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Passes of compilers
There are two types of compiler passes: multi-pass compilers perform multiple traversals of the source code to perform different stages of compilation like scanning, parsing, semantic analysis, etc. One-pass compilers only traverse the source code once, performing all compilation stages on each line before moving to the next. Bootstrapping is the process of using a compiler written in a language to compile itself, allowing the creation of a self-hosting compiler for that language. It involves first creating a simple bootstrap compiler for a language subset, then using that to compile a full compiler for the language which can then compile future versions.
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Passes of compilers
- 1. Compiler Passes 1 • Passis a complete traversal of the source program. • Compiler has two passes to traverse the source program. – Multi-pass Compiler – One-pass Compiler
- 2. Multi-pass Compiler 2 • Multipass compiler is used to process the source code of a program several times. • In the first pass, compiler can read the source program, scan it, extract the tokens and store the result in an output file. • In the second pass, compiler can read the output file produced by first pass, build the syntactic tree and perform the syntactical analysis. The output of this phase is a file that contains the syntactical tree. • In the third pass, compiler can read the output file produced by second pass and check that the tree follows the rules of language or not. The output of semantic analysis phase is the annotated tree syntax. • This pass is going on, until the target output is produced.
- 3. One-pass Compiler 3 • One-passcompiler is used to traverse the program only once. The one-pass compiler passes only once through the parts of each compilation unit. It translates each part into its final machine code. • In the one pass compiler, when the line source is processed, it is scanned and the token is extracted. • Then the syntax of each line is analyzed and the tree structure is build. After the semantic part, the code is generated. • The same process is repeated for each line of code until the entire program is compiled.
- 4. Bootstrapping 4 •Bootstrapping is widelyused in the compilation development. •Bootstrapping is used to produce a self-hosting compiler. Self-hosting compiler is a type of compiler that can compile its own source code. •Bootstrap compiler is used to compile the compiler and then you can use this compiled compiler to compile everything else as well as future versions of itself. A compiler can be characterized by three languages: 1.Source Language 2.Target Language 3.Implementation Language
- 5. Implementing a Bootstrapcompiler 5 •Compilers are of two kinds 1. Native Compiler 2. Cross Compiler •Native Compiler: Native compilers are written in the same language as the target language. •E.g. SMM is a compiler for the language S that is in a language that runs on machine M and generates output code that runs on machine M.
- 6. Implementing a Bootstrapcompiler 6 •Follow some steps to produce a new language L for machine A: 1.Create a compiler S CA A for subset, S of the desired language, L using language "A" and that compiler runs on machine A. 2.Create a compiler L CS A for language L written in a subset of L. 3. Compile L CS A using the compiler S CA A to obtain L CA A . L CA A is a compiler for language L, which runs on machine A and produces code for machine A.
- 7. Implementing a Bootstrapcompiler 7 Cross Compiler: Cross compilers are written in different language as the target language. •E.g. SNM is a compiler for the language S that is in a language that runs on machine N and generates output code that runs on machine M. Steps involving to produce a compiler for a different machine B (or cross compiler): 1. Convert in to ( by hand, if necessary). Recall that language S is a subset of language L. 2. Compile to produce , a cross-compiler for L which runs on machine A and produces code for machine B. 3. Compile with the cross-compiler to produce , a compiler for language L which runs on machine B
- 8. Implementing a Bootstrapcompiler 8
Editor's Notes
- #2 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #3 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #4 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #5 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #6 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #7 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #8 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.
- #9 Example : If you write a program in C, you lose the ability you had in assembly language to specify register allocation; if you write in Prolog, you lose the ability you had in C to specify arbitrary linked structures using pointers. There is a natural tension between striving for the concise, clear and reliable expression of a computation in a high-level abstraction, and wanting the flexibility of specifying the computation in detail. An abstraction can never be as exact or optimal as a low level specification.