Also

- setup_unwind

### raise_return()

Cause the toplevel enclosing scope to return

Only used in a block, pop a value from the stack and raise a special internal exceptiion and begin unwinding the stack. The toplevel method scope will rescue the exception and return the value.

Before | After
--- | ---
value | value
... | ...

#### See Also

- ret

### ensure_return()

Return from a scope but run ensures first

A one use instruction, used only in a method toplevel within a begin that has an ensure. Use the same internal exception as `raise_return` which will coax the ensure registration to run.

Before | After
--- | ---
value | value
... | ...

#### See Also

- ret
- raise_return

### raise_break()

Cause the method that yielded the current block to return. Used to implement the `break` keyword in a block.

Before | After
--- | ---
value | value
... | ...

### reraise()

Continue unwinding the stack with the current exception. Verify that there is a current exception, then begin the unwinding process again.

Before | After
--- | ---
... | ...

### make_array(count)

Create an array and populate with values on the stack

Creates a new array, populating its contents by remove the number of values specidied by operand count and putting them into the array in the order they were on the stack. The resulting array is pushed onto the stack.

Before | After
--- | ---
valueN | [value1, value2, ..., valueN]
... | ...
value2 |
value1 |
... |

### cast_array()

Removes the object on the top of the stack, and:

1. If the input is a tuple, a new array object is created based on the tuple data.
2. If the input is an array, it is unmodified.

If the input is any other type, call `Array.coerce_into_array(value)`. If the return value of the method call is an `Array`, make it the result. Otherwise make the result an 1 element `Array` contain the original value.

The resulting array is then pushed back onto the stack.

Before | After
--- | ---
value | array
... | ...

### shift_array()

Pops an array off the top of the stack. If the array is empty, it is pushed back onto the stack, followed by `nil`.

Otherwise, the array is shifted, then pushed back onto the stack, followed by the object that was shifted from the front of the array.

Before | After
--- | ---
[value1, value2, ..., valueN] | value1
... | [value2, ..., valueN]
| ...

### set_ivar(index)

Pops a value off the stack, and uses it to set the value of the instance variable identifies by the literal specified by operand index. The value popped off the stack is then pushed back on again.

Before | After
--- | ---
value | value
... | ...

### push_ivar(index)

Pushes the instance variable identified by index onto the stack.

Before | After
--- | ---
... | value
| ...

### push_const(literal)

Locates the constant indicated by the operand literal from the current context, and pushes it onto the stack. If the constant cannot be found in the current context, nothing is pushed onto the stack, and a NameError exception is raised.

Before | After
--- | ---
... | constant
| ...

#### Example

     engine = RUBY_ENGINE # RUBY_ENGINE is a constant defined by Rubinius

### set_const(index)

Pops an object off the stack, and uses value to set a constant named by the literal index. The value is pushed back onto the stack.

Before | After
--- | ---
value | value
... | ...

### set_const_at(index)

Pop a value from the literals table specified by the operand index and use it as the value of a constant named inside a Module object popped from the stack. The value is pushed back on the stack.

Before | After
--- | ---
value | value
module | ...
... |

### find_const(index)

Pops module off the stack, and searches within its namespace for the constant named by the literal specified by the operand index. If found, it is pushed onto the stack; otherwise, nothing is pushed onto the stack, and a `NameError` exception is raised.

Before | After
--- | ---
module | constant
... | ...

#### Example

     str = "abc"
     enum = Enumerable::Enumerator(str, :each_byte)

### push_cpath_top()

Pushes the top-level global object that represents the top-level namespace for constants. Used to find constants relative to the toplevel. In Ruby, this is the class `Object`.

Before | After
--- | ---
... | constant
| ...

### push_const_fast(literal, association)

Pushes a constant onto the stack. Caches the lookup to provide faster future lookup. This instruction is normally emitted only by the Generator.

Before | After
--- | ---
... | constant
| ...

