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Technical Support
On-Line Manuals
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 (armclang)
-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 (armclang)
-save-temps
-shared (armclang)
-std
--target
-U
-u (armclang)
-v (armclang)
--version (armclang)
--version_number (armclang)
--vsn (armclang)
-W (armclang)
-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__((nomerge)) function attribute
__attribute__((nonnull)) function attribute
__attribute__((noreturn)) function attribute
__attribute__((not_tail_called)) function attribut
__attribute__((nothrow)) function attribute
__attribute__((pcs("calling_convention"))) functio
__attribute__((pure)) function attribute
__attribute__((section("name"))) function attribut
__attribute__((target("options"))) function attrib
__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
Volatile variables
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
Supported architecture feature combinations for sp
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
-munaligned-access, -mno-unaligned-access
| Non-Confidential |  PDF version | 101754_0616_01_en | ||
| ||||
| Home > armclang Reference > armclang Command-line Options > -munaligned-access, -mno-unaligned-access | ||||
B1.65 -munaligned-access, -mno-unaligned-access
Enables or disables unaligned accesses to data on Arm® processors.
The compiler defines the __ARM_FEATURE_UNALIGNED macro when -munaligned-access is enabled.
The libraries include special versions of certain library functions designed to
exploit unaligned accesses. When unaligned access support is enabled, using -munaligned-access, the
compilation tools use these library functions to take advantage of unaligned
accesses. When unaligned access support is disabled, using -mno-unaligned-access, these special versions are not used.
Default
-munaligned-access is the default for architectures that support unaligned accesses to data. This default applies to all architectures supported by Arm Compiler 6, except Armv6‑M, and Armv8‑M without the Main Extension.
Usage
-munaligned-access-
Use this option on processors that support unaligned accesses to data, to speed up accesses to packed structures.
Note:
Compiling with this option generates an error for the following architectures:
- Armv6‑M.
- Armv8‑M without the Main Extension.
-mno-unaligned-access-
If unaligned access is disabled, any unaligned data that is wider than 8 bits is accessed 1 byte at a time. For example, fields wider than 8 bits, in packed data structures, are always accessed 1 byte at a time even if they are aligned.
| Non-Confidential | PDF version | 101754_0616_01_en |
| Copyright © 2019–2021 Arm Limited or its affiliates. All rights reserved. |
| Home > armclang Reference > armclang Command-line Options > -munaligned-access, -mno-unaligned-access |
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