RFR (XXS): 8026376: assert(false) failed: DEBUG MESSAGE: exception pc already set
christian.thalinger at oracle.com
Mon Oct 14 17:40:59 PDT 2013
On Oct 14, 2013, at 2:59 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
> For the record. Christian and I discussed it and decided to remove 'exception pc' load in deopt_blob on all platforms in separate changes. First, it is broken in x86 code anyway (it is not saved in all paths in deopt_blob). Second, we return into Interpreter which know nothing (and don't care) about compiled code and it does not use this pc data.
Right. So the fix is:
diff -r f50418dfb1b7 src/cpu/sparc/vm/sharedRuntime_sparc.cpp
--- a/src/cpu/sparc/vm/sharedRuntime_sparc.cpp Sun Oct 13 13:22:24 2013 -0700
+++ b/src/cpu/sparc/vm/sharedRuntime_sparc.cpp Mon Oct 14 17:35:02 2013 -0700
@@ -3581,6 +3581,7 @@ void SharedRuntime::generate_deopt_blob(
// the pending exception will be picked up the interpreter.
__ ld_ptr(G2_thread, in_bytes(JavaThread::exception_oop_offset()), Oexception);
__ st_ptr(G0, G2_thread, in_bytes(JavaThread::exception_oop_offset()));
+ __ st_ptr(G0, G2_thread, in_bytes(JavaThread::exception_pc_offset()));
// deallocate the deoptimization frame taking care to preserve the return values
Will file a bug for removing the load on all architectures.
> On 10/14/13 2:17 PM, Christian Thalinger wrote:
>> The reason I've added it is because we do it on x86 but there are comments like this:
>> // I think this is useless (throwing pc?)
>> __ movptr(rdx, Address(rsp, RegisterSaver::rdx_offset_in_bytes()));
>> So we either should read it everywhere or don't.
>> On Oct 14, 2013, at 11:43 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>> Don't read exception pc since it is not needed. You may trash a value in that register.
>>> On 10/14/13 11:19 AM, Christian Thalinger wrote:
>>>> 8026376: assert(false) failed: DEBUG MESSAGE: exception pc already set
>>>> It made me suspicious that only the second assert fired (the exception pc check) and not the first one (the exception oop check). I checked all the places where JavaThread::exception_oop_offset() was used to clear the exception oop to see if we also clear the exception pc.
>>>> In the deopt blob we have such a case. On x86 we clear both but on SPARC we don't.
>>>> Added the missing null-store instruction makes the test case pass.
>>>> Reading the exception pc is not really required but I've added it for completeness.
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