SQDMLALT (indexed)

Signed saturating doubling multiply-add by indexed element (top)

This instruction multiplies the odd-numbered signed elements within each 128-bit segment of the first source vector by the specified signed element in the corresponding second source vector segment, and then doubles the result. Each intermediate value is saturated to the double-width N-bit value's signed integer range -2^(N-1) to (2^(N-1))-1 and is then destructively added to the overlapping double-width elements of the addend and destination vector. Each destination element is saturated to the double-width N-bit element's signed integer range -2^(N-1) to (2^(N-1))-1.

The elements within the second source vector are specified using an immediate index that selects the same element position within each 128-bit vector segment. The index range is from 0 to one less than the number of elements per 128-bit segment.

It has encodings from 2 classes: 32-bit and 64-bit

32-bit
(FEAT_SVE2 || FEAT_SME)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 16; let index : integer = UInt(i3h::i3l); let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(Zda); let sel : integer = 1;

64-bit
(FEAT_SVE2 || FEAT_SME)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 32; let index : integer = UInt(i2h::i2l); let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(Zda); let sel : integer = 1;