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Conventions and Feedback Introduction Compiler Command-line Options Language Extensions Compiler-specific Features Keywords and operators __align __alignof__ __ALIGNOF__ __asm __forceinline __global_reg __inline __int64 __INTADDR__ __irq __packed __pure __smc __softfp __svc __svc_indirect __svc_indirect_r7 __value_in_regs __weak __writeonly __declspec attributes __declspec(dllexport) __declspec(dllimport) __declspec(noinline) __declspec(noreturn) __declspec(nothrow) __declspec(notshared) __declspec(thread) Function attributes __attribute__((alias)) function attribute __attribute__((always_inline)) function attribute __attribute__((const)) function attribute __attribute__((constructor[(priority)])) function __attribute__((deprecated)) function attribute __attribute__((destructor[(priority)])) function a __attribute__((format_arg(string-index))) function __attribute__((malloc)) function attribute __attribute__((noinline)) function attribute __attribute__((nomerge)) function attribute __attribute__((nonnull)) function attribute __attribute__((noreturn)) function attribute __attribute__((notailcall)) function attribute __attribute__((pcs("calling_convention") __attribute__((pure)) function attribute __attribute__((section("name"))) functio __attribute__((unused)) function attribute __attribute__((used)) function attribute __attribute__((visibility("visibility_type&qu __attribute__((weak)) function attribute __attribute__((weakref("target"))) funct Type attributes __attribute__((bitband)) type attribute __attribute__((aligned)) type attribute __attribute((packed)) type attribute __attribute__((transparent_union)) type attribute Variable attributes __attribute__((alias)) variable attribute __attribute__((at(address))) variable attribute __attribute__((aligned)) variable attribute __attribute__((deprecated)) variable attribute __attribute__((noinline)) constant variable attrib __attribute__((packed)) variable attribute __attribute__((section("name"))) variabl __attribute__((transparent_union)) variable attrib __attribute__((unused)) variable attribute __attribute__((used)) variable attribute __attribute__((visibility("visibility_type&qu __attribute__((weak)) variable attribute __attribute__((weakref("target"))) varia __attribute__((zero_init)) variable attribute Pragmas #pragma anon_unions, #pragma no_anon_unions #pragma arm #pragma arm section [section_type_list] #pragma diag_default tag[,tag,...] #pragma diag_error tag[,tag,...] #pragma diag_remark tag[,tag,...] #pragma diag_suppress tag[,tag,...] #pragma diag_warning tag[, tag, ...] #pragma exceptions_unwind, #pragma no_exceptions_u #pragma hdrstop #pragma import symbol_name #pragma import(__use_full_stdio) #pragma import(__use_smaller_memcpy) #pragma inline, #pragma no_inline #pragma no_pch #pragma Onum #pragma once #pragma Ospace #pragma Otime #pragma pack(n) #pragma pop #pragma push #pragma softfp_linkage, #pragma no_softfp_linkage #pragma thumb #pragma unroll [(n)] #pragma unroll_completely #pragma weak symbol, #pragma weak symbol1 = symbol Instruction intrinsics __breakpoint intrinsic __cdp intrinsic __clrex intrinsic __clz intrinsic __current_pc intrinsic __current_sp intrinsic __disable_fiq intrinsic __disable_irq intrinsic __enable_fiq intrinsic __enable_irq intrinsic __fabs intrinsic __fabsf intrinsic __force_stores intrinsic __ldrex intrinsic __ldrexd intrinsic __ldrt intrinsic __memory_changed intrinsic __nop intrinsic __pld intrinsic __pldw intrinsic __pli intrinsic __promise intrinsic __qadd intrinsic __qdbl intrinsic __qsub intrinsic __rbit intrinsic __rev intrinsic __return_address intrinsic __ror intrinsic __schedule_barrier intrinsic __semihost intrinsic __sev intrinsic __sqrt intrinsic __sqrtf intrinsic __ssat intrinsic __strex intrinsic __strexd intrinsic __strt intrinsic __swp intrinsic __usat intrinsic __wfe intrinsic __wfi intrinsic __yield intrinsic ARMv6 SIMD intrinsics ETSI basic operations C55x intrinsics VFP status intrinsic __vfp_status intrinsic Fused Multiply Add (FMA) intrinsics Named register variables Predefined macros Built-in function name variables C and C++ Implementation Details Semihosting ARMv6 SIMD Instruction Intrinsics Via File Syntax Standard C Implementation Definition Standard C++ Implementation Definition C and C++ Compiler Implementation Limits

Compiler Reference Guide

__swp intrinsic

ARM Compiler toolchain v5.02 for µVision Compiler Reference
Home > Compiler-specific Features > __swp intrinsic

__swp intrinsic

This intrinsic inserts a SWP{size} instruction into the instruction stream generated by the compiler. It enables you to swap data between memory locations from your C or C++ code.

Note

The use of SWP and SWPB is deprecated in ARMv6 and above.

Show/hideSyntax

unsigned int __swp(unsigned int val, volatile void *ptr)

where:

val

Is the data value to be written to memory.

ptr

Points to the address of the data to be written to in memory. To specify the size of the data to be written, cast the parameter to an appropriate integral type.

Table 21. Access widths supported by the __swp intrinsic

InstructionSize of data loadedC cast
SWPBunsigned byte(char *)
SWPword(int *)

Show/hideReturn value

The __swp intrinsic returns the data value that previously, is in the memory address pointed to by ptr, before this value is overwritten by val.

Show/hideExample

int foo(void)
{
    int loc=0xff;
    return(__swp(0x20, (volatile int *)loc));
}

Compiling this code produces

||foo|| PROC
    MOV      r1, #0xff
    MOV      r0, #0x20
    SWP      r0, r0, [r1]
    BX       lr
    ENDP

Show/hideSee also

Copyright © 2007-2008, 2011-2012 ARM. All rights reserved.ARM DUI 0376D
Non-ConfidentialID062912
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Home > Compiler-specific Features > __swp intrinsic

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