# SQRTSD—Compute Square Root of Scalar Double-Precision Floating-Point Value

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

F2 0F 51 /*r*
SQRTSD *xmm1*, *xmm2/m64* |
RM |
V/V |
SSE2 |
Computes square root of the low double-precision floating-point value in *xmm2/m64 *and stores the results in *xmm1*. |

VEX.NDS.LIG.F2.0F.WIG 51/r
VSQRTSD* xmm1,xmm2, xmm3/m64* |
RVM |
V/V |
AVX |
Computes square root of the low double-precision floating point value in *xmm3/m64 *and stores the results in *xmm2*. Also, upper double precision floating-point value (bits[127:64]) from *xmm2* are copied to *xmm1*[127:64]. |

### 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 double-precision floating-point value in the source operand (second operand) and stores the double-precision floating-point result in the destination operand. The source operand can be an XMM register or a 64-bit memory location. The destination operand is an XMM register. The high quadword of the desti-nation operand remains unchanged. See Figure 11-4 in the *Intel® 64 and IA-32 Architectures Software Devel-oper’s Manual, Volume 1*, for an illustration of a scalar double-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 (VLMAX-1:64) of the corresponding YMM destination register remain unchanged.

VEX.128 encoded version: Bits (VLMAX-1:128) of the destination YMM register are zeroed.

## Operation

**SQRTSD (128-bit Legacy SSE version)**

DEST[63:0] ← SQRT(SRC[63:0])
DEST[VLMAX-1:64] (Unmodified)

**VSQRTSD (VEX.128 encoded version)**

DEST[63:0] ← SQRT(SRC2[63:0])
DEST[127:64] ← SRC1[127:64]
DEST[VLMAX-1:128] ← 0

## Intel C/C++ Compiler Intrinsic Equivalent

SQRTSD:

__m128d _mm_sqrt_sd (m128d a, m128d b)

## SIMD Floating-Point Exceptions

Invalid, Precision, Denormal.

## Other Exceptions

See Exceptions Type 3.