#### Example

     engine = RUBY_ENGINE # RUBY_ENGINE is a constant defined by Rubinius

#### See Also

- push_const

### set_call_flags(flags)

The call flags on the current execution context are set to the opcode argument flags.

Before | After
--- | ---
... | ...

#### Notes

Currently this only has one use, which is that send_stack_with_splat checks if flags is set to CALL_FLAG_CONCAT which indicase that the splat represents arguments at the beginning rather than the end.

### allow_private()

Indicate that the next send is allowed to see `private` methods.

Before | After
--- | ---
... | ...

### send_method(literal)

Pops a receiver object off the top of the stack and sends it the message specified by the operand literal with zero arguments.

When the method returns, the return value is pushed on the stack.

Before | After
--- | ---
receiver | value
... | ...

#### Notes

This form of send is for methods that take no arguments.

#### See Also

- send_stack

### send_stack(literal, count)

Sends a message with arguments on the stack

Pops the receiver of the message off the stack and sends the message specified by the operand literal with count arguments. The arguments are removed from the stack also.

When the method returns, the return value is pushed on the stack.

Before | After
--- | ---
argN | value
... | ...
arg2 |
arg1 |
receiver |

#### Notes

This opcode does not pass a block to the receiver; see `send_stack_with_block` for the equivalent op code used when a block is to be passed.

#### See Also

- send_stack_with_block

### send_stack_with_block(literal, count)

Sends a message with arguments and a block on the stack

Pops the receiver of the message off the stack and sends the message specified by the operand literal with count arguments. The arguments are removed from the stack also. A value that represents the block to pass on is popped off the stack after the normal arguments.

When the method returns, the return value will be on top of the stack.

Before | After
--- | ---
block | retval
argN | ...
... |
arg2 |
arg1 |
receiver |

#### Notes

This opcode passes a block to the receiver; see `send_stack` for the equivalent op code used when no block is to be passed.

#### See Also

- send_stack

### send_stack_with_splat(literal, count)

Before | After
--- | ---
block | value
array | ...
receiver |
... |

### send_super_stack_with_block(literal, count)

Call a method on the superclass with a block

The same as `send_stack_with_block`, but reciever is the current self instead of being read from the stack, and the method to call is looked up starting with the reciever superclass.

Before | After
--- | ---
block | retval
argN | ...
... |
arg2 |
arg1 |

### send_super_stack_with_splat(literal, count)

Call a method on the superclass, passing args plus a block.

The same as `send_stack_with_block`, but receiver is the current `self` instead of being read from the stack, and the method to call is looked up starting with the receiver superclass.

Before | After
--- | ---
block | retval
argN | ...
... |
arg2 |
arg1 |

### push_block()

Pushes the current block onto the stack. The value is not wrapped in a `Proc` if it is a `BlockEnvironment`.

Before | After
--- | ---
... | block
| ...

#### See Also

- push_proc

### passed_blockarg(count)

Check if exactly count arguments were passed to the current invocation.

Before | After
--- | ---
... | boolean
| ...

#### Notes

This instruction is deprecated and no longer used.

### create_block(literal)

Read a CompiledMethod specified by the operand +literal+ and create a `BlockEnvironment`. Push the new `BlockEnvironment` object on the stack.

Before | After
--- | ---
... | block
| ...

### cast_for_single_block_arg()

Converts the value on the top of the stack into an argument for a block taking one argument.

The value on the top of the stack is popped, and:

If it has no fields, the result is `nil`.

If the value contains a single field, the result is the value in the first field.

Otherwise, package up all the arguments in an `Array` as the result.

The result is then pushed onto the stack.

Before | After
--- | ---
... | argument
| ...

#### Notes

This is a single use instruction, only used to simplify how to handle a block that accepts one argument.

### cast_for_multi_block_arg()

Converts a block argument single-valued tuple into multiple arguments if the arg is an array.

