Migration of compiler command-line options from Arm Compiler 5 to Arm Compiler 6

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Arm^® Compiler Migration and Compatibility Guide

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Home > Migrating from armcc to armclang > Migration of compiler command-line options from Arm Compiler 5 to Arm Compiler 6

3.1 Migration of compiler command-line options from Arm^® Compiler 5 to Arm^® Compiler 6

Arm^® Compiler 6 provides many command-line options, including most Clang command-line options and several Arm-specific options.

Note:

This topic includes descriptions of [COMMUNITY] features. See Support level definitions.

The following table describes the most common Arm Compiler 5 command-line options, and shows the equivalent options for Arm Compiler 6.

More information about command-line options is available:

The Arm^® Compiler Reference Guide provides more information about the supported command-line options. The options described are fully supported, unless the level of support is indicated.
For a full list of Clang command-line options, see the Clang and LLVM documentation.

Table 3-1 Comparison of compiler command-line options in Arm Compiler 5 and Arm Compiler 6

Arm Compiler 5 option	Arm Compiler 6 option	Description
`--allow_fpreg_for_nonfpdata`, `--no_allow_fpreg_for_nonfpdata`	`-mimplicit-float`, `-mno-implicit-float` [COMMUNITY]	Enables or disables the use of VFP and SIMD registers and data transfer instructions for non-VFP and non-SIMD data.
`--apcs=/nointerwork`	No equivalent.	Disables interworking between A32 and T32 code. Interworking is always enabled in Arm Compiler 6.
`--apcs=/ropi` `--apcs=/noropi`	`-fropi` `-fno-ropi`	Enables or disables the generation of Read-Only Position Independent (ROPI) code.
`--apcs=/rwpi` `--apcs=/norwpi`	`-frwpi` `-fno-rwpi`	Enables or disables the generation of Read Write Position Independent (RWPI) code.
`--arm`	`-marm`	Targets the A32 instruction set. The compiler is permitted to generate both A32 and T32 code, but recognizes that A32 code is preferred.
`--arm_only`	`No equivalent.`	Enforces A32 instructions only. The compiler does not generate T32 instructions.
`--asm`	`-save-temps`	Instructs the compiler to generate intermediate assembly files as well as object files.
`--bigend`	`-mbig-endian`	Generates code for big-endian data.
`-c`	`-c`	Performs the compilation step, but not the link step.
`--c90`	`-xc -std=c90`	Enables the compilation of C90 source code. `-xc` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension.
`--c90 --gnu`	`-xc -std=gnu90`	Enables the compilation of C90 source code with additional GNU extensions. `-xc` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension.
`--c99`	`-xc -std=c99`	Enables the compilation of C99 source code. `-xc` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension.
`--c99 --gnu`	`-xc -std=gnu99`	Enables the compilation of C99 source code with additional GNU extensions. `-xc` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension.
`--cpp`	`-xc++ -std=c++03`	Enables the compilation of C++03 source code. `-xc++` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension. The default C++ language standard is different between Arm Compiler 5 and Arm Compiler 6.
`--cpp --gnu`	`-xc++ -std=gnu++03`	Enables the compilation of C++03 source code with additional GNU extensions. `-xc++` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension. The default C++ language standard is different between Arm Compiler 5 and Arm Compiler 6.
`--cpp11`	`-xc++ -std=c++11`	Enables the compilation of C++11 source code. `-xc++` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension. The default C++ language standard is different between Arm Compiler 5 and Arm Compiler 6.
`--cpp11 --gnu`	`-xc++ -std=gnu++11`	Enables the compilation of C++11 source code with additional GNU extensions. `-xc++` is a positional argument and only affects subsequent input files on the command-line. It is also only required if the input files do not have the appropriate file extension. The default C++ language standard is different between Arm Compiler 5 and Arm Compiler 6.
`--cpp_compat`	No equivalent.	Compiles C++ code to maximize binary compatibility.
