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Re: [RFC][PR middle-end/59285] builtin-unreachable-6 on ARM
- From: Joern Rennecke <joern dot rennecke at embecosm dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Steven Bosscher <stevenb dot gcc at gmail dot com>, GCC <gcc at gcc dot gnu dot org>
- Date: Tue, 26 Nov 2013 23:21:23 +0000
- Subject: Re: [RFC][PR middle-end/59285] builtin-unreachable-6 on ARM
- Authentication-results: sourceware.org; auth=none
- References: <5294F468 dot 1060006 at redhat dot com> <CABu31nP1mMa8FPBxsOb9scL9H3Q2NTznN3UETwEpSYiNLgEN=Q at mail dot gmail dot com> <52950CA2 dot 40607 at redhat dot com> <CABu31nOHRj7OYMdVqwRVuQPdphwCA6K2SGd2buY_e1foGaZUAg at mail dot gmail dot com> <52951B37 dot 4030305 at redhat dot com>
On 26 November 2013 22:05, Jeff Law <law@redhat.com> wrote:
> Open to other suggestions. The fundamental issue is BARRIERs live outside
> the CFG. So a pass that thinks it can manipulate the CFG and ignore the
> underlying RTL are going to have problems with things like this.
Here, the barrier itself acts like a JUMP_INSN with a special target -
a bit like return, except that our special destination here is
'unreachable'.
If you want to express this in the cfg other than having no successors, you
should have a special UNREACHABLE block, which thus becomes competition
for the exit block.