If the Proc invoked from was in lambda mode, and one argument is passed: * and it’s an Array, push it. * and it responds to `#to_ary`, try and convert it and push it. * otherwise wrap it in a one element Array and push it.

Otherwise: Package up the arguments into an `Array` and push it onto the stack.

Before | After
--- | ---
value1 | array[value1,..] | value1
value2 | ...
... |

#### Example

     [[1,2,3]].each do |i,j,k|
       # do something
     end

#### Notes

This is a single use instruction, only used to simplify how to handle a block that accepts 2 or more arguments. The semantics for this instruction change depending on if the current block invocation is from a Proc with lambda semantics or not.

### cast_for_splat_block_arg()

Take all arguments passed to the current invocation and package them into an `Array`, which is then pushed on the stack.

Before | After
--- | ---
... | arguments
| ...

### yield_stack(count)

Invoke the current block, passing count arguments to it.

Before | After
--- | ---
argN | value
... | ...
arg2 |
arg1 |
... |

#### See Also

- send_stack

### yield_splat(count)

Invoke the current block, passing count arguments to it in addition to the values in the `Array` array.

Before | After
--- | ---
array | value
argN | ...
... |
arg2 |
arg1 |
... |

#### See Also

- send_stack_with_splat

### string_append()

Pops two strings off the stack, appends the second to the first, and then pushes the combined string back onto the stack.

Before | After
--- | ---
prefix | string
suffix | ...
... |

#### Notes

The original string is modified by the append.

### string_build(count)

Build a new string using many substrings

Remove count elements from the stack and interpret each as a `String`. Build a new string which is all the removed elements concated together in the order they were on the stack.

Push the resulting string.

Before | After
--- | ---
stringN | string1string2..stringN
... | ...
string2 |
string1 |

### string_dup()

Consume the string on the stack, replacing it with a duplicate. Mutating operations on the original string will not affect the duplicate, and vice-versa.

Before | After
--- | ---
string | string
... | ...

### push_scope()

Pushes the current `StaticScope` object on the stack. Many operations are defered to the current scope. This operation retrieves the current scope so methods can be called on it.

Before | After
--- | ---
... | scope
| ...

### add_scope()

Create a new `StaticScope` object for the given Module on the stack. This scope is chained off the current scope of the method.

This also sets the scope of the current `CompiledMethod` to the new `StaticScope`.

Before | After
--- | ---
module | ...
... |

### push_variables()

Push the `VariableScope` for the current method/block invocation on the stack.

Before | After
--- | ---
... | scope
| ...

### check_interrupts()

Perform required occasional checks that must be done. This instruction is used by loops to allow them to be interrupted externally, and thus also cause the current method to heat up.

Before | After
--- | ---
... | ...

### yield_debugger()

Pauses virtual machine execution and yields control to the debugger on the debug channel. If no debugger is registered, an error is raised.

Before | After
--- | ---
... | ...

#### Notes

This instruction is deprecated and should not be used.

### is_nil()

Pop the value from the stack, and push `true` or `false` depending on whether the consumed value was the special value `nil`.

Before | After
--- | ---
value | boolean
... | ...

### check_serial(literal, serial)

Checks if the specified method serial number matches an expected value.

Pops the receiver object from the stack and checks if it responds to the message specified by the operand literal and the target method has serial number serial. If so, push `true`, else push `false`.

Before | After
--- | ---
receiver | boolean
... | ...

#### Notes

This opcode is typically used to determine at runtime whether an optimisation can be performed. At compile time, two code paths are generated: a slow, but guaranteed correct path, and a fast path that uses certain optimisations. The serial number check is then performed at runtime to determine which code path is executed.

For example, a method such as `Fixnum#times` can be optimised at compile time, but we can’t know until runtime whether or not the `Fixnum#times` method has been overridden. The serial number check is used to determine each time the code is executed, whether or not the standard `Fixnum#times` has been overridden. It leverages the serial number field on a `CompiledMethod`, is initialised to either 0 (for kernel land methods) or 1 (for user land methods).