`--cpu=8-A.32`	`--target=arm-arm-none-eabi -march=armv8-a`	Targets Armv8‑A and AArch32 state.
`--cpu 8-A.64`	`--target=aarch64-arm-none-eabi`	Targets Armv8‑A and AArch64 state. (Implies `-march=armv8-a` if `-mcpu` is not specified.)
`--cpu=7-A`	`--target=arm-arm-none-eabi -march=armv7-a`	Targets the Armv7‑A architecture.
`--cpu=Cortex-M4`	`--target=arm-arm-none-eabi -mcpu=cortex-m4`	Targets the Cortex^®-M4 processor.
`--cpu=Cortex-A15`	`--target=arm-arm-none-eabi -mcpu=cortex-a15`	Targets the Cortex‑A15 processor.
`-D`	`-D`	Defines a preprocessing macro.
`--depend`	`-MF`	Specifies a filename for the makefile dependency rules.
`--depend_dir`	No equivalent. Use `-MF` to specify each dependency file individually.	Specifies the directory for dependency output files.
`--depend_format=unix_escaped`		Dependency file entries use UNIX-style path separators and escapes spaces with `\`. This is the default in Arm Compiler 6.
`--depend_system_headers`, `--no_depend_system_headers`	No direct equivalent to the standalone command-line option. However, see the Arm Compiler 5 entries in this table for `--md`, `--md --no_depend_system_headers`, and `--mm`.	Enables and disables the output of system include dependency lines when generating makefile dependency information using either the `-M` option or the `--md` option.
`--depend_target`	`-MT`	Changes the target name for the makefile dependency rule.
`--diag_error`	`-Werror`	Turn compiler warnings into errors.
`--diag_suppress=foo`	`-Wno-foo`	Suppress warning message `foo`. The error or warning codes might be different between Arm Compiler 5 and Arm Compiler 6.
`-E`	`-E`	Executes only the preprocessor step.
`--enum_is_int`	`-fno-short-enums`, `-fshort-enums`	Sets the minimum size of an enumeration type. By default Arm Compiler 5 does not set a minimum size. By default Arm Compiler 6 uses `-fno-short-enums` to set the minimum size to 32-bit.
`--forceline`	No equivalent.	Forces aggressive inlining of functions. Arm Compiler 6 automatically decides whether to inline functions depending on the optimization level.
`--fpmode=std`	`-ffp-mode=std`	Provides IEEE-compliant code with no IEEE exceptions, NaNs, and Infinities. Denormals are sign preserving. This is the default.
`--fpmode=fast`	`-ffp-mode=fast`	Similar to the default behavior, but also performs aggressive floating-point optimizations and therefore it is not IEEE-compliant.
`--fpmode=ieee_full`	`-ffp-mode=full`	Provides full IEEE support, including exceptions.
`--fpmode=ieee_fixed` `--fpmode=ieee_no_fenv`	There are no supported equivalent options.	There might be community features that provide these IEEE floating-point modes.
`--fpu` For example, `--fpu=fpv5_d16`	`-mfpu` For example, `-mfpu=fpv5-d16`	Specifies the target FPU architecture. Note: `--fpu=none` checks the source code for floating-point operations, and if any are found it produces an error. `-mfpu=none` prevents the compiler from using hardware-based floating-point functions. If the compiler encounters floating-point types in the source code, it uses software-based floating-point library functions. The option values might be different. For example `fpv5_d16` in Arm Compiler 5 is equivalent to `fpv5-d16` in Arm Compiler 6, and targets the FPv5-D16 floating-point extension.
`-I`	`-I`	Adds the specified directories to the list of places that are searched to find included files.
`--global_reg=reg_name`	`-ffixed-rN`	Prevents the compiler from using the specified core register, unless the use is required for Arm ABI compliance. In Arm Compiler 5, `reg_name` is an integer starting from `1` to `8`, which maps to registers R4 to R11. In Arm Compiler 6, `N` is an integer starting from `5` to `11`, which maps to registers R5 to R11.
`--ignore_missing_headers`	`-MG`	Prints dependency lines for header files even if the header files are missing.
`--inline`	Default at `-O2` and `-O3`.	There is no equivalent of the `--inline` option. Arm Compiler 6 automatically decides whether to inline functions at optimization levels `-O2` and `-O3`.
`-J`	`-isystem`	Adds the specified directories to the list of places that are searched to find included system header files.
