HADDPS (Packed Single-FP Horizontal Add)

Opcodes

Opcode/Instruction Op/En 64/32-bit Mode CPUID Feature Flag Description
F2 0F 7C /r HADDPS xmm1, xmm2/m128 RM V/V SSE3 Horizontal add packed single-precision floating-point values from xmm2/m128 to xmm1.
VEX.NDS.128.F2.0F.WIG 7C /r VHADDPS xmm1, xmm2, xmm3/m128 RVM V/V AVX Horizontal add packed single-precision floating-point values from xmm2 and xmm3/mem.
VEX.NDS.256.F2.0F.WIG 7C /r VHADDPS ymm1, ymm2, ymm3/m256 RVM V/V AVX Horizontal add packed single-precision floating-point values from ymm2 and ymm3/mem.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
RM ModRM:reg (r, w) ModRM:r/m (r) NA NA
RVM ModRM:reg (w) VEX.vvvv (r) ModRM:r/m (r) NA

Description

Adds the single-precision floating-point values in the first and second dwords of the destination operand and stores the result in the first dword of the destination operand.

Adds single-precision floating-point values in the third and fourth dword of the destination operand and stores the result in the second dword of the destination operand.

Adds single-precision floating-point values in the first and second dword of the source operand and stores the result in the third dword of the destination operand.

Adds single-precision floating-point values in the third and fourth dword of the source operand and stores the result in the fourth dword of the destination operand.

In 64-bit mode, use of the REX.R prefix permits this instruction to access additional registers (XMM8-XMM15).

See Figure 3-17 for HADDPS; see Figure 3-18 for VHADDPS.

Figure 3-17. HADDPS—Packed Single-FP Horizontal Add

X7

X6

X5

X4

X3

X2

X1

X0

SRC1

Y7

Y6

Y5

Y4

Y3

Y2

Y1

Y0

SRC2

DEST

Y6+Y7

Y4+Y5

X6+X7

X4+X5

Y2+Y3

Y0+Y1

X2+X3

X0+X1

Figure 3-18. VHADDPS operation

128-bit Legacy SSE version: The second source can be an XMM register or an 128-bit memory location. The desti-nation is not distinct from the first source XMM register and the upper bits (VLMAX-1:128) of the corresponding YMM register destination are unmodified.

VEX.128 encoded version: the first source operand is an XMM register or 128-bit memory location. The destination operand is an XMM register. The upper bits (VLMAX-1:128) of the corresponding YMM register destination are zeroed.

VEX.256 encoded version: The first source operand is a YMM register. The second source operand can be a YMM register or a 256-bit memory location. The destination operand is a YMM register.

Operation

HADDPS (128-bit Legacy SSE 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[VLMAX-1:128] (Unmodified)

VHADDPS (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[VLMAX-1:128] ← 0

VHADDPS (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 Equivalent

HADDPS:

__m128 _mm_hadd_ps (__m128 a, __m128 b);

VHADDPS:

__m256 _mm256_hadd_ps (__m256 a, __m256 b);

Exceptions

When the source operand is a memory operand, the operand must be aligned on a 16-byte boundary or a general-protection exception (#GP) will be generated.

Numeric Exceptions

Overflow, Underflow, Invalid, Precision, Denormal.

Other Exceptions

See Exceptions Type 2.