VEXPANDPS—Load Sparse Packed Single-Precision Floating-Point Values from Dense Memory

Opcode/

Op /

64/32

CPUID

Description

Instruction En bit Mode Support Feature Flag
EVEX.128.66.0F38.W0 88 /r VEXPANDPS xmm1 {k1}{z}, xmm2/m128 A V/V AVX512VL AVX512F Expand packed single-precision floating-point values from xmm2/m128 to xmm1 using writemask k1.
EVEX.256.66.0F38.W0 88 /r VEXPANDPS ymm1 {k1}{z}, ymm2/m256 A V/V AVX512VL AVX512F Expand packed single-precision floating-point values from ymm2/m256 to ymm1 using writemask k1.
EVEX.512.66.0F38.W0 88 /r VEXPANDPS zmm1 {k1}{z}, zmm2/m512 A V/V AVX512F Expand packed single-precision floating-point values from zmm2/m512 to zmm1 using writemask k1.

Instruction Operand Encoding

Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4
A Tuple1 Scalar ModRM:reg (w) ModRM:r/m (r) NA NA

Description

Expand (load) up to 16/8/4, contiguous, single-precision floating-point values of the input vector in the source operand (the second operand) to sparse elements of the destination operand (the first operand) selected by the writemask k1.

The destination operand is a ZMM/YMM/XMM register, the source operand can be a ZMM/YMM/XMM register or a 512/256/128-bit memory location.

The input vector starts from the lowest element in the source operand. The writemask k1 selects the destination elements (a partial vector or sparse elements if less than 16 elements) to be replaced by the ascending elements in the input vector. Destination elements not selected by the writemask k1 are either unmodified or zeroed, depending on EVEX.z.

EVEX.vvvv is reserved and must be 1111b otherwise instructions will #UD.

Note that the compressed displacement assumes a pre-scaling (N) corresponding to the size of one single element instead of the size of the full vector.

Operation

VEXPANDPS (EVEX encoded versions)

(KL, VL) = (4, 128), (8, 256), (16, 512)

k := 0

FOR j := 0 TO KL-1

i := j * 32

IF k1[j] OR *no writemask*

THEN

DEST[i+31:i] := SRC[k+31:k];

k := k + 32

ELSE

IF *merging-masking*

; merging-masking

THEN *DEST[i+31:i] remains unchanged*

ELSE

; zeroing-masking

DEST[i+31:i] := 0

FI

FI;

ENDFOR

DEST[MAXVL-1:VL] := 0

Intel C/C++ Compiler Intrinsic Equivalent

VEXPANDPS __m512 _mm512_mask_expand_ps( __m512 s, __mmask16 k, __m512 a);

VEXPANDPS __m512 _mm512_maskz_expand_ps( __mmask16 k, __m512 a);

VEXPANDPS __m512 _mm512_mask_expandloadu_ps( __m512 s, __mmask16 k, void * a);

VEXPANDPS __m512 _mm512_maskz_expandloadu_ps( __mmask16 k, void * a);

VEXPANDPD __m256 _mm256_mask_expand_ps( __m256 s, __mmask8 k, __m256 a);

VEXPANDPD __m256 _mm256_maskz_expand_ps( __mmask8 k, __m256 a);

VEXPANDPD __m256 _mm256_mask_expandloadu_ps( __m256 s, __mmask8 k, void * a);

VEXPANDPD __m256 _mm256_maskz_expandloadu_ps( __mmask8 k, void * a);

VEXPANDPD __m128 _mm_mask_expand_ps( __m128 s, __mmask8 k, __m128 a);

VEXPANDPD __m128 _mm_maskz_expand_ps( __mmask8 k, __m128 a);

VEXPANDPD __m128 _mm_mask_expandloadu_ps( __m128 s, __mmask8 k, void * a);

VEXPANDPD __m128 _mm_maskz_expandloadu_ps( __mmask8 k, void * a);

SIMD Floating-Point Exceptions

None

Other Exceptions

See Exceptions Type E4.nb in Table 2-49, “Type E4 Class Exception Conditions”; additionally:

#UD If EVEX.vvvv != 1111B.