1. T-diagrams “Mommy, where do compilers come from?” Adapted from: http://www.cse.buffalo.edu/~drpierce/cse/443S2005/lectures/T-diagrams.ppt

2. T-diagrams Different diagrams for different kinds of programs Visual explanation of interactions involving compilers and interpreters

3. Programs Program P written in language L Example: Sort program written in Java L P Java sort

4. Machines Machine executing language M Example: Sun workstation executing SPARC machine code Msparc

5. Executing Programs Program implementation language must match machine sparc sort sparc

6. Interpreters Interpreter executing language L written in language M Example: Lisp interpreter running on sparc L M Lisp sparc

7. Interpreting Programs Interpreter mediates between programming language and machine language Lisp sort sparc Lisp sparc

8. Virtual Machines Interpreter creates a “virtual machine” Lisp sort sparc Lisp sparcLisp sort Lisp

9. Compilers Compiler translating from source language S to target language T implemented in M Example: C compiler for sparc platform ST M C  sparc -->

10. Compiling Programs Compiler inputs program in source language, outputs in target language C sort C  sparc sort sparc sort sparc

11. Compiler Correctness Compiled target program has the same meaning as the source program sparc sort sparc C sort C ==

12. Java Programming Environment Javac : Java to Java byte code (JBC) compiler Java : Java Virtual Machine byte code interpreter Java  JBC MJava P JBC P P M M M “javac”“java”

13. Where Do Compilers Come From? 1. Write it in machine code L  M M A lot of work

14. Where Do Compilers Come From? 1. Write it in machine code 2. Write it in a lower level language and compile it using an existing compiler L  M C C M M L M M But where did the C compiler come from?

15. Where Do Compilers Come From? 1. Write it in machine code 2. Write it in a lower level language and compile it using an existing compiler 3. Write it in the same language that it compiles and bootstrap L  M L

16. Bootstrapping a Compiler Write the compiler in its own language (#0) Write a simple native compiler (#1) Use compiler #1 to compile #0 to get native compiler with more frills (#2) Repeat as desired

17. Bootstrapping a Compiler L  M L L --> M M L  M M #0 (the real thing) #1 (simple) #2 (real thing compiled)

18. Bootstrapping a Compiler, Stage 2 L  M L L M M L M M #0 (the real thing) #2 (the real thing compiled) #3 (compiled with the real thing) Consistency test: #2 = #3 literally

19. Porting a Compiler 1. Rewrite back end to target new machine 1. Compile on new machine L  M C L N C

20. Porting a Compiler 1. Rewrite back end to target new machine 1. Compile on new machine L  N C C N N L N N

21. Porting a Compiler II Rewrite back end to target new machine Compile using native compiler L  N L L M M L N M “cross compiler”

22. Cross Compilers A cross compiler compiles to a target language different from the language of the machine it runs on

23. Porting a Compiler II Rewrite back end to target new machine Compile using native compiler Recompile using cross compiler L  N L L N M L N N