tailieunhanh - ARM Architecture Reference Manual- P26

ARM Architecture Reference Manual- P26: The ARM instruction set architecture has evolved significantly since it was first developed, and will continue to be developed in the future. In order to be precise about which instructions exist in any particular ARM implementation, five major versions of the instruction set have been defined to date. | VFP Addressing Modes Scalar operations If the destination register lies in the first bank of eight registers the instruction specifies a scalar operation if d_bank 0 then vec_len 1 Sd 0 d_num Sn 0 n_num Sm 0 m_num Note Source operands The source operands are always scalars regardless of which bank they are in. This allows individual elements of vectors to be used as scalars. ARM DDI 0100E Copyright 1996-2000 ARM Limited. All rights reserved. C5-5 VFP Addressing Modes Mixed vector scalar operations If the destination register specified in the instruction does not lie in the first bank of eight registers but the second source register does then the destination register and first source register specify vectors and the second source register specifies a scalar if d_bank 0 and m_bank 0 then vec_len vector length specified by FPSCR for i 0 to vec_len-1 Sd i d_bank 3 d_index Sn i n_bank 3 n_index Sm i m_num d_index d_index vector stride specified by FPSCR if d_index 7 then d_index d_index - 8 n_index n_index vector stride specified by FPSCR if n_index 7 then n index n index - 8 Notes First source operand The first operand is always a vector regardless of which bank it is in. This allows a set of consecutive registers in the first bank to be treated as a vector. Vector wrap-around A vector operand must not wrap around so that it re-uses its first element. Otherwise the results of the instruction are UNPREDICTABLE. When the FPSCR specifies a vector stride of 1 this is not a restriction because the vector length is at most 8. When the FPSCR specifies a vector stride of 2 it implies that the vector length must be at most 4. Operand overlap If two operands overlap they must be identical both in terms of which registers are accessed and the order in which they are accessed. Otherwise the results of the instruction are UNPREDICTABLE. This implies that If the set of register numbers generated in Sd i overlaps the set of register numbers generated in Sn i then d_num .

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