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

## Opcodes

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.