On 11/15/20 6:00 AM, J.W. Jagersma wrote:
> On 2020-11-12 16:51, Jeff Law wrote:
>> On 3/11/20 6:38 PM, J.W. Jagersma via Gcc-patches wrote:
>>> The following patch extends the generation of exception handling
>>> information, so that it is possible to catch exceptions thrown from
>>> volatile asm statements, when -fnon-call-exceptions is enabled. Parts
>>> of the gcc code already suggested this should be possible, but it was
>>> never fully implemented.
>>>
>>> Two new test cases are added. The target-dependent test should pass on
>>> platforms where throwing from a signal handler is allowed. The only
>>> platform I am aware of where that is the case is *-linux-gnu, so it is
>>> set to XFAIL on all others.
>>>
>>> gcc/
>>> 2020-03-11 Jan W. Jagersma <jwjager...@gmail.com>
>>>
>>> PR inline-asm/93981
>>> * tree-cfg.c (make_edges_bb): Make EH edges for GIMPLE_ASM.
>>> * tree-eh.c (lower_eh_constructs_2): Add case for GIMPLE_ASM.
>>> Assign register output operands to temporaries.
>>> * doc/extend.texi: Document that volatile asms can now throw.
>>>
>>> gcc/testsuite/
>>> 2020-03-11 Jan W. Jagersma <jwjager...@gmail.com>
>>>
>>> PR inline-asm/93981
>>> * g++.target/i386/pr93981.C: New test.
>>> * g++.dg/eh/pr93981.C: New test.
>> Is this the final version of the patch? Do we have agreement on the
>> sematics for output operands, particularly memory operands? The last
>> few messages in the March thread lead me to believe that's still not
>> settled.
>>
>>
>> Jeff
> Hi Jeff,
>
> From what I remember, no consensus was reached. The discussion didn't seem
> to be going anywhere, and I had found a suitable workaround, so the issue
> dropped off my radar. However this workaround now turned out to be somewhat
> fragile so I do hope to see this implemented in gcc someday.
>
> I'll have to check but I do think this is the "best" version I have of this
> patch. In my most recent branch here I changed all memory operands to inout,
> but I recall there being some problem with this. Anyway, as I think Richard
> said (most of this goes over my head), I think this is best left up to the
> user. If one expects their asm to throw they would also be smart enough to
> use the '+' modifier so that previous assignments are not optimized out.
I wouldn't expect that changing the memory operands to inout would
consistently work.
jeff
