Interprocedural optimization

Interprocedural optimization (IPO) is a collection of <a href="/facts/Compiler/WNfCDFJe">compiler</a> techniques used in <a href="/facts/Computer_programming/QmSsFnu0">computer programming</a> to improve performance in programs containing many frequently used <a href="/facts/Function_(computer_science)/9vFJrg0A">functions</a> of small or medium length. IPO differs from other <a href="/facts/Compiler_optimizations/JXnv4LUd">compiler optimizations</a> by analyzing the entire program as opposed to a single function or block of code.
IPO seeks to reduce or eliminate duplicate calculations and inefficient use of memory and to simplify iterative sequences such as loops. If a call to another routine occurs within a loop, IPO analysis may determine that it is best to <a href="/facts/Inline_expansion/jhQsJwLX">inline</a> that routine. Additionally, IPO may re-order the routines for better memory layout and <a href="/facts/Memory_locality/fYFKDv5q">locality</a>.
IPO may also include typical compiler optimizations applied on a whole-program level, for example, <a href="/facts/Dead_code_elimination/waQRsajr">dead code elimination</a> (DCE), which removes code that is never executed. IPO also tries to ensure better use of constants. Modern compilers offer IPO as an option at compile-time. The actual IPO process may occur at any step between the human-readable source code and producing a finished executable binary program.
For languages that compile on a file-by-file basis, effective IPO across <a href="/facts/Translation_unit_(programming)/7GbSbEYL">translation units</a> (module files) requires knowledge of the "entry points" of the program so that a whole program optimization (WPO) can be run. In many cases, this is implemented as a link-time optimization (LTO) pass, because the whole program is visible to the linker.

Interprocedural optimization open-in-new

Interprocedural optimization