DECD, DECH, DECW (vector) Decrement vector by 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 uses the result to decrement all destination vector elements. 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. Green False True True It has encodings from 3 classes: Doubleword , Halfword and Word 0 0 0 0 0 1 0 0 1 1 1 1 1 1 0 0 0 1 DECD <Zdn>.D{, <pattern>{, MUL #<imm>}} if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 64; constant integer dn = UInt(Zdn); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1; 0 0 0 0 0 1 0 0 0 1 1 1 1 1 0 0 0 1 DECH <Zdn>.H{, <pattern>{, MUL #<imm>}} if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 16; constant integer dn = UInt(Zdn); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1; 0 0 0 0 0 1 0 0 1 0 1 1 1 1 0 0 0 1 DECW <Zdn>.S{, <pattern>{, MUL #<imm>}} if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 32; constant integer dn = UInt(Zdn); constant bits(5) pat = pattern; constant integer imm = UInt(imm4) + 1; <Zdn> Is the name of the source and destination scalable vector register, encoded in the "Zdn" field. <pattern> Is the optional pattern specifier, defaulting to ALL, pattern <pattern> 00000 POW2 00001 VL1 00010 VL2 00011 VL3 00100 VL4 00101 VL5 00110 VL6 00111 VL7 01000 VL8 01001 VL16 01010 VL32 01011 VL64 01100 VL128 01101 VL256 0111x #uimm5 101x1 #uimm5 10110 #uimm5 1x0x1 #uimm5 1x010 #uimm5 1xx00 #uimm5 11101 MUL4 11110 MUL3 11111 ALL <imm> Is the immediate multiplier, in the range 1 to 16, defaulting to 1, encoded in the "imm4" field. CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer elements = VL DIV esize; constant integer count = DecodePredCount(pat, esize); constant bits(VL) operand1 = Z[dn, VL]; bits(VL) result; for e = 0 to elements-1 Elem[result, e, esize] = Elem[operand1, e, esize] - (count * imm); Z[dn, VL] = result;