[llvm-commits] [patch]Fix for TableGen decoder generator

[Silviu Baranga]

Hi,

I've modified the patch to add a regression test
for this.

Because the break statement is missing, the ARM
ldrd instruction 0xd0000001 is decoded to a ldrsb
instruction instead of being undefined for
ARMv4. The 20th bit should be 1 for the
ldrsb instruction, which is not the case here.

Cheers,
Silviu

> -----Original Message-----
> From: David Blaikie [mailto:dblaikie at gmail.com]
> Sent: 30 March 2012 16:26
> To: Silviu Baranga
> Cc: llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm-commits] [patch]Fix for TableGen decoder generator
> 
> On Fri, Mar 30, 2012 at 2:04 AM, Silviu Baranga <silbar01 at arm.com>
> wrote:
> > Hi,
> >
> >
> >
> > TableGen's decoder generator does not add a break in the switch
> statements
> > for decoding structure's leaf nodes, because it considers that the
> leaf
> > nodes will always exit with a return. This is however not true for
> some
> > backends (for example the ARM backend) where we have to match
> multiple
> > architectures and an 'if' statement is generated to guard the leaf
> node.
> >
> >
> >
> > When failing the architecture check, without the break statement, the
> > decoder will incorrectly fall through to the next branch and match
> other
> > instructions that do  not correspond to the input bitpattern.
> >
> >
> >
> > The attached patch fixes this by making TableGen always emit a break
> > statement for leaf nodes.
> 
> Do you have a test case for the bug that exposed this?
> 
> >
> >
> >
> > Please review this patch.
> >
> >
> >
> > Thanks,
> >
> > Silviu
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >
-------------- next part --------------
A non-text attachment was scrubbed...
Name: tblgen.diff
Type: application/octet-stream
Size: 1627 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20120330/2ce9f0bb/attachment.obj>