Arm® A32/T32 Instruction Set Architecture: Armv8, for Armv8-A architecture profile Documentation

VNMUL

Vector Negate Multiply multiplies together two floating-point register values, and writes the negation of the result to the destination 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.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

if FPSCR.Len != '000' || FPSCR.Stride != '00' then UNDEFINED;
if size == '01' && !HaveFP16Ext() then UNDEFINED;
if size == '01' && cond != '1110' then UNPREDICTABLE;
vtype = VFPNegMul_VNMUL;
case size of
    when '01' esize = 16; d = UInt(Vd:D); n = UInt(Vn:N); m = UInt(Vm:M);
    when '10' esize = 32; d = UInt(Vd:D); n = UInt(Vn:N); m = UInt(Vm:M);
    when '11' esize = 64; d = UInt(D:Vd); n = UInt(N:Vn); m = UInt(M:Vm);

CONSTRAINED UNPREDICTABLE behavior

If size == '01' && cond != '1110', then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as if it passes the Condition code check.
• The instruction executes as NOP. This means it behaves as if it fails the Condition code check.

T1

if FPSCR.Len != '000' || FPSCR.Stride != '00' then UNDEFINED;
if size == '01' && !HaveFP16Ext() then UNDEFINED;
if size == '01' && InITBlock()  then UNPREDICTABLE;
vtype = VFPNegMul_VNMUL;
case size of
    when '01' esize = 16; d = UInt(Vd:D); n = UInt(Vn:N); m = UInt(Vm:M);
    when '10' esize = 32; d = UInt(Vd:D); n = UInt(Vn:N); m = UInt(Vm:M);
    when '11' esize = 64; d = UInt(D:Vd); n = UInt(N:Vn); m = UInt(M:Vm);

CONSTRAINED UNPREDICTABLE behavior

If size == '01' && InITBlock(), then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as if it passes the Condition code check.
• The instruction executes as NOP. This means it behaves as if it fails the Condition code check.

Assembler Symbols

enumeration VFPNegMul {VFPNegMul_VNMLA, VFPNegMul_VNMLS, VFPNegMul_VNMUL};

if ConditionPassed() then
    EncodingSpecificOperations();  CheckVFPEnabled(TRUE);
    case esize of
        when 16
            product16 = FPMul(S[n]<15:0>, S[m]<15:0>, FPSCR[]);
            case vtype of
                when VFPNegMul_VNMLA  S[d] = Zeros(16) : FPAdd(FPNeg(S[d]<15:0>), FPNeg(product16), FPSCR[]);
                when VFPNegMul_VNMLS  S[d] = Zeros(16) : FPAdd(FPNeg(S[d]<15:0>), product16, FPSCR[]);
                when VFPNegMul_VNMUL  S[d] = Zeros(16) : FPNeg(product16);
        when 32
            product32 = FPMul(S[n], S[m], FPSCR[]);
            case vtype of
                when VFPNegMul_VNMLA  S[d] = FPAdd(FPNeg(S[d]), FPNeg(product32), FPSCR[]);
                when VFPNegMul_VNMLS  S[d] = FPAdd(FPNeg(S[d]), product32, FPSCR[]);
                when VFPNegMul_VNMUL  S[d] = FPNeg(product32);
        when 64
            product64 = FPMul(D[n], D[m], FPSCR[]);
            case vtype of
                when VFPNegMul_VNMLA  D[d] = FPAdd(FPNeg(D[d]), FPNeg(product64), FPSCR[]);
                when VFPNegMul_VNMLS  D[d] = FPAdd(FPNeg(D[d]), product64, FPSCR[]);
                when VFPNegMul_VNMUL  D[d] = FPNeg(product64);