raw
ffa_ch9_exodus.kv       1 ------------------------------------------------------------------------------
ffa_ch9_exodus.kv       2 ------------------------------------------------------------------------------
ffa_ch9_exodus.kv       3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
ffa_ch9_exodus.kv       4 --                                                                          --
ffa_ch9_exodus.kv       5 -- (C) 2018 Stanislav Datskovskiy ( www.loper-os.org )                      --
ffa_ch9_exodus.kv       6 -- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
ffa_ch9_exodus.kv       7 --                                                                          --
ffa_ch9_exodus.kv       8 -- You do not have, nor can you ever acquire the right to use, copy or      --
ffa_ch9_exodus.kv       9 -- distribute this software ; Should you use this software for any purpose, --
ffa_ch9_exodus.kv      10 -- or copy and distribute it to anyone or in any manner, you are breaking   --
ffa_ch9_exodus.kv      11 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
ffa_ch9_exodus.kv      12 -- continue doing so for the indefinite future. In any case, please         --
ffa_ch9_exodus.kv      13 -- always : read and understand any software ; verify any PGP signatures    --
ffa_ch9_exodus.kv      14 -- that you use - for any purpose.                                          --
ffa_ch9_exodus.kv      15 --                                                                          --
ffa_ch9_exodus.kv      16 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
ffa_ch9_exodus.kv      17 ------------------------------------------------------------------------------
ffa_ch9_exodus.kv      18 ------------------------------------------------------------------------------
ffa_ch9_exodus.kv      19 
ffa_ch9_exodus.kv      20 with W_Shifts; use W_Shifts;
ffa_ch9_exodus.kv      21 
ffa_ch9_exodus.kv      22 
ffa_ch9_exodus.kv      23 package body W_Mul is
ffa_ch9_exodus.kv      24    
ffa_ch10_karatsub...   25    function Mul_HalfWord_Iron(X : in HalfWord;
ffa_ch10_karatsub...   26                               Y : in HalfWord) return Word is
ffa_ch10_karatsub...   27    begin
ffa_ch10_karatsub...   28       return X * Y;
ffa_ch10_karatsub...   29    end Mul_HalfWord_Iron;
ffa_ch10_karatsub...   30    pragma Inline_Always(Mul_HalfWord_Iron);
ffa_ch10_karatsub...   31    
ffa_ch10_karatsub...   32    
ffa_ch9_exodus.kv      33    -- Multiply half-words X and Y, producing a Word-sized product
ffa_ch10_karatsub...   34    function Mul_HalfWord_Soft(X : in HalfWord; Y : in HalfWord) return Word is
ffa_ch9_exodus.kv      35       
ffa_ch9_exodus.kv      36       -- X-Slide
ffa_ch9_exodus.kv      37       XS : Word := X;
ffa_ch9_exodus.kv      38       
ffa_ch9_exodus.kv      39       -- Y-Slide
ffa_ch9_exodus.kv      40       YS : Word := Y;
ffa_ch9_exodus.kv      41       
ffa_ch9_exodus.kv      42       -- Gate Mask
ffa_ch9_exodus.kv      43       GM : Word;
ffa_ch9_exodus.kv      44       
ffa_ch9_exodus.kv      45       -- The Product
ffa_ch9_exodus.kv      46       XY : Word := 0;
ffa_ch9_exodus.kv      47       
ffa_ch9_exodus.kv      48       -- Performed for each bit of HalfWord's bitness:
ffa_ch9_exodus.kv      49       procedure Bit is
ffa_ch9_exodus.kv      50       begin
ffa_ch9_exodus.kv      51          
ffa_ch9_exodus.kv      52          -- Compute the gate mask
ffa_ch9_exodus.kv      53          GM := 0 - (YS and 1);
ffa_ch9_exodus.kv      54          
ffa_ch9_exodus.kv      55          -- Perform the gated addition
ffa_ch9_exodus.kv      56          XY := XY + (XS and GM);
ffa_ch9_exodus.kv      57          
ffa_ch9_exodus.kv      58          -- Crank the next Y-slide bit into position
ffa_ch9_exodus.kv      59          YS := Shift_Right(YS, 1);
ffa_ch9_exodus.kv      60          
ffa_ch9_exodus.kv      61          -- Advance the X-slide by 1 bit
ffa_ch9_exodus.kv      62          XS := Shift_Left(XS, 1);
ffa_ch9_exodus.kv      63          
ffa_ch9_exodus.kv      64       end Bit;
