RealView Compilation Tools Compiler Reference Guide - ARM ...

Compiler-specific Features
See also
• --thumb on page 2-86
• LDR and STR (User mode) on page 4-18 in the Assembler Guide.
4.7.41 __swp
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.
Syntax
unsigned int __swp(unsigned int val, volatile void *ptr)
where:
val
ptr
Is the data value to be written to memory.
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 4-12 Access widths supported by the __swp intrinsic
Instruction Size of data loaded C cast
SWPB unsigned byte (char *)
SWP word (int *)
Return value
The __swp intrinsic returns the data value that previously, is in the memory address
pointed to by ptr, before this value is overwitten by val.
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