review (XS) for 6982533: Crash in ~StubRoutines::jbyte_fill with AggressiveOpts enabled

Tom Rodriguez tom.rodriguez at
Tue Sep 7 11:05:05 PDT 2010

On Sep 7, 2010, at 10:49 AM, Vladimir Kozlov wrote:

> Looks good but could we also check (in assert?) that address type is array pointer?

I considered adding that as an early check but I wanted an explicit check that we found the index to confirm the shape of the address expression.  I could add an early weed out test:

--- a/src/share/vm/opto/loopTransform.cpp       Fri Sep 03 13:31:03 2010 -0700                                                                       
+++ b/src/share/vm/opto/loopTransform.cpp       Tue Sep 07 11:04:07 2010 -0700                                                                       
@@ -2417,6 +2417,8 @@ bool PhaseIdealLoop::match_fill_loop(Ide
       Node* value = n->in(MemNode::ValueIn);                                                                                                         
       if (!lpt->is_invariant(value)) {                                                                                                               
         msg  = "variant store value";                                                                                                               
+      } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {                                                                               
+        msg = "not array address";                                                                                                                   
       store = n;                                                                                                                                     
       store_value = value; 


> Thanks,
> Vladimir
> Tom Rodriguez wrote:
>> 6982533: Crash in  ~StubRoutines::jbyte_fill with AggressiveOpts enabled
>> Reviewed-by:
>> The logic for matching a byte fill is missing a check for the use of
>> the index.  It normally happens as part of the check for a shift
>> expression but since a byte array doesn't have a shift the check is
>> missed.  The fix is to make the index check explicit.  The reason it
>> didn't always crash was because of differences in heap size caused by
>> ergonomics.  With a 16m heap it crashes on any machine.  Tested with
>> failing test case.
>> src/share/vm/opto/loopTransform.cpp

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