arm-elf-as truncates branch offsets w/o warning

[Nick Clifton]

Hi Alan,

: > +       /* Sign-extend a 24-bit number.  */
: > + #define SEXT24(x)	((((x) & 0xffffff) ^ (~ 0x7fffff)) + 0x800000)
: > + 
: 
: Hi Nick,
:    That looks wrong.  Don't you mean
: 
: #define SEXT24(x)	((((x) & 0xffffff) ^ 0x800000) - 0x800000)
:                                                      ^
: >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>^

No, the plus and the inversion are right.

Here are a couple of examples:

   x: 0xf7f00000     x:  0xf7700000
   &  0x00ffffff     &   0x00ffffff
   -------------     --------------
      0x00f00000         0x00700000
   ^  0xff800000     ^   0xff800000
   -------------     --------------
      0xff700000         0xfff00000
   +  0x00800000     +   0x00800000
   -------------     --------------
      0xfff00000         0x00700000

This method works regardless of the size of the host's word, (well
assuming that it is at least 32 bits anyway).

Cheers
	Nick