# Conversion Intrinsics

Intel® Streaming SIMD Extensions 2 (Intel® SSE2) intrinsics for floating-point conversion operations are listed in this topic. The prototypes for Intel® SSE2 intrinsics are in the emmintrin.h header file.

To use these intrinsics, include the immintrin.h file as follows:

    #include <immintrin.h>

Each conversion intrinsic takes one data type and performs a conversion to a different type. Some conversions, such as those performed by the _mm_cvtpd_ps intrinsic, result in a loss of precision. The rounding mode used in such cases is determined by the value in the MXCSR register. The default rounding mode is round-to-nearest.

### Note

The rounding mode used by the C and C++ languages when performing a type conversion is to truncate. The `_mm_cvttpd_epi32` and `_mm_cvttsd_si32` intrinsics use the truncate rounding mode regardless of the mode specified by the MXCSR register.

The results of each intrinsic operation are placed in a register. The information about what is placed in each register appears in the tables below, in the detailed explanation for each intrinsic. For each intrinsic, the resulting register is represented by R, R0, R1, R2, and R3, where each represent the registers in which results are placed.

Intrinsic Name | Operation | Corresponding Intel® SSE2 Instruction
--- | --- | ---
_mm_cvtpd_ps | Convert DP FP to SP FP | CVTPD2PS
_mm_cvtps_pd | Convert from SP FP to DP FP | CVTPS2PD
_mm_cvtepi32_pd | Convert lower integer values to DP FP | CVTDQ2PD
_mm_cvtpd_epi32 | Convert DP FP values to integer values | CVTPD2DQ
_mm_cvtsd_si32 | Convert lower DP FP value to integer value | CVTSD2SI
_mm_cvtsd_ss | Convert lower DP FP value to SP FP | CVTSD2SS
_mm_cvtsi32_sd | Convert signed integer value to DP FP | CVTSI2SD
_mm_cvtss_sd | Convert lower SP FP value to DP FP | CVTSS2SD
_mm_cvttpd_epi32 | Convert DP FP values to signed integers | CVTTPD2DQ
_mm_cvttsd_si32 | Convert lower DP FP to signed integer | CVTTSD2SI
_mm_cvtpd_pi32 | Convert two DP FP values to signed integer values | CVTPD2PI
_mm_cvttpd_pi32 | Convert two DP FP values to signed integer values using truncate | CVTTPD2PI
_mm_cvtpi32_pd | Convert two signed integer values to DP FP | CVTPI2PD
_mm_cvtsd_f64 | Extract DP FP value from first vector element | None

## _mm_cvtpd_ps

__m128 _mm_cvtpd_ps(__m128d a);

Converts the two DP FP values of a to SP FP values.

R0 | R1 | R2 | R3
--- | --- | --- | ---
(float) a0 | (float) a1 | 0.0 | 0.0

## _mm_cvtps_pd

__m128d _mm_cvtps_pd(__m128 a);

Converts the lower two SP FP values of a to DP FP values.

R0 | R1
--- | ---
(double) a0 | (double) a1

## _mm_cvtepi32_pd

__m128d _mm_cvtepi32_pd(__m128i a);

Converts the lower two signed 32-bit integer values of a to DP FP values.

R0 | R1
--- | ---
(double) a0 | (double) a1

## _mm_cvtpd_epi32

__m128i _mm_cvtpd_epi32(__m128d a);

Converts the two DP FP values of a to 32-bit signed integer values.

R0 | R1 | R2 | R3
--- | --- | --- | ---
(int) a0 | (int) a1 | 0x0 | 0x0

## _mm_cvtsd_si32

int _mm_cvtsd_si32(__m128d a);

Converts the lower DP FP value of a to a 32-bit signed integer value.

R
(int) a0

## _mm_cvtsd_ss

__m128 _mm_cvtsd_ss(__m128 a, __m128d b);

Converts the lower DP FP value of b to an SP FP value. The upper SP FP values in a are passed through.

R0 | R1 | R2 | R3
--- | --- | --- | ---
(float) b0 | a1 | a2 | a3

## _mm_cvtsi32_sd

__m128d _mm_cvtsi32_sd(__m128d a, int b);

Converts the signed integer value in b to a DP FP value. The upper DP FP value in a is passed through.

R0 | R1
--- | ---
(double) b | a1

## _mm_cvtss_sd

__m128d _mm_cvtss_sd(__m128d a, __m128 b);

Converts the lower SP FP value of b to a DP FP value. The upper value DP FP value in a is passed through.

R0 | R1
--- | ---
(double) b0 | a1

## _mm_cvttpd_epi32

__m128i _mm_cvttpd_epi32(__m128d a);

Converts the two DP FP values of a to 32-bit signed integers using truncate.

R0 | R1 | R2 | R3
--- | --- | --- | ---
(int) a0 | (int) a1 | 0x0 | 0x0

## _mm_cvttsd_si32

int _mm_cvttsd_si32(__m128d a);

Converts the lower DP FP value of a to a 32-bit signed integer using truncate.

R
(int) a0

## _mm_cvtpd_pi32

__m64 _mm_cvtpd_pi32(__m128d a);

Converts the two DP FP values of a to 32-bit signed integer values.

R0 | R1
--- | ---
(int)a0 | (int) a1

## _mm_cvttpd_pi32

__m64 _mm_cvttpd_pi32(__m128d a);

Converts the two DP FP values of a to 32-bit signed integer values using truncate.

R0 | R1
--- | ---
(int)a0 | (int) a1

## _mm_cvtpi32_pd

__m128d _mm_cvtpi32_pd(__m64 a);

Converts the two 32-bit signed integer values of a to DP FP values.

R0 | R1
--- | ---
(double)a0 | (double)a1

## _mm_cvtsd_f64

double _mm_cvtsd_f64(__m128d a);

This intrinsic extracts a double precision floating point value from the first vector element of an `__m128d`. It does so in the most efficient manner possible in the context used.

### Note

This intrinsic does not map to any specific Intel® SSE2 instruction.

Parent topic: Floating-point Intrinsics