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From: Robert Drehmel <robert@FreeBSD.org>
Date: Sun, 20 Oct 2002 15:50:14 -0700 (PDT)
To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: cvs commit: src/sys/dev/syscons sctermvar.h
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robert      2002/10/20 15:50:14 PDT

  Modified files:
    sys/dev/syscons      sctermvar.h 
  Log:
  Do not try to work around ``poor (un)sign extension code''
  creation by GCC-2.6.3.  Casting pointers to unsigned char
  to volatile pointers to unsigned char seemed to produce
  better results on the ia32 architecture with old versions
  of GCC.
  The current FreeBSD system compiler GCC-3.2.1 emits
  better sign extension code for non-volatile variables:
  
  volatile char c;
  int i = c;
  
  is compiled to:
  ...
  movb    -1(%ebp), %al
  movbsl  %al, %eax
  movl    %eax, -8(%ebp)
  ...
  
  char c;
  int i = c;
  
  is compiled to:
  ...
  movbsl  -1(%ebp), %eax
  movl    %eax, -8(%ebp)
  ...
  
  The same holds for zero-extension of dereferenced pointers
  to volatile unsigned char.
  When compiled on alpha or sparc64, the code produced for the
  two examples above does not differ.
  
  Revision  Changes    Path
  1.4       +2 -12     src/sys/dev/syscons/sctermvar.h

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