Intel 253666-024US - Manual (Page 481)

Vol. 2A 3-435
INSTRUCTION SET REFERENCE, A-M
HADDPD—Packed Double-FP Horizontal Add
HADDPD—Packed Double-FP Horizontal Add
Description
Adds the double-precision floating-point values in the high and low quadwords of the
destination operand and stores the result in the low quadword of the destination
operand.
Adds the double-precision floating-point values in the high and low quadwords of the
source operand and stores the result in the high quadword of the destination operand.
See Figure 3-10.
In 64-bit mode, use of the REX.R prefix permits this instruction to access additional
registers (XMM8-XMM15).
Opcode Instruction 64-Bit
Mode
Compat/
Leg Mode
Description
66 0F 7C /r HADDPD xmm1,
xmm2/m128
Valid Valid Horizontal add packed double-
precision floating-point values
from xmm2/m128 to xmm1.
Figure 3-10. HADDPD—Packed Double-FP Horizontal Add
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