Flang command line argument reference¶

Introduction ¶

-dumpmachine¶

Display the compiler’s target processor

-dumpversion¶

Display the version of the compiler

-fopenmp-targets=<arg1>,<arg2>...¶

Specify comma-separated list of triples OpenMP offloading targets to be supported

-fppc-native-vector-element-order, -fno-ppc-native-vector-element-order¶

Specifies PowerPC native vector element order (default)

-frtlib-add-rpath, -fno-rtlib-add-rpath¶

Add -rpath with architecture-specific resource directory to the linker flags. When –hip-link is specified, also add -rpath with HIP runtime library directory to the linker flags

-fstack-arrays, -fno-stack-arrays¶

Attempt to allocate array temporaries on the stack, no matter their size

-fversion-loops-for-stride, -fno-version-loops-for-stride¶

Create unit-strided versions of loops

--gcc-install-dir=<arg>¶

Use GCC installation in the specified directory. The directory ends with path components like ‘lib{,32,64}/gcc{,-cross}/$triple/$version’. Note: executables (e.g. ld) used by the compiler are not overridden by the selected GCC installation

--gcc-toolchain=<arg>¶

Specify a directory where Flang can find ‘lib{,32,64}/gcc{,-cross}/$triple/$version’. Flang will use the GCC installation with the largest version

-gpulibc¶

Link the LLVM C Library for GPUs

-help, --help¶

Display available options

--help-hidden¶

Display help for hidden options

-mllvm <arg>, -mllvm=<arg>¶

Additional arguments to forward to LLVM’s option processing

-mmlir <arg>¶

Additional arguments to forward to MLIR’s option processing

-module-dir<dir>, -J<arg>¶

This option specifies where to put .mod files for compiled modules. It is also added to the list of directories to be searched by an USE statement. The default is the current directory.

-nogpulib¶

Do not link device library for CUDA/HIP device compilation

-nogpulibc¶

-nopie¶

-o<file>¶

Write output to <file>

-print-effective-triple, --print-effective-triple¶

Print the effective target triple

-print-target-triple, --print-target-triple¶

Print the normalized target triple

-pthread, -no-pthread¶

Support POSIX threads in generated code

-save-temps=<arg>, --save-temps=<arg>, -save-temps (equivalent to -save-temps=cwd), --save-temps (equivalent to -save-temps=cwd)¶

Save intermediate compilation results. <arg> can be set to ‘cwd’ for current working directory, or ‘obj’ which will save temporary files in the same directory as the final output file

--sysroot=<arg>¶

--target=<arg>, -target <arg>¶

Generate code for the given target

-v¶

Show commands to run and use verbose output

--version¶

Print version information

-x<language>¶

Treat subsequent input files as having type <language>

Actions ¶

The action to perform on the input.

-E¶

Only run the preprocessor

-S¶

Only run preprocess and compilation steps

-c¶

Only run preprocess, compile, and assemble steps

-emit-llvm¶

Use the LLVM representation for assembler and object files

-fsyntax-only¶

Run the preprocessor, parser and semantic analysis stages

Compilation options ¶

Flags controlling the behavior of Flang during compilation. These flags have no effect during actions that do not perform compilation.

-Xflang <arg>¶

Pass <arg> to the flang compiler

-moutline-atomics, -mno-outline-atomics¶

Generate local calls to out-of-line atomic operations

-std=<arg>, --std=<arg>¶

Language standard to compile for

Preprocessor options ¶

Flags controlling the behavior of the Flang preprocessor.

-D<macro>=<value>¶

Define <macro> to <value> (or 1 if <value> omitted)

-P¶

Disable linemarker output in -E mode

-U<macro>¶

Undefine macro <macro>

Include path management ¶

Flags controlling how #includes are resolved to files.

-I<dir>¶

Add directory to include search path. For C++ inputs, if there are multiple -I options, these directories are searched in the order they are given before the standard system directories are searched. If the same directory is in the SYSTEM include search paths, for example if also specified with -isystem, the -I option will be ignored

-isysroot<dir>¶

Set the system root directory (usually /)

Dumping preprocessor state ¶

Flags allowing the state of the preprocessor to be dumped in various ways.

