Intermediate code generation in compiler design example

Intermediate code generation in compiler design example generator#
Intermediate code generation in compiler design example full#
Intermediate code generation in compiler design example portable#

An IR may take one of several forms: an in-memory data structure, or a special tuple- or stack-based code readable by the program.

A 'good' IR must be accurate вЂ“ capable of representing the source code without loss of information вЂ“ and independent of any particular source or target language. An IR is designed to be conducive for further processing, such as optimization and translation. An intermediate representation ( IR) is the data structure or code used internally by a compiler or virtual machine to represent source code. Thus, the following tuples are sufficient: So we only need tuples for the core language.

Language is small nearly everything interesting (like I/O) is in a library.

Arrays arenвЂ™t copied element by element: array assignment is just an assignment of the starting address.

Block structure is very restricted: all functions on same level (no nesting) variables are either truly global or local to a top-level function implementation drastically simplified because no static links are ever needed and functions can be easily passed as parameters without scoping trouble.

All parameters passed by value, and in order.

No true arrays - e1 just abbreviates *(e1+e2) all indicies start at zero, thereвЂ™s no bounds checking.

Only base types are several varieties of ints and floats.

Why? C is such a simple language, an IR is fairly easy to design. LetвЂ™s design our own tuple-based IR for C. (func $func0 (param $var0 i32) (param $var1 i32) (result i32) (2) the instruction before the target of a branch. (2) the instruction after a conditional branch

Starts with: (1) target of a branch (label) or.

To locate basic blocks in flattened code: in the abscence of hardware faults, interrupts, crashes, threading problems, etc.

maximal-length code block with only one entry and one exit.

maximal-length straight-line code block.

maximal-length sequence of instructions that will execute in its entirety.

Some structures generally associated with IRs include:ДЄ control flow graph is a graph whose nodes are basic blocks and whose edges are transitions between blocks. TheyвЂ™re not changed in this loop, so we neednвЂ™t save them at the end. Variable $j$ can go in r1 and $n$ in r2 and $di$ in r3. Suppose in our example we know the target is a RISC processor with no memory operations.

For architecture dependent optimizations.

Intimiately concerned with run-time storage management issues like stack frames and paramater passing mechanisms.

Deviates from target language only in its inclusion of pseudo-operations and symbolic (virtual) registers.

Extremely close to machine architecture.

Some languages will require bounds checking on arrays and a different treatment of for-loops. Assume here that doubles require 8 bytes and ints require 4 bytes:

Intermediate code generation in compiler design example generator#

When constructing a medium level IR, the IR generator must be told about the sizes of source language datatypes. Great for architecture-independent optimizations.Break down data structure references to deal only with simple ints and floats.Tuples are stored as on the left column, but usually rendered as on the right. WeвЂ™ll use a running example code fragment to illustrate various options. Flat, tuple-based, generally three-address code (quadruples).Intermediate representations are usually: To perform machine independent optimizations.(Though this might be a bit of an exaggeration in practice!)

Intermediate code generation in compiler design example full#

We only have to write $2n$ half-compilers instead of $n(n-1)$ full compilers.

We can build a new front-end for an existing back end (so a new machine can quickly get a set of compilers for different source languages).

Intermediate code generation in compiler design example portable#

We can build new back ends for an existing front end (making the source language more portable across machines).

To break the difficult problem of translation into two simpler, more manageable pieces.

Because translation appears to inherently require analysis and synthesis.

We use intermediate representations for at least four reasons: A good IR is one that is fairly independent of the source and target languages, so that it maximizes its ability to be used in a retargetable compiler. What is an IR?ДЄn intermediate representation is a representation of a program вЂњbetweenвЂќ the source and target languages. You canвЂ™t really write a translator, or even an iterpreter, for a complex language, without using an intermediate representation.