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|Home > Using the Inline and Embedded Assemblers of the ARM Compiler > Inline assembler register list operands in C and C++ code|
A register list can contain a maximum of 16 operands. These operands can be virtual registers or expression register operands.
The order that virtual registers and expression operands are specified in a register list
is significant. The register list operands are read or written in left-to-right order. The
first operand uses the lowest address, and subsequent operands use addresses formed by
incrementing the previous address by four. This behavior is in contrast to the usual
operation of the
STM instructions where the lowest
numbered physical register is always stored to the lowest memory address. This difference in
behavior is a consequence of the virtualization of registers.
An expression operand or virtual register can appear more than once in a register list and is used each time it is specified.
The base register is updated, if specified. The update overwrites any value loaded into the base register during a memory load operation.
The inline assembler does not support operating on User mode registers when in a privileged
mode, by specifying
^ after a register list.