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Compiler Reference Guide

Preface Arm Compiler Tools Overview armclang Reference armclang Command-line Options Summary of armclang command-line options -C (armclang) -c (armclang) -D -E -e -fbare-metal-pie -fbracket-depth=N -fcommon, -fno-common -fdata-sections, -fno-data-sections -ffast-math, -fno-fast-math -ffixed-rN -ffp-mode -ffunction-sections, -fno-function-sections -fident, -fno-ident @file -fldm-stm, -fno-ldm-stm -fno-builtin -fno-inline-functions -flto, -fno-lto -fexceptions, -fno-exceptions -fomit-frame-pointer, -fno-omit-frame-pointer -fpic, -fno-pic -fropi, -fno-ropi -fropi-lowering, -fno-ropi-lowering -frwpi, -fno-rwpi -frwpi-lowering, -fno-rwpi-lowering -fsanitize -fshort-enums, -fno-short-enums -fshort-wchar, -fno-short-wchar -fstack-protector, -fstack-protector-all, -fstack- -fstrict-aliasing, -fno-strict-aliasing -fsysv, -fno-sysv -ftrapv -fvectorize, -fno-vectorize -fvisibility -fwrapv -g, -gdwarf-2, -gdwarf-3, -gdwarf-4 (armclang) -I -include -L -l -M, -MM -MD, -MMD -MF -MG -MP -MT -march -marm -masm -mbig-endian -mbranch-protection -mcmodel -mcmse -mcpu -mexecute-only -mfloat-abi -mfpu -mimplicit-it -mlittle-endian -mno-neg-immediates -moutline, -mno-outline -mpixolib -munaligned-access, -mno-unaligned-access -mthumb -nostdlib -nostdlibinc -o (armclang) -O (armclang) -pedantic -pedantic-errors -Rpass -S -save-temps -shared (armclang) -std --target -U -u (armclang) -v (armclang) --version (armclang) --version_number (armclang) --vsn (armclang) -W -Wl -Xlinker -x (armclang) -### Compiler-specific Keywords and Operators Compiler-specific keywords and operators __alignof__ __asm __declspec attributes __declspec(noinline) __declspec(noreturn) __declspec(nothrow) __inline __promise __unaligned Global named register variables Compiler-specific Function, Variable, and Type Att Function attributes __attribute__((always_inline)) function attribute __attribute__((cmse_nonsecure_call)) function attr __attribute__((cmse_nonsecure_entry)) function att __attribute__((const)) function attribute __attribute__((constructor(priority))) function at __attribute__((format_arg(string-index))) function __attribute__((interrupt("type"))) function attrib __attribute__((malloc)) function attribute __attribute__((naked)) function attribute __attribute__((noinline)) function attribute __attribute__((nonnull)) function attribute __attribute__((noreturn)) function attribute __attribute__((nothrow)) function attribute __attribute__((pcs("calling_convention"))) functio __attribute__((pure)) function attribute __attribute__((section("name"))) function attribut __attribute__((unused)) function attribute __attribute__((used)) function attribute __attribute__((value_in_regs)) function attribute __attribute__((visibility("visibility_type"))) fun __attribute__((weak)) function attribute __attribute__((weakref("target"))) function attrib Type attributes __attribute__((aligned)) type attribute __attribute__((packed)) type attribute __attribute__((transparent_union)) type attribute Variable attributes __attribute__((alias)) variable attribute __attribute__((aligned)) variable attribute __attribute__((deprecated)) variable attribute __attribute__((packed)) variable attribute __attribute__((section("name"))) variable attribut __attribute__((unused)) variable attribute __attribute__((used)) variable attribute __attribute__((visibility("visibility_type"))) var __attribute__((weak)) variable attribute __attribute__((weakref("target"))) variable attrib Compiler-specific Intrinsics __breakpoint intrinsic __current_pc intrinsic __current_sp intrinsic __disable_fiq intrinsic __disable_irq intrinsic __enable_fiq intrinsic __enable_irq intrinsic __force_stores intrinsic __memory_changed intrinsic __schedule_barrier intrinsic __semihost intrinsic __vfp_status intrinsic Compiler-specific Pragmas #pragma clang system_header #pragma clang diagnostic #pragma clang section #pragma once #pragma pack(...) #pragma unroll[(n)], #pragma unroll_completely #pragma weak symbol, #pragma weak symbol1 = symbol Other Compiler-specific Features ACLE support Predefined macros Inline functions Half-precision floating-point data types Half-precision floating-point number format Half-precision floating-point intrinsics Library support for _Float16 data type BFloat16 floating-point number format TT instruction intrinsics Non-secure function pointer intrinsics armclang Integrated Assembler Syntax of assembly files for integrated assembler Assembly expressions Alignment directives Data definition directives String definition directives Floating-point data definition directives Section directives Conditional assembly directives Macro directives Symbol binding directives Org directive AArch32 Target selection directives AArch64 Target selection directives Space-filling directives Type directive Integrated assembler support for the CSDB instruct armclang Inline Assembler Inline Assembly File-scope inline assembly Inline assembly statements within a function Assembly string Output and input operands Clobber list volatile Inline assembly constraint strings Constraint modifiers Constraint codes Constraint codes common to AArch32 state and AArch Constraint codes for AArch32 state Constraint codes for AArch64 state Using multiple alternative operand constraints Inline assembly template modifiers Template modifiers common to AArch32 state and AAr Template modifiers for AArch32 state Template modifiers for AArch64 state Forcing inline assembly operands into specific reg Symbol references and branches into and out of inl Duplication of labels in inline assembly statement armlink Reference fromelf Reference armar Reference armasm Legacy Assembler Reference Appendixes

