blendvps

Variable Blend Packed Single

BLENDVPS xmm1, xmm2/m128, <XMM0>

Blends floats based on variable mask in XMM0.

Details

Blends two packed single-precision floating-point values in XMM registers or memory based on per-lane sign bits of an implicit mask in XMM0; for each 32-bit lane, if the sign bit is 1, the value from the second source is selected, otherwise from the first source. Part of SSE4.1; no flags are affected. The result is stored in the first source operand (xmm1).

Pseudocode Operation

for i = 0 to 3 {
  if (XMM0.dword[i] < 0) {
    xmm1.float[i] ← src1.float[i];
  } else {
    xmm1.float[i] ← xmm1.float[i];
  }
}

Example

BLENDVPS xmm1, xmm2/m128, <XMM0>

Encoding

Binary Layout

Format SSE4.1

Opcode 66 0F 38 14

Extension SSE4.1

Operands

dest
128-bit XMM SIMD register
src1
128-bit XMM SIMD register or Memory operand
src2
Implicit XMM0 register (blend control mask)

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	64/32-bit Mode	CPUID	Description
66 0F 38 14 /r	BLENDVPS xmm1, xmm2/m128, <XMM0>	V/V	RM0 SSE4_1	Select packed single precision floating-point values from xmm1 and xmm2/m128 from mask specified in XMM0 and store the values into xmm1.
VEX.128.66.0F3A.W0 4A /r /is4	VBLENDVPS xmm1, xmm2, xmm3/m128, xmm4		AVX	RVMR V/V Conditionally copy single precision floating-point values from xmm2 or xmm3/m128 to xmm1, based on mask bits in the specified mask operand, xmm4.
VEX.256.66.0F3A.W0 4A /r /is4	VBLENDVPS ymm1, ymm2, ymm3/m256, ymm4		AVX	RVMR V/V Conditionally copy single precision floating-point values from ymm2 or ymm3/m256 to ymm1, based on mask bits in the specified mask register, ymm4.

Description

Conditionally copy each dword data element of single precision floating-point value from the second source operand and the first source operand depending on mask bits defined in the mask register operand. The mask bits are the most significant bit in each dword element of the mask register. Each quadword element of the destination operand is copied from: • the corresponding dword element in the second source operand, if a mask bit is “1”; or • the corresponding dword element in the first source operand, if a mask bit is “0”. The register assignment of the implicit mask operand for BLENDVPS is defined to be the architectural register XMM0. 128-bit Legacy SSE version: The first source operand and the destination operand is the same. Bits (MAXVL-1:128) of the corresponding YMM destination register remain unchanged. The mask register operand is implicitly defined to be the architectural register XMM0. An attempt to execute BLENDVPS with a VEX prefix will cause #UD. VEX.128 encoded version: The first source operand and the destination operand are XMM registers. The second source operand is an XMM register or 128-bit memory location. The mask operand is the third source register, and encoded in bits[7:4] of the immediate byte(imm8). The bits[3:0] of imm8 are ignored. In 32-bit mode, imm8[7] is ignored. The upper bits (MAXVL-1:128) of the corresponding YMM register (destination register) are zeroed. VEX.W must be 0, otherwise, the instruction will #UD. VEX.256 encoded version: The first source operand and destination operand are YMM registers. The second source operand can be a YMM register or a 256-bit memory location. The mask operand is the third source register, and encoded in bits[7:4] of the immediate byte(imm8). The bits[3:0] of imm8 are ignored. In 32-bit mode, imm8[7] is ignored. VEX.W must be 0, otherwise, the instruction will #UD. VBLENDVPS permits the mask to be any XMM or YMM register. In contrast, BLENDVPS treats XMM0 implicitly as the mask and do not support non-destructive destination operation. BLENDVPS—Variable Blend Packed Single Precision Floating-Point Values Vol. 2A 3-84

Operation

BLENDVPS (128-bit Legacy SSE Version)
MASK := XMM0
IF (MASK[31] = 0) THEN DEST[31:0] := DEST[31:0]
ELSE DEST [31:0] := SRC[31:0] FI
IF (MASK[63] = 0) THEN DEST[63:32] := DEST[63:32]
ELSE DEST [63:32] := SRC[63:32] FI
IF (MASK[95] = 0) THEN DEST[95:64] := DEST[95:64]
ELSE DEST [95:64] := SRC[95:64] FI
IF (MASK[127] = 0) THEN DEST[127:96] := DEST[127:96]
ELSE DEST [127:96] := SRC[127:96] FI
DEST[MAXVL-1:128] (Unmodified)

VBLENDVPS (VEX.128 Encoded Version)
MASK := SRC3
IF (MASK[31] = 0) THEN DEST[31:0] := SRC1[31:0]
ELSE DEST [31:0] := SRC2[31:0] FI
IF (MASK[63] = 0) THEN DEST[63:32] := SRC1[63:32]
ELSE DEST [63:32] := SRC2[63:32] FI
IF (MASK[95] = 0) THEN DEST[95:64] := SRC1[95:64]
ELSE DEST [95:64] := SRC2[95:64] FI
IF (MASK[127] = 0) THEN DEST[127:96] := SRC1[127:96]
ELSE DEST [127:96] := SRC2[127:96] FI
DEST[MAXVL-1:128] := 0

VBLENDVPS (VEX.256 Encoded Version)
MASK := SRC3
IF (MASK[31] = 0) THEN DEST[31:0] := SRC1[31:0]
ELSE DEST [31:0] := SRC2[31:0] FI
IF (MASK[63] = 0) THEN DEST[63:32] := SRC1[63:32]
ELSE DEST [63:32] := SRC2[63:32] FI
IF (MASK[95] = 0) THEN DEST[95:64] := SRC1[95:64]
ELSE DEST [95:64] := SRC2[95:64] FI
IF (MASK[127] = 0) THEN DEST[127:96] := SRC1[127:96]
ELSE DEST [127:96] := SRC2[127:96] FI
IF (MASK[159] = 0) THEN DEST[159:128] := SRC1[159:128]
ELSE DEST [159:128] := SRC2[159:128] FI
IF (MASK[191] = 0) THEN DEST[191:160] := SRC1[191:160]
ELSE DEST [191:160] := SRC2[191:160] FI
IF (MASK[223] = 0) THEN DEST[223:192] := SRC1[223:192]
ELSE DEST [223:192] := SRC2[223:192] FI
IF (MASK[255] = 0) THEN DEST[255:224] := SRC1[255:224]
ELSE DEST [255:224] := SRC2[255:224] FI

Intel C/C++ Compiler Intrinsic Equivalent

BLENDVPS __m128 _mm_blendv_ps(__m128 v1, __m128 v2, __m128 v3);
VBLENDVPS __m128 _mm_blendv_ps (__m128 a, __m128 b, __m128 mask);
VBLENDVPS __m256 _mm256_blendv_ps (__m256 a, __m256 b, __m256 mask);

Exceptions

SIMD Floating-Point Exceptions

None. BLENDVPS—Variable Blend Packed Single Precision Floating-Point Values Vol. 2A 3-85

Other Exceptions

See Table 2-21, “Type 4 Class Exception Conditions,” additionally: #UD If VEX.W = 1. BLENDVPS—Variable Blend Packed Single Precision Floating-Point Values Vol. 2A 3-86