List of CIL instructions
Appearance
This is a list of the instructions in the instruction set of the Common Intermediate Language bytecode.
- Opcode abbreviated from operation code is the portion of a machine language instruction that specifies the operation to be performed.
- Base instructions form a Turing-complete instruction set.
- Object model instructions provide an implementation for the Common Type System.
Opcode | Instruction | Description | Type of instruction |
---|---|---|---|
0x58 | add
|
Add two values, returning a new value. | Base instruction |
0xD6 | add.ovf
|
Add signed integer values with overflow check. | Base instruction |
0xD7 | add.ovf.un
|
Add unsigned integer values with overflow check. | Base instruction |
0x5F | and
|
Bitwise AND of two integral values, returns an integral value. | Base instruction |
0xFE 0x00 | arglist
|
Return argument list handle for the current method. | Base instruction |
0x3B | beq <int32 (target)>
|
Branch to target if equal. | Base instruction |
0x2E | beq.s <int8 (target)>
|
Branch to target if equal, short form. | Base instruction |
0x3C | bge <int32 (target)>
|
Branch to target if greater than or equal to. | Base instruction |
0x2F | bge.s <int8 (target)>
|
Branch to target if greater than or equal to, short form. | Base instruction |
0x41 | bge.un <int32 (target)>
|
Branch to target if greater than or equal to (unsigned or unordered). | Base instruction |
0x34 | bge.un.s <int8 (target)>
|
Branch to target if greater than or equal to (unsigned or unordered), short form. | Base instruction |
0x3D | bgt <int32 (target)>
|
Branch to target if greater than. | Base instruction |
0x30 | bgt.s <int8 (target)>
|
Branch to target if greater than, short form. | Base instruction |
0x42 | bgt.un <int32 (target)>
|
Branch to target if greater than (unsigned or unordered). | Base instruction |
0x35 | bgt.un.s <int8 (target)>
|
Branch to target if greater than (unsigned or unordered), short form. | Base instruction |
0x3E | ble <int32 (target)>
|
Branch to target if less than or equal to. | Base instruction |
0x31 | ble.s <int8 (target)>
|
Branch to target if less than or equal to, short form. | Base instruction |
0x43 | ble.un <int32 (target)>
|
Branch to target if less than or equal to (unsigned or unordered). | Base instruction |
0x36 | ble.un.s <int8 (target)>
|
Branch to target if less than or equal to (unsigned or unordered), short form. | Base instruction |
0x3F | blt <int32 (target)>
|
Branch to target if less than. | Base instruction |
0x32 | blt.s <int8 (target)>
|
Branch to target if less than, short form. | Base instruction |
0x44 | blt.un <int32 (target)>
|
Branch to target if less than (unsigned or unordered). | Base instruction |
0x37 | blt.un.s <int8 (target)>
|
Branch to target if less than (unsigned or unordered), short form. | Base instruction |
0x40 | bne.un <int32 (target)>
|
Branch to target if unequal or unordered. | Base instruction |
0x33 | bne.un.s <int8 (target)>
|
Branch to target if unequal or unordered, short form. | Base instruction |
0x8C | box <typeTok>
|
Convert a boxable value to its boxed form. | Object model instruction |
0x38 | br <int32 (target)>
|
Branch to target. | Base instruction |
0x2B | br.s <int8 (target)>
|
Branch to target, short form. | Base instruction |
0x01 | break
|
Inform a debugger that a breakpoint has been reached. | Base instruction |
0x39 | brfalse <int32 (target)>
|
Branch to target if value is zero (false). | Base instruction |
0x2C | brfalse.s <int8 (target)>
|
Branch to target if value is zero (false), short form. | Base instruction |
0x3A | brinst <int32 (target)>
|
Branch to target if value is a non-null object reference (alias for brtrue). | Base instruction |
0x2D | brinst.s <int8 (target)>
|
Branch to target if value is a non-null object reference, short form (alias for brtrue.s). | Base instruction |
0x39 | brnull <int32 (target)>
|
Branch to target if value is null (alias for brfalse). | Base instruction |
0x2C | brnull.s <int8 (target)>
|
