Encoding:

Format:

PRECR.QB.PH rd, rs, rt

Purpose:

Precision Reduce Four Integer Halfwords to Four Bytes

Reduce the precision of four integer halfwords to four byte values.

Description:

rd = sign_extend(rs23..16 || rs7..0 || rt23..16 || rt7..0)

The 8 least-significant bits from each of the two right-most integer halfword values in registers rs and rt are taken to produce four byte-sized results that are written to the four right-most byte elements in destination register rd. The two bytes values obtained from rs are written to the two left-most destination byte elements, and the two bytes obtained from rt are written to the two right-most destination byte elements.

The sign of the left-most byte result is extended into the 32 most-significant bits of the destination register.

Restrictions:

No data-dependent exceptions are possible.

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

Operation:

tempD7..0 = GPR[rs]23..16
tempC7..0 = GPR[rs]7..0
tempB7..0 = GPR[rt]23..16
tempA7..0 = GPR[rt]7..0
GPR[rd]63..0 = (tempD7)32 || tempD7..0 || tempC7..0 || tempB7..0 || tempA7..0

Exceptions:

Reserved Instruction, DSP Disabled