hadd, rhadd

Returns (x + y) >> 1, or (x + y + 1) >> 1

gentype hadd ( gentype x,
  gentype y)
gentype rhadd ( gentype x,
  gentype y)

Description

hadd returns (x+y) >> 1. The intermediate sum does not modulo overflow.

rhadd returns (x+y+1) >> 1. The intermediate sum does not modulo overflow.

Notes

Frequently vector operations need n + 1 bits temporarily to calculate a result. The rhadd instruction gives you an extra bit without needing to upsample and downsample. This can be a profound performance win.

Built-in integer functions can be used to take scalar or vector arguments. We use the generic type name gentype to indicate that the function can take char, char{2|4|8|16}, uchar, uchar{2|4|8|16}, short, short{2|4|8|16}, ushort, ushort{2|4|8|16}, int, int{2|4|8|16}, uint, uint{2|4|8|16}, long, long{2|4|8|16}, ulong, or ulong{2|4|8|16} as the type for the arguments. We use the generic type name ugentype to refer to unsigned versions of gentype. For example, if gentype is char4, ugentype is uchar4.

For any specific use of a function, the actual type has to be the same for all arguments and the return type unless otherwise specified.

Specification

OpenCL Specification

Also see

Integer Functions

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