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

VMAX (floating-point)

Vector Maximum compares corresponding elements in two vectors, and copies the larger of each pair into the corresponding element in the destination vector.

The operand vector elements are floating-point numbers.

Depending on settings in the CPACR, NSACR, and HCPTR 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 Q == '1' && (Vd<0> == '1' || Vn<0> == '1' || Vm<0> == '1') then UNDEFINED;
if sz == '1' && !HaveFP16Ext() then UNDEFINED;
maximum = (op == '0');
case sz of
    when '0' esize = 32; elements = 2;
    when '1' esize = 16; elements = 4;
d = UInt(D:Vd);  n = UInt(N:Vn);  m = UInt(M:Vm);  regs = if Q == '0' then 1 else 2;

T1

if Q == '1' && (Vd<0> == '1' || Vn<0> == '1' || Vm<0> == '1') then UNDEFINED;
if sz == '1' && !HaveFP16Ext() then UNDEFINED;
if sz == '1' && InITBlock() then UNPREDICTABLE;
maximum = (op == '0');
case sz of
    when '0' esize = 32; elements = 2;
    when '1' esize = 16; elements = 4;
d = UInt(D:Vd);  n = UInt(N:Vn);  m = UInt(M:Vm);  regs = if Q == '0' then 1 else 2;

CONSTRAINED UNPREDICTABLE behavior

If sz == '1' && 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

Floating-point maximum and minimum

• max(+0.0, -0.0) = +0.0
• If any input is a NaN, the corresponding result element is the default NaN.

if ConditionPassed() then
    EncodingSpecificOperations();  CheckAdvSIMDEnabled();
    for r = 0 to regs-1
        for e = 0 to elements-1
            op1 = Elem[D[n+r],e,esize];  op2 = Elem[D[m+r],e,esize];
            if maximum then
                Elem[D[d+r],e,esize] = FPMax(op1, op2, StandardFPSCRValue());
            else
                Elem[D[d+r],e,esize] = FPMin(op1, op2, StandardFPSCRValue());