What is lto?

LTO, short for Link-Time Optimization, is a compiler optimization technique that allows the compiler to optimize code across multiple compilation units (e.g., .c or .cpp files). Traditionally, compilers optimize each file independently, but LTO enables the compiler to see the entire program during the linking phase, allowing for more aggressive and effective optimizations.

Here's a breakdown of key aspects:

• Interprocedural Optimization: LTO facilitates interprocedural%20optimization, enabling optimizations that span function boundaries. This is impossible when compiling each file separately.

• Dead Code Elimination: With a global view, LTO can more easily identify and remove dead%20code (code that is never executed).

• Function Inlining: LTO can perform more aggressive function%20inlining, replacing function calls with the actual function code, reducing overhead and potentially enabling further optimizations.

• Cross-File Optimization: LTO allows the compiler to optimize code across file boundaries, leading to improvements in areas such as code size, performance, and power consumption.

• Compiler Support: Popular compilers like GCC and Clang support LTO. It typically involves passing a specific flag during both compilation and linking stages (e.g., -flto in GCC/Clang).

• Trade-offs: While LTO can improve performance, it can also increase compile%20time and memory usage during the build process.