vmsr

Move Register to VFP System Register

VMSR<c> <spec_reg>, <Rt>

Writes to a VFP system register.

Pseudocode Operation

if ConditionPassed(cond) then
  if Rt == 15 then
    FPSCR[31:28] ← APSR_nzcv
  else
    FPSCR ← Rt

Example

VMSR nzcv, r3

Encoding

Binary Layout
cond
31:28
1110111
27:21
0
20
reg
19:16
Rt
15:12
1010
11:8
0
7
0
6
0
5
1
4
0
3
0
2
0
1
0
0
 
Format VFP System
Opcode 0x0EE00A10
Extension VFP (System)

Operands

  • spec_reg
    FPSCR
  • Rt
    Transfer general-purpose register (load/store)

Related

More in VFP (System)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding Instruction ISA Bit pattern
0x0EE00A10 VMSR{<c>}{<q>} <spec_reg>, <Rt> A32 cond | 1110111 | 0 | reg | Rt | 1010 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0
0xEEE00A10 VMSR{<c>}{<q>} <spec_reg>, <Rt> T32 11101110111 | 0 | reg | Rt | 1010 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0

Description

Move general-purpose register to SIMD&FP Special register moves the value of a general-purpose register to a floating-point System register. Depending on settings in the CPACR, NSACR, HCPTR, and FPEXC registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support. When these settings permit the execution of Advanced SIMD and floating-point instructions:

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    if reg == '0001' then                 // FPSCR
        CheckVFPEnabled(TRUE);
        FPSCR = R[t];
    elsif PSTATE.EL == EL0 then
        UNDEFINED;                        // Non-FPSCR registers accessible only at PL1 or above
    else
        CheckVFPEnabled(FALSE);           // Non-FPSCR registers are not affected by FPEXC.EN
        case reg of
            when '0000'                   // VMSR access to FPSID is ignored
            when '1000'
                FPEXC = R[t];
            otherwise
                Unreachable();   // Dealt with above or in encoding-specific pseudocode