In the x86 assembly programming language, MOVAPD is the name for a specific action performable by modern x86 processors with 2nd-generation Streaming SIMD Extensions (SSE2). This action involves copying a pair of numbers to temporary space in the processor for use in other computations. MOVAPD is one of the fastest ways to accomplish this effect - it is faster than the comparable instruction MOVSD.
Specifically, MOVAPD causes a 16-byte-aligned packed-doubles source to be copied to an XMM register or a 16-byte memory region.
Opcode | Assembly (Intel syntax) | Assembly (AT&T syntax) | icc intrinsic equivalent(s) | gcc built-in(s) |
---|---|---|---|---|
66 0F 28 /r | MOVAPD xmm1, xmm2/m128 | MOVAPD xmm2/m128, xmm1 | __m128 _mm_load_pd(double* p) | |
66 0F 29 /r | MOVAPD xmm1/m128, xmm2 | MOVAPD xmm2, xmm1/m128 | void _mm_store_pd(double* p, __m128 a) |
The source operand can be either an XMM register (xmm2) or a memory address (m128).
The destination operand can be either an XMM register (xmm1) or a memory address (m128). Note, however, that the source and destination operands cannot both be memory addresses.
If a memory address operand is not 16-byte-aligned, a general protection exception (#GP) will be raised. This can cause strange interoperability bugs when ordinary code calls an external code that was compiled with the assumption of a 16-byte-aligned stack frame boundary. [1]
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x86 is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. The 8086 was introduced in 1978 as a fully 16-bit extension of 8-bit Intel's 8080 microprocessor, with memory segmentation as a solution for addressing more memory than can be covered by a plain 16-bit address. The term "x86" came into being because the names of several successors to Intel's 8086 processor end in "86", including the 80186, 80286, 80386 and 80486. Colloquially, their names were "186", "286", "386" and "486".
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