-masm

B1.51 -masm

Enables Arm® Development Studio to select the correct assembler for the input assembly source files.

Default

-masm=gnu

Syntax

-masm=assembler

Parameters

The value of assembler can be one of:

auto

Automatically detect the correct assembler from the syntax of the input assembly source file.

If the assembly source file contains GNU syntax assembly code, then invoke armclang integrated assembler.

If the assembly source file contains legacy armasm syntax assembly code, then invoke the legacy armasm assembler. The most commonly used options are translated from the armclang command-line options to the appropriate armasm command-line options.

Note:

In rare circumstances, the auto-detection might select the wrong assembler for the input file. For example, if the input file is a .S file that requires preprocessing, auto-detection might select the wrong assembler. For the files where auto-detection selects the wrong assembler, you must select -masm=gnu or -masm=armasm explicitly.
gnu
Invoke the armclang integrated assembler.
armasm
Invoke the legacy armasm assembler. The most commonly used options are translated from the armclang command-line options to the appropriate armasm command-line options.

Operation

If you use Arm Development Studio to build projects with the CMSIS-Pack, use -masm=auto, because some of the assembly files in the CMSIS-Pack contain legacy armasm syntax assembly code. When invoking the legacy armasm assembler, the most commonly used options are translated from the armclang command-line options to the appropriate armasm command-line options, which the Translatable options table shows.

Table B1-4 Translatable options

armclang option armasm option
-mcpu, -march --cpu
-marm --arm
-mthumb --thumb
-fropi --apcs=/ropi
-frwpi --apcs=/rwpi

-mfloat-abi=soft

-mfloat-abi=softfp

-mfloat-abi=hard

--apcs=/softfp

--apcs=/softfp

--apcs=/hardfp

-mfpu --fpu
-mbig-endian --bigend
-mlittle-endian --littleend
-g -g
-ffp-mode --fpmode
-DNAME --predefine "NAME SETA 1"
-Idir -idir

If you need to provide additional options to the legacy armasm assembler, which are not listed in the Translatable options table, then use -Wa,armasm,option,value. For example:

  • If you want to use the legacy armasm assembler option --show_cmdline to see the command-line options that have been passed to the legacy armasm assembler, then use:

    -Wa,armasm,--show_cmdline
  • If the legacy armasm syntax source file requires the option --predefine "NAME SETA 100", then use:

    -Wa,armasm,--predefine,"NAME SETA 100"
  • If the legacy armasm syntax source file requires the option --predefine "NAME SETS \"Version 1.0\"", then use:

    -Wa,armasm,--predefine,"NAME SETS \"Version 1.0\""

    Note:

    The command-line interface of your system might require you to enter special character combinations to achieve correct quoting, such as \" instead of ".

Note:

Arm Compiler 6 provides the -masm option as a short term solution to enable the assembly of legacy armasm syntax assembly source files. The -masm option will be removed in a future release of Arm Compiler 6. Arm recommends that you migrate all legacy armasm syntax assembly source files into GNU syntax assembly source files. For more information, see Migrating from armasm to the armclang integrated assembler in the Migration and Compatibility Guide.

If you are using the compiler from outside Arm Development Studio, such as from the command-line, then Arm recommends that you do not specify the -masm option, and instead invoke the correct assembler explicitly.

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