Extended basic block explained

In computing, an extended basic block^{[1] [2]} is a collection of basic blocks of the code within a program with certain properties that make them highly amenable to optimizations. Many compiler optimizations operate on extended basic blocks.

Definition

An extended basic block is a maximal collection of basic blocks where:

• only the first basic block can have multiple predecessor basic blocks;
• all the other basic blocks have one single predecessor basic block, which must be within the collection of basic blocks.

Uses

Many local optimizations that operate on basic blocks can be easily extended to operate on extended basic blocks. An example is common subexpression elimination which removes duplicate expressions. In its simplest form it is a local optimization, operating only on basic blocks.^[3]

See also

• Basic block
• Control-flow graph
• Tracing just-in-time compilation

External links

• Basic Blocks - GNU Compiler Collection
• The Difference Between Extended Basic Blocks and Traces

Notes and References

1. Cooper, Keith D., and Torczon, Linda, Engineering a Compiler, Morgan Kaufmann, 2004, page 405
2. Steven S. Muchnick Advanced Compiler Design and Implementation, Morgan Kaufmann Publishers, 1997. page 175
3. Web site: Extending Value Numbering - ReuvenLax - Site Home - MSDN Blogs . 2012-07-04 . dead . https://web.archive.org/web/20140515102346/http://blogs.msdn.com/b/reuvenlax/archive/2005/12/15/504202.aspx . 2014-05-15 .