Branch to target if value is null (alias for brfalse.s), short form. | Base instruction |
0x3A | brtrue <int32 (target)>
|
Branch to target if value is non-zero (true). | Base instruction |
0x2D | brtrue.s <int8 (target)>
|
Branch to target if value is non-zero (true), short form. | Base instruction |
0x39 | brzero <int32 (target)>
|
Branch to target if value is zero (alias for brfalse). | Base instruction |
0x2C | brzero.s <int8 (target)>
|
Branch to target if value is zero (alias for brfalse.s), short form. | Base instruction |
0x28 | call <method>
|
Call method described by method. | Base instruction |
0x29 | calli <callsitedescr>
|
Call method indicated on the stack with arguments described by callsitedescr. | Base instruction |
0x6F | callvirt <method>
|
Call a method associated with an object. | Object model instruction |
0x74 | castclass <class>
|
Cast obj to class. | Object model instruction |
0xFE 0x01 | ceq
|
Push 1 (of type int32) if value1 equals value2, else push 0. | Base instruction |
0xFE 0x02 | cgt
|
Push 1 (of type int32) if value1 greater that value2, else push 0. | Base instruction |
0xFE 0x03 | cgt.un
|
Push 1 (of type int32) if value1 greater that value2, unsigned or unordered, else push 0. | Base instruction |
0xC3 | ckfinite
|
Throw ArithmeticException if value is not a finite number. | Base instruction |
0xFE 0x04 | clt
|
Push 1 (of type int32) if value1 lower than value2, else push 0. | Base instruction |
0xFE 0x05 | clt.un
|
Push 1 (of type int32) if value1 lower than value2, unsigned or unordered, else push 0. | Base instruction |
0xFE 0x16 | constrained. <thisType>
|
Call a virtual method on a type constrained to be type T. | Prefix to instruction |
0xD3 | conv.i
|
Convert to native int, pushing native int on stack. | Base instruction |
0x67 | conv.i1
|
Convert to int8, pushing int32 on stack. | Base instruction |
0x68 | conv.i2
|
Convert to int16, pushing int32 on stack. | Base instruction |
0x69 | conv.i4
|
Convert to int32, pushing int32 on stack. | Base instruction |
0x6A | conv.i8
|
Convert to int64, pushing int64 on stack. | Base instruction |
0xD4 | conv.ovf.i
|
Convert to a native int (on the stack as native int) and throw an exception on overflow. | Base instruction |
0x8A | conv.ovf.i.un
|
Convert unsigned to a native int (on the stack as native int) and throw an exception on overflow. | Base instruction |
0xB3 | conv.ovf.i1
|
Convert to an int8 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x82 | conv.ovf.i1.un
|
Convert unsigned to an int8 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xB5 | conv.ovf.i2
|
Convert to an int16 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x83 | conv.ovf.i2.un
|
Convert unsigned to an int16 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xB7 | conv.ovf.i4
|
Convert to an int32 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x84 | conv.ovf.i4.un
|
Convert unsigned to an int32 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xB9 | conv.ovf.i8
|
Convert to an int64 (on the stack as int64) and throw an exception on overflow. | Base instruction |
0x85 | conv.ovf.i8.un
|
Convert unsigned to an int64 (on the stack as int64) and throw an exception on overflow. | Base instruction |
0xD5 | conv.ovf.u
|
Convert to a native unsigned int (on the stack as native int) and throw an exception on overflow. | Base instruction |
0x8B | conv.ovf.u.un
|
Convert unsigned to a native unsigned int (on the stack as native int) and throw an exception on overflow. | Base instruction |
0xB4 | conv.ovf.u1
|
Convert to an unsigned int8 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x86 | conv.ovf.u1.un
|
Convert unsigned to an unsigned int8 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xB6 | conv.ovf.u2
|
Convert to an unsigned int16 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x87 | conv.ovf.u2.un
|
Convert unsigned to an unsigned int16 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xB8 | conv.ovf.u4
|
Convert to an unsigned int32 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0x88 | conv.ovf.u4.un
