Encoding:

P32A

001000

rt

rs

ac

10

010

010

111

111

6

5

5

2

2

3

3

3

3

Format: 

DPSU.H.QBL ac, rs, rt

DSP

Dot Product with Subtraction on Vector Unsigned Byte Elements

Purpose:

Dot Product with Subtraction on Vector Unsigned Byte Elements

Element-wise multiplication of two left-most elements from the four elements of each oftwo vectors of unsigned bytes, subtracting the sum of the products from the specified 64-bit accumulator register.

Description: 

ac = ac - zero_extend((rs31..24 * rt31..24) + (rs23..16 * rt23..16))

The two left-most elements of the four unsigned byte elements of each of registers rt and rs are multiplied together using unsigned arithmetic to generate two 16-bit unsigned intermediate products. The intermediate products are then zero-extended to 64 bits and subtracted from the specified 64-bit HI/LO accumulator. The result of the subtraction is written back to the specified 64-bit HI/LO accumulator.

The value of ac can range from 0 to 3; a v alue of 0 refers to the original HI/LO register pair of the MIPS32 architecture.

This instruction does not set any bits in the ouflag field in the DSPControl register.

Restrictions:

No data-dependent exceptions are possible.

The operands must be values in the specified format. If they are not, the result is UNPREDICTABLE and the values of the operand vectors become UNPREDICTABLE.

Operation: 

ValidateAccessToDSPResources()
tempB15..0 = multiplyU8U8( GPR[rs]31..24, GPR[rt]31..24 )
tempA15..0 = multiplyU8U8( GPR[rs]23..16, GPR[rt]23..16 )
dotp63..0 = ( 048 || tempB15..0 ) + ( 048 || tempA15..0 )
tempC63..0 = ( HI[ac]31..0 || LO[ac]31..0 ) - dotp63..0
( HI[ac]31..0 || LO[ac]31..0 ) = tempC63..32 || tempC31..0

Exceptions:

Reserved Instruction, DSP Disabled