### check_serial_private(literal, serial)

Checks if the specified method’s serial number matches an expected value. Considers `private` methods too.

Before | After
--- | ---
receiver | boolean
... | ...

#### See Also

- check_serial

### push_my_field(index)

Pushes the value of the specified field in the current object onto the stack.

Before | After
--- | ---
... | value
| ...

#### Notes

Fields are similar to instance variables, but have dedicated storage allocated. They are primarily used on core or bootstap classes. This instruction should not be used directly. The VM will specialize push_ivar instructions into this.

### store_my_field(index)

Stores the value at the top of the stack into the field specified by index on `self`.

The stack is left unmodified.

Before | After
--- | ---
value | value
... | ...

#### Notes

This instruction should not be used directly. The VM will specialize push_ivar instructions into this.

### kind_of()

Evaluate if object is an instance of class or of an ancestor of class. If so, push `true`, else push `false`.

The equivalent of `object.kind_of?(klass)` in Ruby.

Before | After
--- | ---
object | boolean
class | ...
... |

#### See Also

- instance_of

### instance_of()

Evaluate if object is an instance of class. If so, push `true`, else push `false`.

The equivalent of `object.instance_of?(klass)` in Ruby.

Before | After
--- | ---
object | boolean
class | ...
... |

#### See Also

- kind_of

### meta_push_neg_1()

Push `-1` (negative 1) onto the stack.

Before | After
--- | ---
... | value
| ...

#### Notes

This is an optimisation applied by the compiler.

### meta_push_0()

Push `0` (zero) onto the stack.

Before | After
--- | ---
... | value
| ...

#### Notes

This is an optimisation applied by the compiler.

### meta_push_1()

Push `1` (one) onto the stack.

Before | After
--- | ---
... | value
| ...

#### Notes

This is an optimisation applied by the compiler.

### meta_push_2()

Push `2` (two) onto the stack.

Before | After
--- | ---
... | value
| ...

#### Notes

This is an optimisation applied by the compiler.

### meta_send_op_plus(literal)

Implementation of `#+` optimised for `Fixnum`.

Pops value1 and value2 off the stack, and pushes the sum (value1 `+` value2). If both values are Fixnums, the addition is done directly via the `fixnum_add` primitive. Otherwise, the `#+` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | sum
value2 | ...
... |

### meta_send_op_minus(literal)

Implementation of `#-` optimised for `Fixnum`.

Pops value1 and value2 off the stack, and pushes the difference (value1 `-` value2). If both values are Fixnums, the subtraction is done directly via the `fixnum_sub` primitive. Otherwise, the `#-` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | difference
value2 | ...
... |

### meta_send_op_equal(literal)

Implementation of `#==` optimised for `Fixnum` and `Symbol`.

Pops value1 and value2 off the stack and pushes the logical result of (value1 `==` value2). If value1 and value2 are both Fixnums or both Symbols, the comparison is done directly. Otherwise, the `#==` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | boolean
value2 | ...
... |

### meta_send_op_lt(literal)

Implementation of `#<` optimised for `Fixnum`.

Pops value1 and value2 off the stack, and pushes the logical result of (value1 `<` value2). If value1 and value2 are both Fixnums, the comparison is done directly. Otherwise, the `#<` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | boolean
value2 | ...
... |

### meta_send_op_gt(literal)

Implementation of `#>` optimised for `Fixnum`.

Pops value1 and value2 off the stack, and pushes the logical result of (value1 `>` value2). If value1 and value2 are both Fixnums, the comparison is done directly. Otherwise, the `#>` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | boolean
value2 | ...
... |

### meta_send_op_tequal(literal)

Implementation of `#===` (triple equal) optimised for `Fixnum` and `Symbol`.

