PHADDW/PHADDD — Packed Horizontal Add

1. See note in Section 2.4, “AVX and SSE Instruction Exception Specification” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A and Section 22.25.3, “Exception Conditions of Legacy SIMD Instructions Operating on MMX Registers” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A.

Instruction Operand Encoding ¶

Description ¶

(V)PHADDW adds two adjacent 16-bit signed integers horizontally from the source and destination operands and packs the 16-bit signed results to the destination operand (first operand). (V)PHADDD adds two adjacent 32-bit signed integers horizontally from the source and destination operands and packs the 32-bit signed results to the destination operand (first operand). When the source operand is a 128-bit memory operand, the operand must be aligned on a 16-byte boundary or a general-protection exception (#GP) will be generated.

Note that these instructions can operate on either unsigned or signed (two’s complement notation) integers; however, it does not set bits in the EFLAGS register to indicate overflow and/or a carry. To prevent undetected overflow conditions, software must control the ranges of the values operated on.

Legacy SSE instructions: Both operands can be MMX registers. The second source operand can be an MMX register or a 64-bit memory location.

128-bit Legacy SSE version: The first source and destination operands are XMM registers. The second source operand can be an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the corresponding YMM destination register remain unchanged.

In 64-bit mode, use the REX prefix to access additional registers.

VEX.128 encoded version: The first source and destination operands are XMM registers. The second source operand can be an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the corresponding YMM register are zeroed.

VEX.256 encoded version: Horizontal addition of two adjacent data elements of the low 16-bytes of the first and second source operands are packed into the low 16-bytes of the destination operand. Horizontal addition of two adjacent data elements of the high 16-bytes of the first and second source operands are packed into the high 16-bytes of the destination operand. The first source and destination operands are YMM registers. The second source operand can be an YMM register or a 256-bit memory location.

Note: VEX.L must be 0, otherwise the instruction will #UD.

S7 S3 S3 S4 S3 S2 S1 S0

Operation ¶

PHADDW (with 64-bit operands) ¶

mm1[15-0] = mm1[31-16] + mm1[15-0];
mm1[31-16] = mm1[63-48] + mm1[47-32];
mm1[47-32] = mm2/m64[31-16] + mm2/m64[15-0];
mm1[63-48] = mm2/m64[63-48] + mm2/m64[47-32];

PHADDW (with 128-bit operands) ¶

xmm1[15-0] = xmm1[31-16] + xmm1[15-0];
xmm1[31-16] = xmm1[63-48] + xmm1[47-32];
xmm1[47-32] = xmm1[95-80] + xmm1[79-64];
xmm1[63-48] = xmm1[127-112] + xmm1[111-96];
xmm1[79-64] = xmm2/m128[31-16] + xmm2/m128[15-0];
xmm1[95-80] = xmm2/m128[63-48] + xmm2/m128[47-32];
xmm1[111-96] = xmm2/m128[95-80] + xmm2/m128[79-64];
xmm1[127-112] = xmm2/m128[127-112] + xmm2/m128[111-96];

VPHADDW (VEX.128 encoded version) ¶

DEST[15:0]←SRC1[31:16] + SRC1[15:0]
DEST[31:16]←SRC1[63:48] + SRC1[47:32]
DEST[47:32]←SRC1[95:80] + SRC1[79:64]
DEST[63:48]←SRC1[127:112] + SRC1[111:96]
DEST[79:64]←SRC2[31:16] + SRC2[15:0]
DEST[95:80]←SRC2[63:48] + SRC2[47:32]
DEST[111:96]←SRC2[95:80] + SRC2[79:64]
DEST[127:112]←SRC2[127:112] + SRC2[111:96]
DEST[MAXVL-1:128] ← 0

VPHADDW (VEX.256 encoded version) ¶

DEST[15:0]←SRC1[31:16] + SRC1[15:0]
DEST[31:16]←SRC1[63:48] + SRC1[47:32]
DEST[47:32]←SRC1[95:80] + SRC1[79:64]
DEST[63:48]←SRC1[127:112] + SRC1[111:96]
DEST[79:64]←SRC2[31:16] + SRC2[15:0]
DEST[95:80]←SRC2[63:48] + SRC2[47:32]
DEST[111:96]←SRC2[95:80] + SRC2[79:64]
DEST[127:112]←SRC2[127:112] + SRC2[111:96]
DEST[143:128]←SRC1[159:144] + SRC1[143:128]
DEST[159:144]←SRC1[191:176] + SRC1[175:160]
DEST[175:160]←SRC1[223:208] + SRC1[207:192]
DEST[191:176]←SRC1[255:240] + SRC1[239:224]
DEST[207:192]←SRC2[127:112] + SRC2[143:128]
DEST[223:208]←SRC2[159:144] + SRC2[175:160]
DEST[239:224]←SRC2[191:176] + SRC2[207:192]
DEST[255:240]←SRC2[223:208] + SRC2[239:224]

PHADDD (with 64-bit operands) ¶

mm1[31-0] = mm1[63-32] + mm1[31-0];
mm1[63-32] = mm2/m64[63-32] + mm2/m64[31-0];

PHADDD (with 128-bit operands) ¶

xmm1[31-0] = xmm1[63-32] + xmm1[31-0];
xmm1[63-32] = xmm1[127-96] + xmm1[95-64];
xmm1[95-64] = xmm2/m128[63-32] + xmm2/m128[31-0];
xmm1[127-96] = xmm2/m128[127-96] + xmm2/m128[95-64];

VPHADDD (VEX.128 encoded version) ¶

DEST[31-0]←SRC1[63-32] + SRC1[31-0]
DEST[63-32]←SRC1[127-96] + SRC1[95-64]
DEST[95-64]←SRC2[63-32] + SRC2[31-0]
DEST[127-96]←SRC2[127-96] + SRC2[95-64]
DEST[MAXVL-1:128] ← 0

VPHADDD (VEX.256 encoded version) ¶

DEST[31-0]←SRC1[63-32] + SRC1[31-0]
DEST[63-32]←SRC1[127-96] + SRC1[95-64]
DEST[95-64]←SRC2[63-32] + SRC2[31-0]
DEST[127-96]←SRC2[127-96] + SRC2[95-64]
DEST[159-128]←SRC1[191-160] + SRC1[159-128]
DEST[191-160]←SRC1[255-224] + SRC1[223-192]
DEST[223-192]←SRC2[191-160] + SRC2[159-128]
DEST[255-224]←SRC2[255-224] + SRC2[223-192]

Intel C/C++ Compiler Intrinsic Equivalents ¶

PHADDW: __m64 _mm_hadd_pi16 (__m64 a, __m64 b)

PHADDD: __m64 _mm_hadd_pi32 (__m64 a, __m64 b)

(V)PHADDW: __m128i _mm_hadd_epi16 (__m128i a, __m128i b)

(V)PHADDD: __m128i _mm_hadd_epi32 (__m128i a, __m128i b)

VPHADDW: __m256i _mm256_hadd_epi16 (__m256i a, __m256i b)

VPHADDD: __m256i _mm256_hadd_epi32 (__m256i a, __m256i b)

SIMD Floating-Point Exceptions ¶

None.

Other Exceptions ¶

See Exceptions Type 4; additionally