ffa_ch9_exodus.kv      65       pragma Inline_Always(Bit);
ffa_ch9_exodus.kv      66       
ffa_ch9_exodus.kv      67    begin
ffa_ch9_exodus.kv      68       
ffa_ch9_exodus.kv      69       -- For each bit of the Y-Slide (unrolled) :
ffa_ch9_exodus.kv      70       for b in 1 .. HalfByteness loop
ffa_ch9_exodus.kv      71          
ffa_ch9_exodus.kv      72          Bit; Bit; Bit; Bit; Bit; Bit; Bit; Bit;
ffa_ch9_exodus.kv      73          
ffa_ch9_exodus.kv      74       end loop;
ffa_ch9_exodus.kv      75       
ffa_ch9_exodus.kv      76       -- Return the Product
ffa_ch9_exodus.kv      77       return XY;
ffa_ch9_exodus.kv      78       
ffa_ch10_karatsub...   79    end Mul_HalfWord_Soft;
ffa_ch10_karatsub...   80    pragma Inline_Always(Mul_HalfWord_Soft);
ffa_ch9_exodus.kv      81    
ffa_ch9_exodus.kv      82    
ffa_ch9_exodus.kv      83    -- Get the bottom half of a Word
ffa_ch9_exodus.kv      84    function BottomHW(W : in Word) return HalfWord is
ffa_ch9_exodus.kv      85    begin
ffa_ch9_exodus.kv      86       return W and (2**HalfBitness - 1);
ffa_ch9_exodus.kv      87    end BottomHW;
ffa_ch9_exodus.kv      88    pragma Inline_Always(BottomHW);
ffa_ch9_exodus.kv      89    
ffa_ch9_exodus.kv      90    
ffa_ch9_exodus.kv      91    -- Get the top half of a Word
ffa_ch9_exodus.kv      92    function TopHW(W : in Word) return HalfWord is
ffa_ch9_exodus.kv      93    begin
ffa_ch9_exodus.kv      94       return Shift_Right(W, HalfBitness);
ffa_ch9_exodus.kv      95    end TopHW;
ffa_ch9_exodus.kv      96    pragma Inline_Always(TopHW);
ffa_ch9_exodus.kv      97    
ffa_ch9_exodus.kv      98    
ffa_ch9_exodus.kv      99    -- Carry out X*Y mult, return lower word XY_LW and upper word XY_HW.
ffa_ch9_exodus.kv     100    procedure Mul_Word(X       : in  Word;
ffa_ch9_exodus.kv     101                       Y       : in  Word;
ffa_ch9_exodus.kv     102                       XY_LW   : out Word;
ffa_ch9_exodus.kv     103                       XY_HW   : out Word) is
ffa_ch9_exodus.kv     104       
ffa_ch9_exodus.kv     105       -- Bottom half of multiplicand X
ffa_ch9_exodus.kv     106       XL : constant HalfWord := BottomHW(X);
ffa_ch9_exodus.kv     107       
ffa_ch9_exodus.kv     108       -- Top half of multiplicand X
ffa_ch9_exodus.kv     109       XH : constant HalfWord := TopHW(X);
ffa_ch9_exodus.kv     110       
ffa_ch9_exodus.kv     111       -- Bottom half of multiplicand Y
ffa_ch9_exodus.kv     112       YL : constant HalfWord := BottomHW(Y);
ffa_ch9_exodus.kv     113       
ffa_ch9_exodus.kv     114       -- Top half of multiplicand Y
ffa_ch9_exodus.kv     115       YH : constant HalfWord := TopHW(Y);
ffa_ch9_exodus.kv     116       
ffa_ch9_exodus.kv     117       -- XL * YL
ffa_ch10_karatsub...  118       LL : constant Word := Mul_HalfWord_Iron(XL, YL);
ffa_ch9_exodus.kv     119       
ffa_ch9_exodus.kv     120       -- XL * YH
ffa_ch10_karatsub...  121       LH : constant Word := Mul_HalfWord_Iron(XL, YH);
ffa_ch9_exodus.kv     122       
ffa_ch9_exodus.kv     123       -- XH * YL
ffa_ch10_karatsub...  124       HL : constant Word := Mul_HalfWord_Iron(XH, YL);
ffa_ch9_exodus.kv     125       
ffa_ch9_exodus.kv     126       -- XH * YH
ffa_ch10_karatsub...  127       HH : constant Word := Mul_HalfWord_Iron(XH, YH);
ffa_ch9_exodus.kv     128       
ffa_ch9_exodus.kv     129       -- Carry
ffa_ch9_exodus.kv     130       CL : constant Word := TopHW(TopHW(LL) + BottomHW(LH) + BottomHW(HL));
ffa_ch9_exodus.kv     131       
ffa_ch9_exodus.kv     132    begin
ffa_ch9_exodus.kv     133       
ffa_ch9_exodus.kv     134       -- Get the bottom half of the Product:
ffa_ch9_exodus.kv     135       XY_LW := LL + Shift_Left(LH + HL, HalfBitness);
ffa_ch9_exodus.kv     136       
ffa_ch9_exodus.kv     137       -- Get the top half of the Product:
ffa_ch9_exodus.kv     138       XY_HW := HH + TopHW(HL) + TopHW(LH) + CL;
ffa_ch9_exodus.kv     139       
ffa_ch9_exodus.kv     140    end Mul_Word;
ffa_ch9_exodus.kv     141    pragma Inline_Always(Mul_Word);
ffa_ch9_exodus.kv     142    
ffa_ch9_exodus.kv     143 end W_Mul;