# SQRTSS—Compute Square Root of Scalar Single-Precision Floating-Point Value

Opcode*/Instruction |
Op/En |
64/32 bit Mode Support |
CPUID Feature Flag |
Description |

F3 0F 51 /*r* SQRTSS *xmm1*, *xmm2/m32* |
RM |
V/V |
SSE |
Computes square root of the low singleprecision floating-point value in *xmm2/m32* and stores the results in *xmm1.* |

VEX.NDS.LIG.F3.0F.WIG 51/r VSQRTSS *xmm1, xmm2, xmm3/m32* |
RVM |
V/V |
AVX |
Computes square root of the low singleprecision floating-point value in *xmm3/m32* and stores the results in *xmm1*. Also, upper single precision floating-point values (bits[127:32]) from *xmm2* are copied to *xmm1[127:32].* |

## Instruction Operand Encoding

Op/En |
Operand 1 |
Operand 2 |
Operand 3 |
Operand 4 |

RM |
ModRM:reg (w) |
ModRM:r/m (r) |
NA |
NA |

RVM |
ModRM:reg (w) |
VEX.vvvv (r) |
ModRM:r/m (r) |
NA |

## Description

Computes the square root 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 *Intel® 64 and IA-32 Architectures* *Software Developer’s Manual, Volume 1, for an illustration of a scalar single-precision floating-point operation.*

In 64-bit mode, using a REX prefix in the form of REX.R permits this instruction to access additional registers (XMM8-XMM15). 128-bit Legacy SSE version: The first source operand and the destination operand are the same. Bits (VLMAX1:32) of the corresponding YMM destination register remain unchanged. VEX.128 encoded version: Bits (VLMAX-1:128) of the destination YMM register are zeroed.

## Operation

SQRTSS (128-bit Legacy SSE version)
DEST[31:0] ← SQRT(SRC2[31:0])
DEST[VLMAX-1:32] (Unmodified)
VSQRTSS (VEX.128 encoded version)
DEST[31:0] ← SQRT(SRC2[31:0])
DEST[127:32] ← SRC1[127:32]
DEST[VLMAX-1:128] ← 0

## Intel C/C++ Compiler Intrinsic Equivalent

SQRTSS: |
__m128 _mm_sqrt_ss(__m128 a) |

## SIMD Floating-Point Exceptions

Invalid, Precision, Denormal.

## Other Exceptions

See Exceptions Type 3.