Methods to Optimize Code Size

This section provides some guidance on how to achieve smaller object and smaller executable size when using the optimizing features of Intel compilers.

To begin, there are two compiler options that are designed to prioritize code size over performance:

Favors size over speed

Linux* and macOS*: -Os

Windows*: /Os

This option enables optimizations that do not increase code size; it produces smaller code size than option O2.

Option Os disables some optimizations that may increase code size for a small speed benefit.

Minimizes code size

Linux* and macOS*: -O1

Windows*: /O1

Compared to option Os, option O1 disables even more optimizations that are generally known to increase code size. Specifying option O1 implies option Os.

As an intermediate step in reducing code size, you can replace option O3 with option O2 before specifying option O1.

Option O1 may improve performance for applications with very large code size, many branches, and execution time not dominated by code within loops.

For more information about the above options, see their full descriptions in the Compiler Reference.

The rest of this section briefly discusses methods that may help you further improve code size even when compared to the default behaviors of options Os and O1.

The following table shows the methods for code size optimization that are summarized in this section.

Disable or Decrease the Amount of Inlining

Strip Symbols from Your Binaries

Dynamically Link Intel-Provided Libraries

Disable Inline Expansion of Standard Library or Intrinsic Functions

Disable Passing Arguments in Registers Instead of On the Stack

Disable Loop Unrolling

Disable Automatic Vectorization

Avoid Unnecessary 16-Byte Alignment

Use Inter-Procedural Optimization (IPO)

For more information about compiler options that are mentioned in the above topics, see their full descriptions in the Compiler Reference.

Things to remember:

See Also