RealView® Compilation Tools Assembler Guide 5.4.6. MRS and MSR

5.4.6. MRS and MSR

Transfer contents between an ARM register and a NEON / VFP status register.

Syntax

MRS{cond} Rd, VFPsysreg

MSR{cond} VFPsysreg, Rd

where:

cond

is an optional condition code (see Condition codes).

VFPsysreg

is the VFP system register, usually FPSCR, FPSID, or FPEXC (see VFP registers).

Rd

is the ARM register. Rd must not be r15.

It can be APSR_nzcv, if VFPsysreg is FPSCR. In this case, the floating-point status flags are transferred into the corresponding flags in the ARM CPSR.

Usage

The MRS instruction transfers the contents of VFPsysreg into Rd.

The MSR instruction transfers the contents of Rd into VFPsysreg.

Note

These instructions stall the ARM until all current NEON / VFP operations complete.

Exceptions

These instructions do not produce any exceptions.

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