`-L`	`-Xlinker`	Specifies command-line options to pass to the linker when a link step is being performed after compilation.
`--library_interface=armcc`	This is the default.	Arm Compiler 6 by default uses the Arm standard C library.
`--library_interface=lib` Where `lib` is one of: `aeabi_clib` `aeabi_clib90` `aeabi_clib99`	`-nostdlib -nostdlibinc -fno-builtin`	Specifies that the compiler output works with any ISO C library compliant with the Arm Embedded Application Binary Interface (AEABI).
`--library_interface=lib` Where `lib` is not one of: `aeabi_clib` `aeabi_clib90` `aeabi_clib99` `armcc`	No equivalent.	Arm Compiler 6 assumes the use of an AEABI compliant library.
`--licretry`	No equivalent.	There is no equivalent of the `--licretry` option. The Arm Compiler 6 tools automatically retry failed attempts to obtain a license.
`--list_macros`	`-E -dM`	List all the macros that are defined at the end of the translation unit, including the predefined macros.
`--littleend`	`-mlittle-endian`	Generates code for little-endian data.
`--lower_ropi`, `--no_lower_ropi`	`-fropi-lowering`, `-fno-ropi-lowering`	Enables or disables less restrictive C when generating Read-Only Position Independent (ROPI) code. Note: In Arm Compiler 5, when`--acps=/ropi` is specified, `--lower_ropi` is not switched on by default. In Arm Compiler 6, when `-fropi` is specified, `-fropi-lowering` is switched on by default.
`--lower_rwpi`, `--no_lower_rwpi`	`-frwpi-lowering`, `-fno-rwpi-lowering`	Enables or disables less restrictive C when generating Read Write Position Independent (RWPI) code.
`-M`	`-M`	Instructs the compiler to produce a list of makefile dependency lines suitable for use by a make utility.
`--md`	`-MD`	Creates makefile dependency files, including the system header files. In Arm Compiler 5, this is equivalent to `--md --depend_system_headers`.
`--md --no_depend_system_headers`	`-MMD`	Creates makefile dependency files, without the system header files.
`--mm`	`-MM`	Creates a single makefile dependency file, without the system header files. In Arm Compiler 5, this is equivalent to `-M --no_depend_system_headers`.
`--multifile`, `--no_multifile`	No direct equivalent. However, see Optimizing across modules with Link-Time Optimization in the Arm^® Compiler User Guide.	Enables and disables optimizations between multiple source files.
`--no_comment_section`	`-fno-ident`	Removes the `.comment` section from object files.
`--no_exceptions`	`-fno-exceptions`	Disables the generation of code needed to support C++ exceptions. Note: For C++ code, Arm Compiler 6 defaults to `-fexceptions`. As a result, there might be a large increase in the code size. If you use `-fno_exceptions`, then the code size is in the range of that created with Arm Compiler 5.
`--no_hide_all`	`-fvisibility=default`	Sets the default visibility of ELF symbols to the specified option, unless overridden in the source with the `__attribute__((visibility("visibility_type")))` attribute. The default is `-fvisibility=hidden`. Note: The behavior of armclang `-fvisibility=hidden` is different from that of the armcc `--hide-all` option. With armclang `-fvisibility=hidden`, `extern` declarations are visible, and all other symbols are hidden. With armcc `--hide-all`, all symbols are hidden.
`--no_protect_stack`	`-fno-stack-protector`	Explicitly disables stack protection. See 3.2 Arm^® Compiler 5 and Arm^® Compiler 6 stack protection behavior for more information.
`-no_rtti`, `-no_rtti_data`	`-fno-rtti` [ALPHA]	C++ only. `-fno-rtti` [ALPHA] disables the generation of code that is needed to support Run Time Type Information (RTTI) features.
`-o`	`-o`	Specifies the name of the output file.
`-Onum`	`-Onum`	Specifies the level of optimization to be used when compiling source files. The default for Arm Compiler 5 is `-O2`. The default for Arm Compiler 6 is `-O0`. For Arm Compiler 6, Arm recommends `-O1` rather than `-O0` for best trade-off between debug view, code size, and performance. For more information, see Optimization differences.
`-Ospace`	`-Oz / -Os`	Performs optimizations to reduce image size at the expense of a possible increase in execution time.
