# CVTSS2SD — Convert Scalar Single Precision Floating-Point Value to Scalar Double PrecisionFloating-Point Value

Opcode/Instruction | Op / En | 64/32 bit Mode Support | CPUID Feature Flag | Description
--- | --- | --- | --- | ---
F3 0F 5A /r CVTSS2SD xmm1, xmm2/m32 | A | V/V | SSE2 | Convert one single precision floating-point value in xmm2/m32 to one double precision floating-point value in xmm1.
VEX.LIG.F3.0F.WIG 5A /r VCVTSS2SD xmm1, xmm2, xmm3/m32 | B | 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.
EVEX.LLIG.F3.0F.W0 5A /r VCVTSS2SD xmm1 {k1}{z}, xmm2, xmm3/m32{sae} | C | V/V | AVX512F | Convert one single precision floating-point value in xmm3/m32 to one double precision floating-point value and merge with high bits of xmm2 under writemask k1.

## Instruction Operand Encoding ¶

Op/En | Tuple Type | Operand 1 | Operand 2 | Operand 3 | Operand 4
--- | --- | --- | --- | --- | ---
A | N/A | ModRM:reg (r, 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 ¶

Converts a single precision floating-point value in the “convert-from” source operand to a double precision floating-point value in the destination operand. When the “convert-from” 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.

128-bit Legacy SSE version: The “convert-from” source operand (the second operand) is an XMM register or memory location. Bits (MAXVL-1:64) of the corresponding destination register remain unchanged. The destination operand is an XMM register.

VEX.128 and EVEX encoded versions: The “convert-from” source operand (the third operand) can be an XMM register or a 32-bit memory location. The first source and destination operands are XMM registers. Bits (127:64) of the XMM register destination are copied from the corresponding bits in the first source operand. Bits (MAXVL-1:128) of the destination register are zeroed.

Software should ensure VCVTSS2SD is encoded with VEX.L=0. Encoding VCVTSS2SD with VEX.L=1 may encounter unpredictable behavior across different processor generations.

## Operation ¶

### VCVTSS2SD (EVEX Encoded Version) ¶

    IF k1[0] or *no writemask*
        THEN DEST[63:0] := Convert_Single_Precision_To_Double_Precision_Floating_Point(SRC2[31:0]);
        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

### 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[MAXVL-1:128] := 0

### CVTSS2SD (128-bit Legacy SSE Version) ¶

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

## Intel C/C++ Compiler Intrinsic Equivalent ¶

    VCVTSS2SD __m128d _mm_cvt_roundss_sd(__m128d a, __m128 b, int r);

    VCVTSS2SD __m128d _mm_mask_cvt_roundss_sd(__m128d s, __mmask8 m, __m128d a,__m128 b, int r);

    VCVTSS2SD __m128d _mm_maskz_cvt_roundss_sd(__mmask8 k, __m128d a, __m128 a, int r);

    VCVTSS2SD __m128d _mm_mask_cvtss_sd(__m128d s, __mmask8 m, __m128d a,__m128 b);

    VCVTSS2SD __m128d _mm_maskz_cvtss_sd(__mmask8 m, __m128d a,__m128 b);

    CVTSS2SD __m128d_mm_cvtss_sd(__m128d a, __m128 a);

## SIMD Floating-Point Exceptions ¶

Invalid, Denormal.

## Other Exceptions ¶

VEX-encoded instructions, see Table 2-20, “Type 3 Class Exception Conditions.”

EVEX-encoded instructions, see Table 2-47, “Type E3 Class Exception Conditions.”