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Preface 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)) __attribute__((always_inline)) __attribute__((const)) __attribute__((deprecated)) __attribute__((malloc)) __attribute__((noinline)) __attribute__((noreturn)) __attribute__((pure)) __attribute__((section)) __attribute__((unused)) __attribute__((used)) __attribute__((weak)) Type attributes __attribute__((aligned)) __attribute((packed)) __attribute__((transparent_union)) Variable attributes __attribute__((alias)) __attribute__((at(address))) __attribute__((aligned)) __attribute__((deprecated)) __attribute__((packed)) __attribute__((section)) __attribute__((transparent_union)) __attribute__((unused)) __attribute__((used)) __attribute__((weak)) __attribute__((zero_init)) Pragmas #pragma [no_]anon_unions #pragma arm #pragma arm section [section_sort_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 [no_]exceptions_unwind #pragma hdrstop #pragma import symbol_name #pragma [no_]inline #pragma no_pch #pragma Onum #pragma once #pragma Ospace #pragma Otime #pragma pop #pragma push #pragma [no_]softfp_linkage #pragma unroll [(n)] #pragma unroll_completely #pragma thumb Instruction intrinsics __breakpoint __builtin_clz __builtin_constant_p __builtin_expect __builtin_frame_address __builtin_return_address __builtin_popcount __cdp __clrex __clz __current_pc __current_sp __disable_fiq __disable_irq __enable_fiq __enable_irq __fabs __fabsf __force_stores __ldrex __ldrt __memory_changed __nop __pld __pli __qadd __qdbl __qsub __rbit __rev __return_address __ror __schedule_barrier __semihost __sev __sqrt __sqrtf __ssat __strex __strt __swp __usat __wfe __wfi __yield ARMv6 SIMD intrinsics ETSI basic operations C55x intrinsics Named register variables Compiler predefines Predefined macros Function names C and C++ Implementation Details Via File Syntax Standard C Implementation Definition Standard C++ Implementation Definition C and C++ Compiler Implementation Limits__ldrex
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Home > Compiler-specific Features > Instruction intrinsics > __ldrex | |||
This intrinsic inserts an instruction of the form LDREX{size} into the instruction stream generated by the compiler. It enables you to load data from memory in your C or C++ code using an LDREX instruction.
unsigned int __ldrex(volatile void *ptr)
Where:
ptrPoints to the address of the data to be loaded from memory. To specify the size of the data to be loaded, cast the parameter to an appropriate integral type.
The __ldrex intrinsic returns the data loaded from the memory address pointed to by ptr
The compiler does not recognize the __ldrex intrinsic when compiling for a target that does not support the LDREX instruction. The compiler generates either a warning or an error in this case.
The __ldrex intrinsic does not support access to doubleword data. The compiler generates an error if you specify an access width that is not supported.
int foo(void)
{
int loc = 0xff;
return __ldrex((volatile char *)loc);
}
Compiling this code with the command‑line option --device=DLM produces
||foo|| PROC MOVS r0,#0xff LDREXB r0,[r0] BX lr ENDP
LDREX and STREX in the Assembler Guide.
| Copyright © 2007 ARM Limited. All rights reserved. | ARM DUI 0376A |
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