Emit DWARF3 call frame information when DWARF3+ debug info is requested

Oliver Stannard oliver.stannard at arm.com
Thu Jun 5 01:27:25 PDT 2014


http://reviews.llvm.org/D4027

Oliver

-----Original Message-----
From: David Blaikie [mailto:dblaikie at gmail.com] 
Sent: 04 June 2014 18:45
To: Oliver Stannard
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: Emit DWARF3 call frame information when DWARF3+ debug info is requested

Could you send this out from Phabricator? It's a bit easier to review
that way. (though I'm no CFI expert, so I'm probably not the person to
sign off on this, but I've a few bits of feedback)

On Wed, Jun 4, 2014 at 9:18 AM, Oliver Stannard <oliver.stannard at arm.com> wrote:
> Hi all,
>
> Currently, llvm always emits a DWARF CIE with a version of 1, even when
> emitting DWARF 3 or 4, which both support CIE version 3. This patch makes it
> emit the newer CIE version when we are emitting DWARF 3 or 4. This will not
> reduce compatibility, as we already emit other DWARF3/4 features, and is
> worth doing as the DWARF3 spec removed some ambiguities in the
> interpretation of call frame information.
>
> It also fixes a minor bug where the "return address" field of the CIE was
> encoded as a ULEB128, which is only valid when the CIE version is 3. There
> are no test changes for this, because (as far as I can tell) none of the
> platforms that we test have a return address register with a DWARF register
> number >127.
>
> Thanks,
> Oliver
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