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

A

V/V

SSE2

Computes square root of the low double precision floating- point value in xmm2/m64 and stores the results in xmm1.

VEX.LIG.F2.0F.WIG 51/r VSQRTSD xmm1,xmm2, xmm3/m64

B

V/V

AVX

Computes square root of the low double precision floating- point value in xmm3/m64 and stores the results in xmm1. Also, upper double precision floating-point value (bits[127:64]) from xmm2 is copied to xmm1[127:64].

EVEX.LLIG.F2.0F.W1 51/r VSQRTSD xmm1 {k1}{z}, xmm2, xmm3/m64{er}

C

V/V

AVX512F

Computes square root of the low double precision floating- point value in xmm3/m64 and stores the results in xmm1 under writemask k1. Also, upper double precision floating- point value (bits[127:64]) from xmm2 is copied to xmm1[127:64].

Instruction Operand Encoding

Op/En

Tuple Type

Operand 1

Operand 2

Operand 3

Operand 4

A

N/A

ModRM:reg (w)

ModRM:r/m (r)

N/A

N/A

B

N/A

ModRM:reg (w)

VEX.vvvv (r)

ModRM:r/m (r)

N/A

C

Tuple1 Scalar

ModRM:reg (w)

EVEX.vvvv (r)

ModRM:r/m (r)

N/A

Description

Computes the square root of the low double precision floating-point value in the second source operand and stores the double precision floating-point result in the destination operand. The second source operand can be an XMM register or a 64-bit memory location. The first source and destination operands are XMM registers.

128-bit Legacy SSE version: The first source operand and the destination operand are the same. The quadword at bits 127:64 of the destination operand remains unchanged. Bits (MAXVL-1:64) of the corresponding destination register remain unchanged.

VEX.128 and EVEX encoded versions: Bits 127:64 of the destination operand are copied from the corresponding bits of the first source operand. Bits (MAXVL-1:128) of the destination register are zeroed.

EVEX encoded version: The low quadword element of the destination operand is updated according to the write- mask.

Software should ensure VSQRTSD is encoded with VEX.L=0. Encoding VSQRTSD with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation

VSQRTSD (EVEX Encoded Version) 

IF (EVEX.b = 1) AND (SRC2 *is register*)
   THEN
       SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(EVEX.RC);
   ELSE 
       SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(MXCSR.RC);
FI;
IF k1[0] or *no writemask*
   THEN    DEST[63:0] := SQRT(SRC2[63:0])
   ELSE 
       IF *merging-masking*                ; merging-masking
            THEN *DEST[63:0] remains unchanged*
            ELSE                            ; zeroing-masking
                THEN DEST[63:0] := 0
       FI;
FI;
DEST[127:64] := SRC1[127:64]
DEST[MAXVL-1:128] := 0

VSQRTSD (VEX.128 Encoded Version) 

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

SQRTSD (128-bit Legacy SSE Version) 

DEST[63:0] := SQRT(SRC[63:0])
DEST[MAXVL-1:64] (Unmodified)

Intel C/C++ Compiler Intrinsic Equivalent 

VSQRTSD __m128d _mm_sqrt_round_sd(__m128d a, __m128d b, int r);
VSQRTSD __m128d _mm_mask_sqrt_round_sd(__m128d s, __mmask8 k, __m128d a, __m128d b, int r);
VSQRTSD __m128d _mm_maskz_sqrt_round_sd(__mmask8 k, __m128d a, __m128d b, int r);
SQRTSD __m128d _mm_sqrt_sd (__m128d a, __m128d b)

SIMD Floating-Point Exceptions

Invalid, Precision, Denormal.

Other Exceptions

Non-EVEX-encoded instruction, see Table 2-20, "Type 3 Class Exception Conditions." EVEX-encoded instruction, see Table 2-47, "Type E3 Class Exception Conditions."