# RCPSS
# Compute Reciprocal of Scalar Single-Precision Floating- Point Values
| Opcode | Mnemonic | Description |
|---|---|---|
| F3 0F 53 /r | RCPSS xmm1, xmm2/m32 | Compute the approximate reciprocal of the scalar single-precision floating-point value in xmm2/m32 and store the result in xmm1. |
# Description
Computes of an approximate reciprocal of the low single-precision floating-point value in the source operand (second operand) and stores the single-precision floating-point result in the destination operand. The source operand can be an XMM register or a 32-bit memory location.
The destination operand is an XMM register. The three high-order doublewords of the destination operand remain unchanged. See Figure 10-6 in the IA-32 Intel Architecture Software Developer's Manual, Volume 1 for an illustration of a scalar single-precision floating-point operation.
The relative error for this approximation is:
|Relative Error| <= 1.5 * 2-12 The RCPSS instruction is not affected by the rounding control bits in the MXCSR register.
When a source value is a 0.0, an infinite of the sign of the source value is returned. A denormal source value is treated as a 0.0 (of the same sign). Tiny results are always flushed to 0.0, with the sign of the operand. (Input values greater than or equal to |1.11111111110100000000000B2125| are guaranteed to not produce tiny results; input values less than or equal to |1.00000000000110000000001B2126| are guaranteed to produce tiny results, which are in turn flushed to 0.0; and input values in between this range may or may not produce tiny results, depending on the implementation.) When a source value is an SNaN or QNaN, the SNaN is converted to a QNaN or the source QNaN is returned.
# Operation
Destination[0..31] = Approximate(1.0 / Source[0..31]);
//Destination[32..127] remains unchanged
2
3
| Instruction | Latency | Throughput | Execution Unit |
|---|---|---|---|
| CPUID | 0F3n/0F2n/069n | 0F3n/0F2n/069n | 0F2n |
| RCPSS xmm, xmm | 6/6/1 | 2/2/1 | MMX_MISC MMX_SHFT |