編譯原理概述ppt課件-文庫(kù)吧資料
2024-12-14 05:40本頁(yè)面
【正文】 ase of pilation. ? Error reported by a piler are static (or piletime) errors. ? It is important to generate meaningful error messages. ? Error handler contains different operations for a specific piler phase and situation Compiler Language ? The implementation (or host) language has to be machine language. – This was how the first pilers were written. ? Another approach is to write the piler in another language for which a piler already exists. – We need only to pile the new piler using the existing piler to get a running program. ? What if the existing piler runs on a machine different from the target machine? – Compilation produces a cross piler – a piler that generates target code for a different machine. TDiagram ? A piler written in language H (host language) that translates language S (source language) into language T (target language) is drawn as the following Tdiagram: ? This is equivalent to saying that the piler runs on “machine” H. ? Typically, we expect H = T. – the piler produces code for the same machine as the one on which it runs. S T H Case 1 ? There are two pilers that run on the same machine H. – One translates from language A to language B. – The other translates from language B to language C. ? We can bine them by letting the output of the first to be the input to the second. ? The result is a piler from A to C on machine H. A B H B C H A C H = Case 2 ? We can use a piler M from “machine” H to “machine” K to translate the implementation language of another piler from H to K. A B H H K M A B K = Existing Language ? Given: – Machine H – Compiler for a language B written in H that translates B to H. ? Wanted: – To get a piler on machine H that translates a language A to H ? We can write a piler for A using language B. A H B B H H A H H = Cross Compiler ? Given : – Machine K. (K is a host language here.) – A piler for a language B written in K that translates B to K. ? Wanted: – To get a piler for a language A. The target machine is H. A H B B K K A H K = H = S ? ? Can a piler be written in the same language that it is to pile? ? No piler for the source language exists, so the piler itself cannot be piled. ? There is a circulatory problem here. S T S Bootstrapping 1. Write a “quick and dirty” piler in assembly language. 2. Use this piler to pile the “good” piler. 3. Repile the “good” piler to produce a final version. A H A A H H A H H = A H A A H H A H H = Quick and dirty Inefficient piler Inefficient piler Final version Compiler in its own language Porting to New Host A K A A H H A K H = A K A A K H A H H = Original piler Cross piler Retargeted piler Compiler in its own language Compiler in its own language Cross piler How to Study It ? 1 Pay much attention to conceptions ? 2 Pay much attention to the examples to introduce ? a new algorithm ? 3 Do much homework/ Follow examples by hand by yourself to fully understand abstract algorithm ? 4 Carefully read textbook and follow lecture ? ( Apply Intensive Reading Skill to
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