|
Convert unsigned to an unsigned int32 (on the stack as int32) and throw an exception on overflow. | Base instruction |
0xBA | conv.ovf.u8
|
Convert to an unsigned int64 (on the stack as int64) and throw an exception on overflow. | Base instruction |
0x89 | conv.ovf.u8.un
|
Convert unsigned to an unsigned int64 (on the stack as int64) and throw an exception on overflow. | Base instruction |
0x76 | conv.r.un
|
Convert unsigned integer to floating-point, pushing F on stack. | Base instruction |
0x6B | conv.r4
|
Convert to float32, pushing F on stack. | Base instruction |
0x6C | conv.r8
|
Convert to float64, pushing F on stack. | Base instruction |
0xE0 | conv.u
|
Convert to native unsigned int, pushing native int on stack. | Base instruction |
0xD2 | conv.u1
|
Convert to unsigned int8, pushing int32 on stack. | Base instruction |
0xD1 | conv.u2
|
Convert to unsigned int16, pushing int32 on stack. | Base instruction |
0x6D | conv.u4
|
Convert to unsigned int32, pushing int32 on stack. | Base instruction |
0x6E | conv.u8
|
Convert to unsigned int64, pushing int64 on stack. | Base instruction |
0xFE 0x17 | cpblk
|
Copy data from memory to memory. | Base instruction |
0x70 | cpobj <typeTok>
|
Copy a value type from src to dest. | Object model instruction |
0x5B | div
|
Divide two values to return a quotient or floating-point result. | Base instruction |
0x5C | div.un
|
Divide two values, unsigned, returning a quotient. | Base instruction |
0x25 | dup
|
Duplicate the value on the top of the stack. | Base instruction |
0xDC | endfault
|
End fault clause of an exception block. | Base instruction |
0xFE 0x11 | endfilter
|
End an exception handling filter clause. | Base instruction |
0xDC | endfinally
|
End finally clause of an exception block. | Base instruction |
0xFE 0x18 | initblk
|
Set all bytes in a block of memory to a given byte value. | Base instruction |
0xFE 0x15 | initobj <typeTok>
|
Initialize the value at address dest. | Object model instruction |
0x75 | isinst <class>
|
Test if obj is an instance of class, returning null or an instance of that class or interface. | Object model instruction |
0x27 | jmp <method>
|
Exit current method and jump to the specified method. | Base instruction |
0xFE 0x09 | ldarg <uint16 (num)>
|
Load argument numbered num onto the stack. | Base instruction |
0x02 | ldarg.0
|
Load argument 0 onto the stack. | Base instruction |
0x03 | ldarg.1
|
Load argument 1 onto the stack. | Base instruction |
0x04 | ldarg.2
|
Load argument 2 onto the stack. | Base instruction |
0x05 | ldarg.3
|
Load argument 3 onto the stack. | Base instruction |
0x0E | ldarg.s <uint8 (num)>
|
Load argument numbered num onto the stack, short form. | Base instruction |
0xFE 0x0A | ldarga <uint16 (argNum)>
|
Fetch the address of argument argNum. | Base instruction |
0x0F | ldarga.s <uint8 (argNum)>
|
Fetch the address of argument argNum, short form. | Base instruction |
0x20 | ldc.i4 <int32 (num)>
|
Push num of type int32 onto the stack as int32. | Base instruction |
0x16 | ldc.i4.0
|
Push 0 onto the stack as int32. | Base instruction |
0x17 | ldc.i4.1
|
Push 1 onto the stack as int32. | Base instruction |
0x18 | ldc.i4.2
|
Push 2 onto the stack as int32. | Base instruction |
0x19 | ldc.i4.3
|
Push 3 onto the stack as int32. | Base instruction |
0x1A | ldc.i4.4
|
Push 4 onto the stack as int32. | Base instruction |
0x1B | ldc.i4.5
|
Push 5 onto the stack as int32. | Base instruction |
0x1C | ldc.i4.6
|
Push 6 onto the stack as int32. | Base instruction |
0x1D | ldc.i4.7
|
Push 7 onto the stack as int32. | Base instruction |
0x1E | ldc.i4.8
|
Push 8 onto the stack as int32. | Base instruction |
0x15 | ldc.i4.m1
|
Push -1 onto the stack as int32. | Base instruction |
0x15 | ldc.i4.M1
|
Push -1 onto the stack as int32 (alias for ldc.i4.m1). | Base instruction |
0x1F | ldc.i4.s <int8 (num)>
|
Push num onto the stack as int32, short form. | Base instruction |
0x21 | ldc.i8 <int64 (num)>
|
Push num of type int64 onto the stack as int64. | Base instruction |
0x22 | ldc.r4 <float32 (num)>
