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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 |
http://sourceware.org/bugzilla/show_bug.cgi?id=12848
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 ?
Cheers
Nick
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