# CVTSS2SD—Convert Scalar Single-Precision FP Value to Scalar Double-Precision FP Value

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

F3 0F 5A /*r*
CVTSS2SD *xmm1*, *xmm2/m32* |
RM |
V/V |
SSE2 |
Convert one single-precision floating-point value in *xmm2/m32 *to one double-precision floating-point value in *xmm1*. |

VEX.NDS.LIG.F3.0F.WIG 5A /r
VCVTSS2SD xmm1, xmm2, xmm3/m32 |
RVM |
V/V |
AVX |
Convert one single-precision floating-point value in xmm3/m32 to one double-precision floating-point value and merge with high bits of xmm2. |

### 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

Converts a single-precision floating-point value in the source operand (second operand) to a double-precision floating-point value in the destination operand (first operand). The source operand can be an XMM register or a 32-bit memory location. The destination operand is an XMM register. When the source operand is an XMM register, the single-precision floating-point value is contained in the low doubleword of the register. The result is stored in the low quadword of the destination operand, and the high quadword is left unchanged.

In 64-bit mode, use of the REX.R prefix permits this instruction to access additional registers (XMM8-XMM15).

128-bit Legacy SSE version: The destination and first source operand are the same. Bits (VLMAX-1:64) of the corresponding YMM destination register remain unchanged.

VEX.128 encoded version: Bits (127:64) of the XMM register destination are copied from corresponding bits in the first source operand. Bits (VLMAX-1:128) of the destination YMM register are zeroed.

## Operation

**CVTSS2SD (128-bit Legacy SSE version)**

DEST[63:0] ← Convert_Single_Precision_To_Double_Precision_Floating_Point(SRC[31:0]);
DEST[VLMAX-1:64] (Unmodified)

**VCVTSS2SD (VEX.128 encoded version)**

DEST[63:0] ← Convert_Single_Precision_To_Double_Precision_Floating_Point(SRC2[31:0])
DEST[127:64] ← SRC1[127:64]
DEST[VLMAX-1:128] ← 0

## Intel C/C++ Compiler Intrinsic Equivalent

CVTSS2SD:

__m128d _mm_cvtss_sd(__m128d a, __m128 b)

## SIMD Floating-Point Exceptions

Invalid, Denormal.

## Other Exceptions

See Exceptions Type 3.