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[Bug gas/12848] ARM: Thumb-2: Range check on b.w is off by a factor of 2

From: nickc at redhat dot com
Subject: [Bug gas/12848] ARM: Thumb-2: Range check on b.w is off by a factor of 2
Date: Wed, 20 Jul 2011 09:57:34 +0000


Nick Clifton <nickc at redhat dot com> changed:

           What    |Removed                     |Added
             Status|REOPENED                    |WAITING

--- Comment #10 from Nick Clifton <nickc at redhat dot com> 2011-07-20 09:56:40 
UTC ---
Hi Dave,

  Thanks for the extended test case and revised patch.  Unfortunately there are
a couple of problems with this new patch which I hope you won't mind taking a
look at:

  1.  The assembler can still miss a badly aligned BLX instruction.  For
example try assembling the uploaded fred.s file and then disassembling the
result.  You should see this:

 2000006:       f400 f800       bl      1c0000a <f-0x3ffff6>
 200000a:       f3ff ffff       bl      240000c <g+0x3ffff0>
 200000e:       f400 e801                ; <UNDEFINED> instruction: 0xf400e801
 2000012:       f000 e000       blx     2400014 <g+0x3ffff8>

  2. The patch will reported mis-aligned branches as being out of range.

  3. For some reason, with some of the out of range branches we also get an
error message about trying to stuff a large value into a small bitfield. 
Ideally there should only be one error message per problem in the assembler
source file.

  4. There ought to be a proper set of test cases in the assembler testsuite to
check this sort of thing.

I have uploaded a revised version of your patch which is my attempt to address
points 2 and 4.  But points 1 and 3 still need investigating.  Would you mind
doing the honours ?


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