CNTB, CNTD, CNTH, CNTW

Set scalar to multiple of predicate constraint element count

Determines the number of active elements implied by the named predicate constraint, multiplies that by an immediate in the range 1 to 16 inclusive, and then places the result in the scalar destination.

The named predicate constraint limits the number of active elements in a single predicate to:

• A fixed number (VL1 to VL256)
• The largest power of two (POW2)
• The largest multiple of three or four (MUL3 or MUL4)
• All available, implicitly a multiple of two (ALL).

Unspecified or out of range constraint encodings generate an empty predicate or zero element count rather than Undefined Instruction exception.

It has encodings from 4 classes: Byte , Doubleword , Halfword and Word

Byte

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 8; constant integer d = UInt(Rd); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1;

Doubleword

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 64; constant integer d = UInt(Rd); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1;

Halfword

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 16; constant integer d = UInt(Rd); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1;

Word

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 32; constant integer d = UInt(Rd); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1;