Chapter 11: Code Generation for a Virtual Machine
In this chapter, we take a final step in program translation by
traversing an AST and generating a form of code that is suitable
for a virtual machine
The construction of an AST
and its subsequent semantic processing
(Chapter 8 and
developed all of the information that is necessary to translate a
source program into some form of interpretable or executable code.
The AST serves well for expressing the structure and the meaning of
a source program. However, its design is purposefully abstract, and
thus independent of any particular architecture specification.
Moreover, the AST nicely represents the nested structure of programs
written in a modern programming language, while the instructions
executed by most architectures are more linear in nature.
Chapter 5 and
parsing techniques are presented that check an
input program's syntax based on a programming language's grammar.
While the grammar provides an automatic structure for regulating the
parser's activity, the translation of the source program into a
suitable AST requires actions that are inserted by hand. In this
chapter, code generation is essentially the inverse of the parsing
process. A program's AST provides a structure that can be
traversed automatically, but the actions required to synthesize code
are formulated by hand.