[15] RFR(XS): 8239083: C1 assert(known_holder == NULL || (known_holder->is_instance_klass() && (!known_holder->is_interface() || ((ciInstanceKlass*)known_holder)->has_nonstatic_concrete_methods())), "should be non-static concrete method");

[Christian Hagedorn]

Hi

Please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8239083
http://cr.openjdk.java.net/~chagedorn/8239083/webrev.00/

The assert fails in the test case when invoking the only static 
interface method with a method handle. In this case, known_holder is 
non-NULL. However, known_holder would be set to NULL at [1] since the 
call returns NULL when known_holder is an interface.

In the failing test case, known_holder is non-NULL since 
GraphBuilder::try_method_handle_inline() calls 
GraphBuilder::try_inline() with holder_known set to true which 
eventually lets profile_call() to be called with a non-NULL known_holder 
argument.

On the other hand, when calling a static method without a method handle, 
known_holder seems to be always NULL:
profile_call() is called directly at [2] with NULL or indirectly via 
try_inline() [3]. In the latter case, cha_monomorphic_target and 
exact_target are always NULL for static methods and therefore 
known_holder will also be always NULL in profile_call().

We could therefore just remove the assert which seems to be too strong 
(not handling this edge case). Another option would be to change the 
call to try_inline() in try_method_handle_inline() to only set 
holder_known to true if the target is not static. The known_holder is 
eventually only used in LIR_Assembler::emit_profile_call() [4] but only 
if op->should_profile_receiver_type() holds [5]. This is only true if 
the callee is not static [6]. The webrev uses the second approach.

What do you think?

Best regards,
Christian


[1] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/share/c1/c1_GraphBuilder.cpp#l4386
[2] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/share/c1/c1_GraphBuilder.cpp#l3571
[3] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/share/c1/c1_GraphBuilder.cpp#l2039
[4] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/cpu/x86/c1_LIRAssembler_x86.cpp#l3589
[5] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/cpu/x86/c1_LIRAssembler_x86.cpp#l3584
[6] 
http://hg.openjdk.java.net/jdk/jdk/file/dd0caf00b05c/src/hotspot/share/c1/c1_LIR.hpp#l1916