PFRSQRT
Usage: PFRSQRT dest,src Modifies flags: None
Returns a low-precision estimate of the reciprocal square root of the source operand. The single result value is duplicated in both high and low halves of this instruction's 64-bit result.
Packed Single-Precision FP Reciprocal Square Root Approximation
PFRSQRT mm1,mm2/m64 ; 0F 0F /r 97 [PENT,3DNOW]
PFRSQRT performs a low precision estimate of the reciprocal square root of the low-order single-precision FP value in the source operand, storing the result in both halves of the destination register. The result is accurate to 15 bits. Negative operands are treated as positive operands for purposes of reciprocal square root computation, with the sign of the result the same as the sign of the source operand.
For higher precision reciprocals, this instruction should be followed by two more instructions: PFRSQIT1 and PFRCPIT2. This will result in a 24-bit accuracy. For more details, see the AMD 3DNow! technology manual.
EXAMPLE:
pfrsqrt mm1 mm2
PFRSQRT
Usage: PFRSQRT dest,src Modifies flags: None
Returns a low-precision estimate of the reciprocal square root of the source operand. The single result value is duplicated in both high and low halves of this instruction's 64-bit result.
Packed Single-Precision FP Reciprocal Square Root Approximation
PFRSQRT mm1,mm2/m64 ; 0F 0F /r 97 [PENT,3DNOW]
PFRSQRT performs a low precision estimate of the reciprocal square root of the low-order single-precision FP value in the source operand, storing the result in both halves of the destination register. The result is accurate to 15 bits. Negative operands are treated as positive operands for purposes of reciprocal square root computation, with the sign of the result the same as the sign of the source operand.
For higher precision reciprocals, this instruction should be followed by two more instructions: PFRSQIT1 and PFRCPIT2. This will result in a 24-bit accuracy. For more details, see the AMD 3DNow! technology manual.
EXAMPLE:
pfrsqrt mm1 mm2
PFRSQRT
Usage: PFRSQRT dest,src Modifies flags: None
Returns a low-precision estimate of the reciprocal square root of the source operand. The single result value is duplicated in both high and low halves of this instruction's 64-bit result.
Packed Single-Precision FP Reciprocal Square Root Approximation
PFRSQRT mm1,mm2/m64 ; 0F 0F /r 97 [PENT,3DNOW]
PFRSQRT performs a low precision estimate of the reciprocal square root of the low-order single-precision FP value in the source operand, storing the result in both halves of the destination register. The result is accurate to 15 bits. Negative operands are treated as positive operands for purposes of reciprocal square root computation, with the sign of the result the same as the sign of the source operand.
For higher precision reciprocals, this instruction should be followed by two more instructions: PFRSQIT1 and PFRCPIT2. This will result in a 24-bit accuracy. For more details, see the AMD 3DNow! technology manual.
EXAMPLE:
pfrsqrt mm1 mm2