sqrtsd

Square Root Scalar Double-Precision

SQRTSD xmm1, xmm2/m64

Computes square root of the low double.

Details

Computes the square root of the low 64-bit double-precision floating-point value in xmm2/m64 and stores the result in the low 64 bits of xmm1; the high 64 bits of xmm1 are set to zero. This operation follows IEEE 754 semantics and does not modify EFLAGS; negative operands produce NaN.

Pseudocode Operation

xmm1[0:63] ← FP64_sqrt(xmm2/m64[0:63])
xmm1[64:127] ← 0

Example

SQRTSD xmm1, xmm2/m64

Encoding

Binary Layout

Format SSE2

Opcode F2 0F 51

Extension SSE2

Operands

dest
128-bit XMM SIMD register
src
128-bit XMM SIMD register or Memory operand

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
F2 0F 51/r	SQRTSD xmm1,xmm2/m64	A	V/V	SSE2	Computes square root of the low double precision floatingpoint 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 floatingpoint 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 OR AVX10.1	Computes square root of the low double precision floatingpoint value in xmm3/m64 and stores the results in xmm1 under writemask k1. Also, upper double precision floatingpoint 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 writemask. Software should ensure VSQRTSD is encoded with VEX.L=0. Encoding VSQRTSD with VEX.L=1 may encounter unpredictable behavior across different processor generations. SQRTSD—Compute Square Root of Scalar Double Precision Floating-Point Value Vol. 2B 4-666

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)

Exceptions

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 2-49, “Type E3 Class Exception Conditions.” SQRTSD—Compute Square Root of Scalar Double Precision Floating-Point Value Vol. 2B 4-667