cvs commit: src/sys/boot/i386/btx/btx btx.S

[John Baldwin]

jhb         2006-10-05 15:30:51 UTC

  FreeBSD src repository

  Modified files:
    sys/boot/i386/btx/btx btx.S 
  Log:
  - Fix a couple of improper uses of leal in the previous space saving
    commits.  For some reason I thought the scale factor was a shift count
    rather than the multiplicand (that is, I thought leal (%eax,%edx,4) was
    going to generate %eax + %edx << 4 rather than %eax + %edx * 4).  What
    I need is to multiply by 16 to convert a real-mode (seg, offset) tuple
    into a flat address.  However, the max multiplicand for scaled/index
    addressing on i386 is 8, so go back to using a shl and an add.
  - Convert two more inter-register mov instructions where we don't need to
    preserve the source register to xchg instructions to keep our space
    savings.
  
  Tested by:      Ian FREISLICH if at hetzner.co.za
  MFC after:      1 week
  
  Revision  Changes    Path
  1.43      +7 -5      src/sys/boot/i386/btx/btx/btx.S