-dM¶

Print macro definitions in -E mode instead of normal output

Diagnostic options ¶

Flags controlling which warnings, errors, and remarks Flang will generate. See Clang’s Diagnostic Reference for a full list of warning and remark flags.

-R<remark>¶

Enable the specified remark

-Rpass-analysis=<arg>¶

Report transformation analysis from optimization passes whose name matches the given POSIX regular expression

-Rpass-missed=<arg>¶

Report missed transformations by optimization passes whose name matches the given POSIX regular expression

-Rpass=<arg>¶

Report transformations performed by optimization passes whose name matches the given POSIX regular expression

-W<warning>¶

Enable the specified warning

Target-independent compilation options ¶

-cpp¶

Enable predefined and command line preprocessor macros

-fPIC, -fno-PIC¶

-fPIE, -fno-PIE¶

-falternative-parameter-statement¶

Enable the old style PARAMETER statement

-fapprox-func, -fno-approx-func¶

Allow certain math function calls to be replaced with an approximately equivalent calculation

-fassociative-math, -fno-associative-math¶

-fbackslash, -fno-backslash¶

Specify that backslash in string introduces an escape character

-fcolor-diagnostics, -fno-color-diagnostics¶

Enable colors in diagnostics

-fconvert=<arg>¶

Set endian conversion of data for unformatted files

-fdefault-double-8¶

Set the default double precision kind to an 8 byte wide type

-fdefault-integer-8¶

Set the default integer and logical kind to an 8 byte wide type

-fdefault-real-8¶

Set the default real kind to an 8 byte wide type

-ffast-math, -fno-fast-math¶

Allow aggressive, lossy floating-point optimizations

-ffixed-form¶

Process source files in fixed form

-ffixed-line-length=<arg>, -ffixed-line-length-<arg>¶

Set column after which characters are ignored in typical fixed-form lines in the source file

-ffp-contract=<arg>¶

Form fused FP ops (e.g. FMAs): fast (fuses across statements disregarding pragmas) | on (only fuses in the same statement unless dictated by pragmas) | off (never fuses) | fast-honor-pragmas (fuses across statements unless dictated by pragmas). Default is ‘fast’ for CUDA, ‘fast-honor-pragmas’ for HIP, and ‘on’ otherwise. <arg> must be ‘fast’, ‘on’, ‘off’ or ‘fast-honor-pragmas’.

-ffree-form¶

Process source files in free form

-fhonor-infinities, -fno-honor-infinities¶

Specify that floating-point optimizations are not allowed that assume arguments and results are not +-inf.

-fhonor-nans, -fno-honor-nans¶

Specify that floating-point optimizations are not allowed that assume arguments and results are not NANs.

-fimplicit-none, -fno-implicit-none¶

No implicit typing allowed unless overridden by IMPLICIT statements

-finput-charset=<arg>¶

Specify the default character set for source files

-fintegrated-as, -fno-integrated-as¶

Enable the integrated assembler

-fintrinsic-modules-path <dir>¶

This option specifies the location of pre-compiled intrinsic modules,: if they are not in the default location expected by the compiler.

-flarge-sizes¶

Use INTEGER(KIND=8) for the result type in size-related intrinsics

-flogical-abbreviations, -fno-logical-abbreviations¶

Enable logical abbreviations

-flto=<arg>, -flto (equivalent to -flto=full), -flto=auto (equivalent to -flto=full), -flto=jobserver (equivalent to -flto=full)¶

Set LTO mode. <arg> must be ‘thin’ or ‘full’.

-fms-runtime-lib=<arg>¶

Specify Visual Studio C runtime library. “static” and “static_dbg” correspond to the cl flags /MT and /MTd which use the multithread, static version. “dll” and “dll_dbg” correspond to the cl flags /MD and /MDd which use the multithread, dll version. <arg> must be ‘static’, ‘static_dbg’, ‘dll’ or ‘dll_dbg’.

