# Conditional Select Operators

For conditional select operands, the third and fourth operands determine the type returned. Third and fourth operands with same size, but different signedness, return the nearest common ancestor data type.

Conditional Select Syntax Usage

Return the nearest common ancestor data type if third and fourth operands are of the same size, but different signs.

`I16vec4 R = select_neq(Is16vec4, Is16vec4, Is16vec4, Iu16vec4);`

Conditional Select for Equality

`R0 := (A0 == B0) ? C0 : D0;`

`R1 := (A1 == B1) ? C1 : D1;`

`R2 := (A2 == B2) ? C2 : D2;`

`R3 := (A3 == B3) ? C3 : D3;`

Conditional Select for Inequality

`R0 := (A0 != B0) ? C0 : D0;`

`R1 := (A1 != B1) ? C1 : D1;`

`R2 := (A2 != B2) ? C2 : D2;`

`R3 := (A3 != B3) ? C3 : D3;`

Conditional Select Symbols and Corresponding Intrinsics

Conditional Select For: | Operators | Syntax | Corresponding Intrinsic | Additional Intrinsic (Applies to All)
--- | --- | --- | --- | ---
Equality | select_eq | `R = select_eq(A, B, C, D)` | _mm_cmpeq_pi32 _mm_cmpeq_pi16 _mm_cmpeq_pi8 | _mm_and_si64 _mm_or_si64 _mm_andnot_si64
Inequality | select_neq | `R = select_neq(A, B, C, D)` | _mm_cmpeq_pi32 _mm_cmpeq_pi16 _mm_cmpeq_pi8
Greater Than | select_gt | `R = select_gt(A, B, C, D)` | _mm_cmpgt_pi32 _mm_cmpgt_pi16 _mm_cmpgt_pi8
Greater Than or Equal To | select_ge | `R = select_gt(A, B, C, D)` | _mm_cmpge_pi32 _mm_cmpge_pi16 _mm_cmpge_pi8
Less Than | select_lt | `R = select_lt(A, B, C, D)` | _mm_cmplt_pi32 _mm_cmplt_pi16 _mm_cmplt_pi8
Less Than or Equal To | select_le | `R = select_le(A, B, C, D)` | _mm_cmple_pi32 _mm_cmple_pi16 _mm_cmple_pi8

All conditional select operands must be of the same size. The return data type is the nearest common ancestor of operands `C` and `D`. For conditional select operations using greater-than or less-than operations, the first and second operands must be signed as listed in the table that follows.

Conditional Select Operator Overloading

R | Comparison | A and B | C | D
--- | --- | --- | --- | ---
I32vec2 R | select_eq select_ne | I[s|u]32vec2 | I[s|u]32vec2 | I[s|u]32vec2
I16vec4 R |  | I[s|u]16vec4 | I[s|u]16vec4
I8vec8 R |  | I[s|u]8vec8 | I[s|u]8vec8
I32vec2 R | select_gt select_ge select_lt select_le | Is32vec2 | Is32vec2 | Is32vec2
I16vec4 R |  | Is16vec4 | Is16vec4
I8vec8 R |  | Is8vec8 | Is8vec8

The following table shows the mapping of return values from `R0` to `R7` for any number of elements. The same return value mappings also apply when there are fewer than four return values.

Conditional Select Operator Return Value Mapping

Return Value | A Operands | Available Operators | B Operands | C and D Operands
--- | --- | --- | --- | ---
R0:= | A0 | == | != | > | >= | < | <= | B0 | C0 : D0;
R1:= | A0 | == | != | > | >= | < | <= | B0 | C1 : D1;
R2:= | A0 | == | != | > | >= | < | <= | B0 | C2 : D2;
R3:= | A0 | == | != | > | >= | < | <= | B0 | C3 : D3;
R4:= | A0 | == | != | > | >= | < | <= | B0 | C4 : D4;
R5:= | A0 | == | != | > | >= | < | <= | B0 | C5 : D5;
R6:= | A0 | == | != | > | >= | < | <= | B0 | C6 : D6;
R7:= | A0 | == | != | > | >= | < | <= | B0 | C7 : D7;

Parent topic: Integer Vector Classes