# CVTSD2SS—Convert Scalar Double-Precision FP Value to Scalar Single-Precision FP Value

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

F2 0F 5A /*r* CVTSD2SS *xmm1*, *xmm2/m64* |
RM |
V/V |
SSE2 |
Convert one double-precision floating-point value in *xmm2/m64 *to one single-precision floating-point value in *xmm1*. |

VEX.NDS.LIG.F2.0F.WIG 5A /r VCVTSD2SS xmm1,xmm2, xmm3/m64 |
RVM |
V/V |
AVX |
Convert one double-precision floating-point value in xmm3/m64 to one single-precision floating-point value and merge with high bits in 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 double-precision floating-point value in the source operand (second operand) to a single-precision floating-point value in the destination operand (first operand).

The source operand can be an XMM register or a 64-bit memory location. The destination operand is an XMM register. When the source operand is an XMM register, the double-precision floating-point value is contained in the low quadword of the register. The result is stored in the low doubleword of the destination operand, and the upper 3 doublewords are left unchanged. When the conversion is inexact, the value returned is rounded according to the rounding control bits in the MXCSR register.

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-1:32) 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

CVTSD2SS (128-bit Legacy SSE version)
DEST[31:0] ← Convert_Double_Precision_To_Single_Precision_Floating_Point(SRC[63:0]);
(* DEST[VLMAX-1:32] Unmodified *)
VCVTSD2SS (VEX.128 encoded version)
DEST[31:0] ← Convert_Double_Precision_To_Single_Precision_Floating_Point(SRC2[63:0]);
DEST[127:32] ← SRC1[127:32]
DEST[VLMAX-1:128] ← 0

## Intel C/C++ Compiler Intrinsic Equivalent

CVTSD2SS: |
__m128 _mm_cvtsd_ss(__m128 a, __m128d b) |

## SIMD Floating-Point Exceptions

Overflow, Underflow, Invalid, Precision, Denormal.

## Other Exceptions

See Exceptions Type 3.