llvm-extract - extract a function from an LLVM module — LLVM 17.0.6 documentation

# llvm-extract - extract a function from an LLVM module

## SYNOPSIS

llvm-extract [options] –func function-name [filename]

## DESCRIPTION

The llvm-extract command takes the name of a function and extracts it from the specified LLVM bitcode file. It is primarily used as a debugging tool to reduce test cases from larger programs that are triggering a bug.

In addition to extracting the bitcode of the specified function, llvm-extract will also remove unreachable global variables, prototypes, and unused types.

The llvm-extract command reads its input from standard input if filename is omitted or if filename is `-`. The output is always written to standard output, unless the -o option is specified (see below).

## OPTIONS

–alias alias-name

> Extract the alias named function-name from the LLVM bitcode. May be specified multiple times to extract multiple alias at once.

–ralias alias-regular-expr

> Extract the alias matching alias-regular-expr from the LLVM bitcode. All alias matching the regular expression will be extracted. May be specified multiple times.

–bb basic-block-specifier

> Extract basic blocks(s) specified in basic-block-specifier. May be specified multiple times. Each <function:bb[;bb]> specifier pair will create a function. If multiple basic blocks are specified in one pair, the first block in the sequence should dominate the rest.

–delete

> Delete specified Globals from Module.

-f

> Enable binary output on terminals. Normally, llvm-extract will refuse to write raw bitcode output if the output stream is a terminal. With this option, llvm-extract will write raw bitcode regardless of the output device.

–func function-name

> Extract the function named function-name from the LLVM bitcode. May be specified multiple times to extract multiple functions at once.

–rfunc function-regular-expr

> Extract the function(s) matching function-regular-expr from the LLVM bitcode. All functions matching the regular expression will be extracted. May be specified multiple times.

–glob global-name

> Extract the global variable named global-name from the LLVM bitcode. May be specified multiple times to extract multiple global variables at once.

–rglob glob-regular-expr

> Extract the global variable(s) matching global-regular-expr from the LLVM bitcode. All global variables matching the regular expression will be extracted. May be specified multiple times.

–keep-const-init

> Preserve the values of constant globals.

–recursive

> Recursively extract all called functions

-help

> Print a summary of command line options.

-o filename

> Specify the output filename. If filename is “-” (the default), then llvm-extract sends its output to standard output.

-S

> Write output in LLVM intermediate language (instead of bitcode).

## EXIT STATUS

If llvm-extract succeeds, it will exit with 0. Otherwise, if an error occurs, it will exit with a non-zero value.

## SEE ALSO

bugpoint(1)