`-Otime`	This is the default.	Performs optimizations to reduce execution time at the expense of a possible increase in image size. There is no equivalent of the `-Otime` option. Arm Compiler 6 optimizes for execution time by default, unless you specify the `-Os` or `-Oz` options.
`--phony_targets`	`-MP`	Emits dummy makefile rules.
`--preinclude`	`-include`	Include the source code of a specified file at the beginning of the compilation.
`--protect_stack`	`-fstack-protector`,`-fstack-protector-strong`	Enables stack protection on vulnerable functions. See 3.2 Arm^® Compiler 5 and Arm^® Compiler 6 stack protection behavior for more information.
`--protect_stack_all`	`-fstack-protector-all`	Enables stack protection on all functions. See 3.2 Arm^® Compiler 5 and Arm^® Compiler 6 stack protection behavior for more information.
`--relaxed_ref_def`	`-fcommon`	Places zero-initialized definitions in a common block.
`--retain`	`-O`	The optimization level to use for the best code coverage might depend on your source code. In Arm Compiler 5 the `--retain` option disables specific optimizations by name. There is no direct equivalent of this for Arm Compiler 6. Instead you will need to select the optimization level which best suits your needs. See -O in the Arm^® Compiler Reference Guide for more information.
`-S`	`-S`	Outputs the disassembly of the machine code that the compiler generates. The output from this option differs between releases. Arm Compiler 5 produces output with `armasm` syntax while Arm Compiler 6 produces output with GNU syntax.
`--show_cmdline`	`-v`	Shows how the compiler processes the command-line. The commands are shown normalized, and the contents of any via files are expanded.
`--split_ldm`	`-fno-ldm-stm`	Disables the generation of `LDM` and `STM` instructions. Note that while the `armcc --split_ldm` option limits the size of generated LDM/STM instructions, the `armclang -fno-ldm-stm` option disables the generation of `LDM` and `STM` instructions altogether.
`--split_sections`	`-ffunction-sections`	Generates one ELF section for each function in the source file. In Arm Compiler 6, `-ffunction-sections` is the default. Therefore, the merging of identical constants cannot be done by armclang. Instead, the merging is done by armlink. See Merging identical constants in the Arm^® Compiler Reference Guide for more information.
`--strict`	`-pedantic-errors`	Generate errors if code violates strict ISO C and ISO C++.
`--strict_warnings`	`-pedantic`	Generate warnings if code violates strict ISO C and ISO C++.
`--thumb`	`-mthumb`	Targets the T32 instruction set.
`--no_unaligned_access`, `--unaligned_access`	`-mno-unaligned-access`, `-munaligned-access`	Enables or disables unaligned accesses to data on Arm processors.
`--use_frame_pointer`, `--no_use_frame_pointer`	`-fno-omit-frame-pointer`, `-fomit-frame-pointer`	Controls whether a register is reserved for storing the stack frame pointer.
`--vectorize` `--no_vectorize`	`-fvectorize` `-fno-vectorize`	Enables or disables the generation of Advanced SIMD vector instructions directly from C or C++ code.
`--via`	`@file`	Reads an additional list of compiler options from a file.
`--vla`	No equivalent.	Support for variable length arrays. Arm Compiler 6 automatically supports variable length arrays in accordance with the language standard.
`--vsn`	`--version`	Displays version information and license details. In Arm Compiler 6 you can also use `--vsn`.
`--wchar16`, `--wchar32`	`-fshort-wchar`, `-fno-short-wchar`	Sets the size of `wchar_t` type. The default for Arm Compiler 5 is `--wchar16`. The default for Arm Compiler 6 is `-fno-short-wchar`.

Related information

armclang Command-line Options

Compiler-specific Function, Variable, and Type Attributes

The LLVM Compiler Infrastructure Project

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Migration of compiler command-line options from Arm Compiler 5 to Arm Compiler 6

3.1 Migration of compiler command-line options from Arm^® Compiler 5 to Arm^® Compiler 6

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3.1 Migration of compiler command-line options from Arm® Compiler 5 to Arm® Compiler 6

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3.1 Migration of compiler command-line options from Arm^® Compiler 5 to Arm^® Compiler 6