|
Push num of type float32 onto the stack as F. | Base instruction |
0x23 | ldc.r8 <float64 (num)>
|
Push num of type float64 onto the stack as F. | Base instruction |
0xA3 | ldelem <typeTok>
|
Load the element at index onto the top of the stack. | Object model instruction |
0x97 | ldelem.i
|
Load the element with type native int at index onto the top of the stack as a native int. | Object model instruction |
0x90 | ldelem.i1
|
Load the element with type int8 at index onto the top of the stack as an int32. | Object model instruction |
0x92 | ldelem.i2
|
Load the element with type int16 at index onto the top of the stack as an int32. | Object model instruction |
0x94 | ldelem.i4
|
Load the element with type int32 at index onto the top of the stack as an int32. | Object model instruction |
0x96 | ldelem.i8
|
Load the element with type int64 at index onto the top of the stack as an int64. | Object model instruction |
0x98 | ldelem.r4
|
Load the element with type float32 at index onto the top of the stack as an F. | Object model instruction |
0x99 | ldelem.r8
|
Load the element with type float64 at index onto the top of the stack as an F. | Object model instruction |
0x9A | ldelem.ref
|
Load the element at index onto the top of the stack as an O. The type of the O is the same as the element type of the array pushed on the CIL stack. | Object model instruction |
0x91 | ldelem.u1
|
Load the element with type unsigned int8 at index onto the top of the stack as an int32. | Object model instruction |
0x93 | ldelem.u2
|
Load the element with type unsigned int16 at index onto the top of the stack as an int32. | Object model instruction |
0x95 | ldelem.u4
|
Load the element with type unsigned int32 at index onto the top of the stack as an int32. | Object model instruction |
0x96 | ldelem.u8
|
Load the element with type unsigned int64 at index onto the top of the stack as an int64 (alias for ldelem.i8). | Object model instruction |
0x8F | ldelema <class>
|
Load the address of element at index onto the top of the stack. | Object model instruction |
0x7B | ldfld <field>
|
Push the value of field of object (or value type) obj, onto the stack. | Object model instruction |
0x7C | ldflda <field>
|
Push the address of field of object obj on the stack. | Object model instruction |
0xFE 0x06 | ldftn <method>
|
Push a pointer to a method referenced by method, on the stack. | Base instruction |
0x4D | ldind.i
|
Indirect load value of type native int as native int on the stack. | Base instruction |
0x46 | ldind.i1
|
Indirect load value of type int8 as int32 on the stack. | Base instruction |
0x48 | ldind.i2
|
Indirect load value of type int16 as int32 on the stack. | Base instruction |
0x4A | ldind.i4
|
Indirect load value of type int32 as int32 on the stack. | Base instruction |
0x4C | ldind.i8
|
Indirect load value of type int64 as int64 on the stack. | Base instruction |
0x4E | ldind.r4
|
Indirect load value of type float32 as F on the stack. | Base instruction |
0x4F | ldind.r8
|
Indirect load value of type float64 as F on the stack. | Base instruction |
0x50 | ldind.ref
|
Indirect load value of type object ref as O on the stack. | Base instruction |
0x47 | ldind.u1
|
Indirect load value of type unsigned int8 as int32 on the stack. | Base instruction |
0x49 | ldind.u2
|
Indirect load value of type unsigned int16 as int32 on the stack. | Base instruction |
0x4B | ldind.u4
|
Indirect load value of type unsigned int32 as int32 on the stack. | Base instruction |
0x4C | ldind.u8
|
Indirect load value of type unsigned int64 as int64 on the stack (alias for ldind.i8). | Base instruction |
0x8E | ldlen
|
Push the length (of type native unsigned int) of array on the stack. | Object model instruction |
0xFE 0x0C | ldloc <uint16 (indx)>
|
Load local variable of index indx onto stack. | Base instruction |
0x06 | ldloc.0
|
Load local variable 0 onto stack. | Base instruction |
0x07 | ldloc.1
|
Load local variable 1 onto stack. | Base instruction |
0x08 | ldloc.2
|
Load local variable 2 onto stack. | Base instruction |
