| Message ID | 4EF3894B.5050504@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 12/22/2011 11:47 AM, Aldy Hernandez wrote:
> + sorry ("non call exceptions and transactional memory are not supported");
Better worded as
transactional memory is not supported with non-call exceptions
Otherwise ok.
r~
On Thu, Dec 22, 2011 at 8:47 PM, Aldy Hernandez <aldyh@redhat.com> wrote: > The problem here is that with -fnon-call-exceptions, a memory dereference > may trap, but when we instrument the store, we have lost the landing pad > information. > > One solution would be to move the EH information to the TM load/store > instrumentation builtins, but that doesn't get us around the fact that > libitm is not exception safe, and we have no mechanism for taking and > exception (and propagating it) in the middle of a transaction. > > Richard has suggested that another alternative could be to support the > exception case for NULL, but non-null faulting memory references would still > cause a crash. In this case we would simply test for NULL at the start of > the accessors and explicitly throw the exception. > > And yet a third alternative, is to disable the -fgnu-tm and > -fnon-call-exceptions combination. I have implemented this one, as I'd > rather have it not work, than work half-way. > > Torvald, do you have any thoughts on the matter? > > Attached patch for disabling the feature, if you both agree on this > approach. I think this should be documented at the place -fgnu-tm is documented. Richard.
On 12/23/11 03:31, Richard Guenther wrote: > On Thu, Dec 22, 2011 at 8:47 PM, Aldy Hernandez<aldyh@redhat.com> wrote: >> The problem here is that with -fnon-call-exceptions, a memory dereference >> may trap, but when we instrument the store, we have lost the landing pad >> information. >> >> One solution would be to move the EH information to the TM load/store >> instrumentation builtins, but that doesn't get us around the fact that >> libitm is not exception safe, and we have no mechanism for taking and >> exception (and propagating it) in the middle of a transaction. >> >> Richard has suggested that another alternative could be to support the >> exception case for NULL, but non-null faulting memory references would still >> cause a crash. In this case we would simply test for NULL at the start of >> the accessors and explicitly throw the exception. >> >> And yet a third alternative, is to disable the -fgnu-tm and >> -fnon-call-exceptions combination. I have implemented this one, as I'd >> rather have it not work, than work half-way. >> >> Torvald, do you have any thoughts on the matter? >> >> Attached patch for disabling the feature, if you both agree on this >> approach. > > I think this should be documented at the place -fgnu-tm is documented. > > Richard. I can certainly do this. I am however, waiting for the final approval. It wasn't clear whether that was an approval from Richard Henderson, or whether I should wait for an official ok. OK for mainline?
On 01/04/2012 01:10 AM, Aldy Hernandez wrote: > I can certainly do this. I am however, waiting for the final approval. It wasn't clear whether that was an approval from Richard Henderson, or whether I should wait for an official ok. > > OK for mainline? Yes, it was approval. r~
Index: testsuite/g++.dg/tm/pr51212.C =================================================================== --- testsuite/g++.dg/tm/pr51212.C (revision 0) +++ testsuite/g++.dg/tm/pr51212.C (revision 0) @@ -0,0 +1,19 @@ +// { dg-do compile } +// { dg-options "-fgnu-tm -fnon-call-exceptions" } + +struct S +{ + S () + { + } +}; + +__attribute__ ((transaction_callable)) +void foo (int *p) +{ + S s; + if (*p) + ; +} + +// { dg-message "sorry, unimplemented: non call exceptions and transactional memory" "-fnon-call-exceptions and -fgnu-tm together" { target *-*-* } 0 } Index: opts.c =================================================================== --- opts.c (revision 182542) +++ opts.c (working copy) @@ -663,6 +663,9 @@ finish_options (struct gcc_options *opts opts->x_flag_toplevel_reorder = 0; } + if (opts->x_flag_tm && opts->x_flag_non_call_exceptions) + sorry ("non call exceptions and transactional memory are not supported"); + /* -Wmissing-noreturn is alias for -Wsuggest-attribute=noreturn. */ if (opts->x_warn_missing_noreturn) opts->x_warn_suggest_attribute_noreturn = true;