[PATCH] combine: Fix PR80233

[Jeff Law]

On 03/29/2017 02:44 PM, Jakub Jelinek wrote:
> On Wed, Mar 29, 2017 at 02:35:32PM -0600, Jeff Law wrote:
>> On 03/29/2017 12:23 PM, Segher Boessenkool wrote:
>>> If combine has added an unconditional trap there will be a new basic
>>> block as well.  It will then end up considering the NOTE_INSN_BASIC_BLOCK
>>> as the last_combined_insn, but then it tries to take the DF_INSN_LUID
>>> of that and that dereferences a NULL pointer (since such a note is not
>>> an INSN_P).
>>>
>>> This fixes it by not taking non-insns as last_combined_insn.
>>>
>>> Bootstrapped and tested on powerpc64-linux {-m32,-m64}.
>>>
>>>
>>> Segher
>>>
>>>
>>> 2017-03-29  Segher Boessenkool  <segher@kernel.crashing.org>
>>>
>>> 	PR rtl-optimization/80233
>>> 	* combine.c (combine_instructions): Only take NONDEBUG_INSN_P insns
>>> 	as last_combined_insn.  Do not test for BARRIER_P separately.
>>>
>>> gcc/testsuite/
>>> 	PR rtl-optimization/80233
>>> 	* gcc.c-torture/compile/pr80233.c: New testcase.
>> No strong opinions on this vs Jakub's patch.  I guess yours may walk more
>> objects on the chain, but in doing so is more likely to find a useful
>> LAST_COMBINED_INSN.  Jakub's stops earlier, but is less likely to have
>> stopped on something useful.
>>
>> Your call Segher.
>
> I like Segher's latest patch.  But it is his call anyway ;)
In that case let's just go with Segher's patch :-)

jeff