0x09 | ldloc.3
|
Load local variable 3 onto stack. | Base instruction |
0x11 | ldloc.s <uint8 (indx)>
|
Load local variable of index indx onto stack, short form. | Base instruction |
0xFE 0x0D | ldloca <uint16 (indx)>
|
Load address of local variable with index indx. | Base instruction |
0x12 | ldloca.s <uint8 (indx)>
|
Load address of local variable with index indx, short form. | Base instruction |
0x14 | ldnull
|
Push a null reference on the stack. | Base instruction |
0x71 | ldobj <typeTok>
|
Copy the value stored at address src to the stack. | Object model instruction |
0x7E | ldsfld <field>
|
Push the value of the static field on the stack. | Object model instruction |
0x7F | ldsflda <field>
|
Push the address of the static field, field, on the stack. | Object model instruction |
0x72 | ldstr <string>
|
Push a string object for the literal string. | Object model instruction |
0xD0 | ldtoken <token>
|
Convert metadata token to its runtime representation. | Object model instruction |
0xFE 0x07 | ldvirtftn <method>
|
Push address of virtual method on the stack. | Object model instruction |
0xDD | leave <int32 (target)>
|
Exit a protected region of code. | Base instruction |
0xDE | leave.s <int8 (target)>
|
Exit a protected region of code, short form. | Base instruction |
0xFE 0x0F | localloc
|
Allocate space from the local memory pool. | Base instruction |
0xC6 | mkrefany <class>
|
Push a typed reference to ptr of type class onto the stack. | Object model instruction |
0x5A | mul
|
Multiply values. | Base instruction |
0xD8 | mul.ovf
|
Multiply signed integer values. Signed result shall fit in same size. | Base instruction |
0xD9 | mul.ovf.un
|
Multiply unsigned integer values. Unsigned result shall fit in same size. | Base instruction |
0x65 | neg
|
Negate value. | Base instruction |
0x8D | newarr <etype>
|
Create a new array with elements of type etype. | Object model instruction |
0x73 | newobj <ctor>
|
Allocate an uninitialized object or value type and call ctor. | Object model instruction |
0xFE 0x19 | no. { typecheck, rangecheck, nullcheck } |
The specified fault check(s) normally performed as part of the execution of the subsequent instruction can/shall be skipped. | Prefix to instruction |
0x00 | nop
|
Do nothing (No operation). | Base instruction |
0x66 | not
|
Bitwise complement. | Base instruction |
0x60 | or
|
Bitwise OR of two integer values, returns an integer. | Base instruction |
0x26 | pop
|
Pop value from the stack. | Base instruction |
0xFE 0x1E | readonly.
|
Specify that the subsequent array address operation performs no type check at runtime, and that it returns a controlled-mutability managed pointer. | Prefix to instruction |
0xFE 0x1D | refanytype
|
Push the type token stored in a typed reference. | Object model instruction |
0xC2 | refanyval <type>
|
Push the address stored in a typed reference. | Object model instruction |
0x5D | rem
|
Remainder when dividing one value by another. | Base instruction |
0x5E | rem.un
|
Remainder when dividing one unsigned value by another. | Base instruction |
0x2A | ret
|
Return from method, possibly with a value. | Base instruction |
0xFE 0x1A | rethrow
|
Rethrow the current exception. | Object model instruction |
0x62 | shl
|
Shift an integer left (shifting in zeros), return an integer. | Base instruction |
0x63 | shr
|
Shift an integer right (shift in sign), return an integer. | Base instruction |
0x64 | shr.un
|
Shift an integer right (shift in zero), return an integer. | Base instruction |
0xFE 0x1C | sizeof <typeTok>
|
Push the size, in bytes, of a type as an unsigned int32. | Object model instruction |
0xFE 0x0B | starg <uint16 (num)>
|
Store value to the argument numbered num. | Base instruction |
0x10 | starg.s <uint8 (num)>
|
Store value to the argument numbered num, short form. | Base instruction |
0xA4 | stelem <typeTok>
|
Replace array element at index with the value on the stack. | Object model instruction |
0x9B | stelem.i
|
Replace array element at index with the native int value on the stack. | Object model instruction |
