This intrinsic inserts a WFI instruction into
the instruction stream generated by the compiler.
In some architectures, for example the v6T2 architecture,
the WFI instruction executes as a NOP instruction.
SyntaxThe compiler does not recognize the __wfi intrinsic
when compiling for a target that does not support the WFI instruction.
The compiler generates either a warning or an error in this case.
NOP in the Assembler Reference.
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