arch/m68k-mac/libgcc1/_truncdfsf2.s

   1 | double float to single float conversion routine
   2 |
   3 | written by Kai-Uwe Bloem (I5110401@dbstu1.bitnet).
   4 | Based on a 80x86 floating point packet from comp.os.minix, written by P.Housel
   5 |
   6 |
   7 | Revision 1.2, kub 01-90 :
   8 | added support for denormalized numbers
   9 |
  10 | Revision 1.1, kub 12-89 :
  11 | Ported over to 68k assembler
  12 |
  13 | Revision 1.0:
  14 | original 8088 code from P.S.Housel
  15
  16 BIAS4   =       0x7F-1
  17 BIAS8   =       0x3FF-1
  18
  19         .text
  20         .even
  21         .globl  __truncdfsf2
  22
  23 __truncdfsf2:
  24         lea     %sp@(4),%a0     | parameter pointer
  25         moveml  %d2-%d5,%sp@-   | save regs
  26         moveml  %a0@,%d4-%d5    | get number
  27
  28         movew   %a0@,%d0                | extract exponent
  29         movew   %d0,%d2         | extract sign
  30         lsrw    #4,%d0
  31         andw    #0x7ff,%d0      | kill sign bit
  32
  33         andl    #0x0fffff,%d4   | remove exponent from mantissa
  34         tstw    %d0             | check for zero exponent - no leading "1"
  35         beq     L_0             | for denormalized numbers
  36         orl     #0x100000,%d4   | restore implied leading "1"
  37         bra     L_1
  38 L_0:    addw    #1,%d0          | "normalize" exponent
  39 L_1:
  40         addw    #BIAS4-BIAS8,%d0        | adjust bias
  41
  42         addl    %d5,%d5         | shift up to realign mantissa for floats
  43         addxl   %d4,%d4
  44         addl    %d5,%d5
  45         addxl   %d4,%d4
  46         addl    %d5,%d5
  47         addxl   %d4,%d4
  48
  49         movel   %d5,%d1         | set rounding bits
  50         roll    #8,%d1
  51         andl    #0x00ffffff,%d5 | check to see if sticky bit should be set
  52         beq     L_2
  53         orb     #1,%d1          | set sticky bit
  54 L_2:
  55         jmp     norm_sf         | (leave regs on stack for norm_sf)