色婷婷AⅤ一区二区三区|亚洲精品第一国产综合亚AV|久久精品官方网视频|日本28视频香蕉

          新聞中心

          ARMv8指令學習(2)

          作者: 時間:2016-11-10 來源:網(wǎng)絡 收藏
          1. UXTB ---- Unsigned extend byte

          UXTB , 等同于 UBFM ,,#0,#7

          本文引用地址:http://cafeforensic.com/article/201611/317219.htm

          即:Wd = ZeroExtend(Wn<7:0>)

          從Wn中取出一個byte,賦給Wd,并把Wd的高3 bytes,用0填充。

          2. UXTH ---- Unsigned extend halfword

          UXTB , 等同于 UBFM ,,#0,#15

          即:Wd = ZeroExtend(Wn<15:0>)

          從Wn中取出2個byte,賦給Wd,并把Wd的高2 bytes,用0填充。

          3. Bitfield move指令
          (1) BFM : Bitfield move

          BFM Wd,Wn,#r,#s

          if (s>=r )

          Wd = Wn

          else

          Wd<32+s-r,32-r> = Wn

          同時:保持Wd中的其它bit不變
          (2)SBFM: Signed bitfield move

          SBFM Wd,Wn,#r,#s

          if (s>=r )

          Wd = Wn

          else

          Wd<32+s-r,32-r> = Wn

          并擴展相應的符號位.


          (3)UBFM:Unsignedbitfield move

          UBFM Wd,Wn,#r,#s

          if (s>=r )

          Wd = Wn

          else

          Wd<32+s-r,32-r> = Wn

          同時:設(shè)置Wd中的其它bit位為0

          4. Bitfield insert and extract指令
          (1) BFI : Bitfield insert

          BFI Wd, Wn, #lsb, #width

          等同于

          BFM Wd, Wn, #((32-lsb)&31) , #(width-1)

          即:

          width bits in Wd , starting at lsb , are replaced by width bits from Wn, starting at bit[0].

          Other bits in Rd are unchanged

          BFI指令,不會更改PSTATE中的flags


          (2) BFXIL : Bitfield extract and insert low

          BFXIL Wd, Wn, #lsb, #width
          等同于
          BFM Wd,Wn,#lsb,#(lsb+width-1)


          (3) SBFIZ : Signed bitfield insert in zero
          (4) SBFX : Signed bitfield extract
          (5) UBFIZ : Unsigned bitfield insert in zero
          (6) UBFX : Unsigned bitfield extract



          關(guān)鍵詞: ARMv8指令學

          評論


          技術(shù)專區(qū)

          關(guān)閉