-fno-fortran-main¶

Do not include Fortran_main.a (provided by Flang) when linking

-fomit-frame-pointer, -fno-omit-frame-pointer¶

Omit the frame pointer from functions that don’t need it. Some stack unwinding cases, such as profilers and sanitizers, may prefer specifying -fno-omit-frame-pointer. On many targets, -O1 and higher omit the frame pointer by default. -m[no-]omit-leaf-frame-pointer takes precedence for leaf functions

-fopenacc¶

Enable OpenACC

-fopenmp¶

Parse OpenMP pragmas and generate parallel code.

-fopenmp-target-debug, -fno-openmp-target-debug¶

Enable debugging in the OpenMP offloading device RTL

-fopenmp-version=<arg>¶

Set OpenMP version (e.g. 45 for OpenMP 4.5, 51 for OpenMP 5.1). Default value is 11 for Flang

-fopenmp=<arg>¶

-foptimization-record-file=<file>¶

Specify the output name of the file containing the optimization remarks. Implies -fsave-optimization-record. On Darwin platforms, this cannot be used with multiple -arch <arch> options.

-foptimization-record-passes=<regex>¶

Only include passes which match a specified regular expression in the generated optimization record (by default, include all passes)

-fpass-plugin=<dsopath>¶

Load pass plugin from a dynamic shared object file (only with new pass manager).

-fpic, -fno-pic¶

-fpie, -fno-pie¶

-freciprocal-math, -fno-reciprocal-math¶

Allow division operations to be reassociated

-fropi, -fno-ropi¶

Generate read-only position independent code (ARM only)

-frwpi, -fno-rwpi¶

Generate read-write position independent code (ARM only)

-fsave-optimization-record, -fno-save-optimization-record¶

Generate a YAML optimization record file

-fsave-optimization-record=<format>¶

Generate an optimization record file in a specific format

-fsigned-zeros, -fno-signed-zeros¶

-funderscoring, -fno-underscoring¶

Appends one trailing underscore to external names

-fuse-ld=<arg>¶

-fveclib=<arg>¶

Use the given vector functions library. <arg> must be ‘Accelerate’, ‘libmvec’, ‘MASSV’, ‘SVML’, ‘SLEEF’, ‘Darwin_libsystem_m’, ‘ArmPL’, ‘AMDLIBM’ or ‘none’.

-fxor-operator, -fno-xor-operator¶

Enable .XOR. as a synonym of .NEQV.

-nocpp¶

Disable predefined and command line preprocessor macros

-pedantic, --pedantic¶

Warn on language extensions

Common Offloading options ¶

--offload-arch=<arg>, --no-offload-arch=<arg>¶

Specify an offloading device architecture for CUDA, HIP, or OpenMP. (e.g. sm_35). If ‘native’ is used the compiler will detect locally installed architectures. For HIP offloading, the device architecture can be followed by target ID features delimited by a colon (e.g. gfx908:xnack+:sramecc-). May be specified more than once.

--offload-device-only¶

Only compile for the offloading device.

--offload-host-device¶

Compile for both the offloading host and device (default).

--offload-host-only¶

Only compile for the offloading host.

HIP options ¶

--rocm-path=<arg>¶

ROCm installation path, used for finding and automatically linking required bitcode libraries.

Target-dependent compilation options ¶

-march=<arg>¶

For a list of available architectures for the target use ‘-mcpu=help’

-masm=<arg>¶

-mcode-object-version=<arg>¶

Specify code object ABI version. Defaults to 5. (AMDGPU only). <arg> must be ‘none’, ‘4’, ‘5’ or ‘6’.

-mcpu=<arg>¶

For a list of available CPUs for the target use ‘-mcpu=help’

-mdynamic-no-pic<arg>¶

-mrvv-vector-bits=<arg>¶

Defaults to the vector length agnostic value of “scalable”. Accepts power of 2 values between 64 and 65536. Also accepts “zvl” to use the value implied by -march/-mcpu. (RISC-V only)