0x9C | stelem.i1
|
Replace array element at index with the int8 value on the stack. | Object model instruction |
0x9D | stelem.i2
|
Replace array element at index with the int16 value on the stack. | Object model instruction |
0x9E | stelem.i4
|
Replace array element at index with the int32 value on the stack. | Object model instruction |
0x9F | stelem.i8
|
Replace array element at index with the int64 value on the stack. | Object model instruction |
0xA0 | stelem.r4
|
Replace array element at index with the float32 value on the stack. | Object model instruction |
0xA1 | stelem.r8
|
Replace array element at index with the float64 value on the stack. | Object model instruction |
0xA2 | stelem.ref
|
Replace array element at index with the ref value on the stack. | Object model instruction |
0x7D | stfld <field>
|
Replace the value of field of the object obj with value. | Object model instruction |
0xDF | stind.i
|
Store value of type native int into memory at address. | Base instruction |
0x52 | stind.i1
|
Store value of type int8 into memory at address. | Base instruction |
0x53 | stind.i2
|
Store value of type int16 into memory at address. | Base instruction |
0x54 | stind.i4
|
Store value of type int32 into memory at address. | Base instruction |
0x55 | stind.i8
|
Store value of type int64 into memory at address. | Base instruction |
0x56 | stind.r4
|
Store value of type float32 into memory at address. | Base instruction |
0x57 | stind.r8
|
Store value of type float64 into memory at address. | Base instruction |
0x51 | stind.ref
|
Store value of type object ref (type O) into memory at address. | Base instruction |
0xFE 0x0E | stloc <uint16 (indx)>
|
Pop a value from stack into local variable indx. | Base instruction |
0x0A | stloc.0
|
Pop a value from stack into local variable 0. | Base instruction |
0x0B | stloc.1
|
Pop a value from stack into local variable 1. | Base instruction |
0x0C | stloc.2
|
Pop a value from stack into local variable 2. | Base instruction |
0x0D | stloc.3
|
Pop a value from stack into local variable 3. | Base instruction |
0x13 | stloc.s <uint8 (indx)>
|
Pop a value from stack into local variable indx, short form. | Base instruction |
0x81 | stobj <typeTok>
|
Store a value of type typeTok at an address. | Object model instruction |
0x80 | stsfld <field>
|
Replace the value of the static field with val. | Object model instruction |
0x59 | sub
|
Subtract value2 from value1, returning a new value. | Base instruction |
0xDA | sub.ovf
|
Subtract native int from a native int. Signed result shall fit in same size. | Base instruction |
0xDB | sub.ovf.un
|
Subtract native unsigned int from a native unsigned int. Unsigned result shall fit in same size. | Base instruction |
0x45 | switch <uint32, int32, int32 (t1..tN)>
|
Jump to one of n values. | Base instruction |
0xFE 0x14 | tail.
|
Subsequent call terminates current method. | Prefix to instruction |
0x7A | throw
|
Throw an exception. | Object model instruction |
0xFE 0x12 | unaligned. (alignment)
|
Subsequent pointer instruction might be unaligned. | Prefix to instruction |
0x79 | unbox <valuetype>
|
Extract a value-type from obj, its boxed representation, and push a controlled-mutability managed pointer to it to the top of the stack. | Object model instruction |
0xA5 | unbox.any <typeTok>
|
Extract a value-type from obj, its boxed representation, and copy to the top of the stack. | Object model instruction |
0xFE 0x13 | volatile.
|
Subsequent pointer reference is volatile. | Prefix to instruction |
0x61 | xor
|
Bitwise XOR of integer values, returns an integer. | Base instruction |
See also
[edit]- Common Intermediate Language is the assembly language that uses the instruction set.
- Common Language Infrastructure is the standard in which the Common Intermediate Language is defined.
- .NET Framework is a platform and implementation of the Common Language Infrastructure.
- Mono is a cross-platform open-source implementation of the Common Language Infrastructure.