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Date: Fri, 11 Oct 2002 13:20:00 -0000
From: Kevin Lawton <kevinlawton2001@yahoo.com>
Subject: Request of new __attribute__ for switch statements (elimination of the bounds check)
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X-SW-Source: 2002-10/txt/msg00622.txt.bz2

All,

For implementation of machine simulators, it's quite common
to have completely populated switch statements on byte values:

  unsigned char byte;

  switch (byte) {
    case 0:
    case 1:
    ...
    case 255:
    }

But I don't know of any way to tell the compiler to _not_ generate
a bounds check on the switch variable 'byte'.  All of the target
space is covered.

To solve this, could we add an attribute to switch?

  switch (byte) __attribute (( no-bounds-check )) {
    ...
    }

This would also be useful for cases, where it is known that
all possible targets are covered with case statements, yet
they don't appear to be fully populated to the compiler
(it's known only to the programmer that the logic prevents
certain values).

Thanks,
-Kevin

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