Pops value1 and value2 off the stack, and pushes the logical result of (value1 `===` value2). If value1 and value2 are both Fixnums or both Symbols, the comparison is done directly. Otherwise, the `#===` method is called on value1, passing value2 as the argument.

Before | After
--- | ---
value1 | boolean
value2 | ...
... |

#### Notes

Exactly like equal, except calls `#===` if it can’t handle it directly.

### meta_send_call(literal, count)

Simplified call instruction used for non-dynamic `yield` calls and for simple calls with static arguments.

Before | After
--- | ---
argN | retval
... |
arg1 |
receiver |

### push_my_offset(index)

Pushes a value read directly from within the body of an object.

Before | After
--- | ---
... | offset
| ...

#### Notes

This instruction must never be used directly. The VM will specialize `push_my_field` instructions into this.

#### See Also

- push_my_field

### zsuper(literal)

Call a superclass method on the current, passing the arguments passed to the current invocation.

Before | After
--- | ---
argN | value
... | ...
arg2 |
arg1 |
... |

#### Notes

This is a specialization of `send_super_with_stack` that is necessary for Ruby semantics regarding how to read the original arguments.

#### See Also

- send_super_with_stack

### push_block_arg()

Push the block passed as an argument to the current invocation. This differs from `push_block` in that in is not the block for the currrent scope because of how the current block is seen within an existing block.

Before | After
--- | ---
... | block
| ...

#### See Also

- push_block

### push_undef()

Push the special undefined value on the stack.

Before | After
--- | ---
... | value
| ...

### push_stack_local(which)

Push the stack local identified by operand which.

Before | After
--- | ---
... | value
| ...

#### Notes

Stack locals differ from normal locals in that they are not viewable by closures.

### set_stack_local(which)

Set the stack local identified by operand which using the value on the top of the stack.

Before | After
--- | ---
value | value
... | ...

#### Notes

Stack locals differ from normal locals in that they are not viewable by closures.

### push_has_block()

Push `true` or `false` based on whether there is a current block.

Before | After
--- | ---
... | value
| ...

#### Notes

Used to implement `block_given?` without having to directly expose the block object itself. This simplifies JIT inlining.

### push_proc()

Wrap the current block in a `Proc` and push it onto the stack. If there is no current block, push `nil`.

Before | After
--- | ---
... | value
| ...

#### Notes

Used to implement `&block` in a method signature.

#### See Also

- push_block

### check_frozen()

Check if the value on the top of the stack is frozen. If so, raise a `TypeError` indicating so.

Before | After
--- | ---
value | value
... | ...

#### Notes

An optimzation to deal with check for frozen.

### cast_multi_value()

Convert a value into an Array

Pop value. If it is an `Array`, push it back on the stack. Otherwise, attempt to convert it to an `Array` using `#to_ary` and push the result. If the value can not be converted to an array, it is wrapped in a one element `Array`.

Before | After
--- | ---
value | array
... | ...

### invoke_primitive(literal, count)

Directly invoke a primitive by name.

Pop count values off the stack and pass them directly to the primitive operation named by the operand literal.

Before | After
--- | ---
argN | value
... | ...
arg2 |
arg1 |

### push_rubinius()

Pushes the top-level global `Rubinius` constant onto the stack. Generally this is done to call a utility method.

Before | After
--- | ---
... | constant
| ...

### call_custom(literal, count)

Invoke a method via the call custom protocol.

Pop the receiver and count values off the stack and begin the call custom invocation protocol with them as arguments.

Before | After
--- | ---
argN | value
... | ...
arg2 |
arg1 |
reciever |

### meta_to_s(literal)

Pop a value off the stack and if it’s not a `String`, call a method indicated by literal on it. Push the resulting object back on the stack.

Before | After
--- | ---
object | string
... | ...

#### Notes

Normally literal is `:to_s`, but this instruction leaves it up to the user to indicate for flexibility.