Literal pool
Encyclopedia
In computer science
, and specifically in compiler
and assembler design, a literal pool is a lookup table
used to hold literal
s during assembly and execution
.
Multiple (local) literal pools are typically used only for computer architecture
s that lack branch instructions for long jumps, or have a set of instructions optimized for shorter jumps. Examples of such architectures include ARM architecture
and the IBM System/360 and later architectures, which had a number of instructions which took 12-bit address offsets. In this case, the compiler would create a literal table on every 4K page; any branches whose target was less than 4K bytes away could be taken immediately; longer branches required an address lookup via the literal table. The entries in the literal pool are placed into the object
relocation table during assembly, and are then resolved at link edit time.
In certain ways, a literal pool resembles a TOC or a global offset table (GOT), except that the implementation is considerably simpler, and there may be multiple literal tables per object.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, and specifically in compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
and assembler design, a literal pool is a lookup table
Lookup table
In computer science, a lookup table is a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation. The savings in terms of processing time can be significant, since retrieving a value from memory is often faster than...
used to hold literal
Literal
Literal may refer to:*Literal and figurative language, taken in a non-figurative sense*Literal translation, the close adherence to the forms of a source language text...
s during assembly and execution
Execution (computers)
Execution in computer and software engineering is the process by which a computer or a virtual machine carries out the instructions of a computer program. The instructions in the program trigger sequences of simple actions on the executing machine...
.
Multiple (local) literal pools are typically used only for computer architecture
Computer architecture
In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....
s that lack branch instructions for long jumps, or have a set of instructions optimized for shorter jumps. Examples of such architectures include ARM architecture
ARM architecture
ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
and the IBM System/360 and later architectures, which had a number of instructions which took 12-bit address offsets. In this case, the compiler would create a literal table on every 4K page; any branches whose target was less than 4K bytes away could be taken immediately; longer branches required an address lookup via the literal table. The entries in the literal pool are placed into the object
Object code
Object code, or sometimes object module, is what a computer compiler produces. In a general sense object code is a sequence of statements in a computer language, usually a machine code language....
relocation table during assembly, and are then resolved at link edit time.
In certain ways, a literal pool resembles a TOC or a global offset table (GOT), except that the implementation is considerably simpler, and there may be multiple literal tables per object.