# RSQRTSS
# Compute Reciprocal of Square Root of Scalar Single- Precision Floating-Point Value
| Opcode | Mnemonic | Description |
|---|---|---|
| F3 0F 52 /r | RSQRTSS xmm1, xmm2/m32 | Computes the approximate reciprocal of the square root of the low single-precision floating-point value in xmm2/m32 and stores the results in xmm1. |
# Description
Computes an approximate reciprocal of the square root of the low single-precision floatingpoint value in the source operand (second operand) 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 RSQRTSS 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). When a source value is a negative value (other than -0.0), a floating-point indefinite is returned. 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 / SquareRoot(Source[0..31]));
//Destination[32..127] remains unchanged
2
3
| Instruction | Latency | Throughput | Execution Unit |
|---|---|---|---|
| CPUID | 0F3n/0F2n/069n | 0F3n/0F2n/069n | 0F2n |
| RSQRTSS xmm, xmm | 6/6/- | 4/4/1 | MMX_MISC MMX_SHFT |