Editing Three-address code (section)

{{Short description|Intermediate code used by optimizing compilers}}
In [[computer science]], '''three-address code'''<ref>{{Cite book|url=https://archive.org/details/compilersprincip00ahoa/page/466|title=Compilers, principles, techniques, and tools|last=V.|first=Aho, Alfred|date=1986|publisher=Addison-Wesley Pub. Co|others=Sethi, Ravi., Ullman, Jeffrey D., 1942-|isbn=0201100886|location=Reading, Mass.|pages=[https://archive.org/details/compilersprincip00ahoa/page/466 466]|oclc=12285707|url-access=registration}}</ref> (often abbreviated to TAC or 3AC) is an [[intermediate language|intermediate code]] used by [[optimizing compiler]]s to aid in the implementation of [[code-improving transformation]]s. Each TAC instruction has at most three operands and is typically a combination of assignment and a binary operator. For example, <code>t1 := t2 + t3</code>. The name derives from the use of three operands in these statements even though instructions with fewer operands may occur.

Since three-address code is used as an intermediate language within compilers, the operands will most likely not be concrete memory addresses or [[processor registers]], but rather symbolic addresses that will be translated into actual addresses during [[register allocation]]. It is also not uncommon that operand names are numbered sequentially since three-address code is typically generated by the compiler.

A refinement of three-address code is [[A-normal form]] (ANF).