RFR(S): 8243670: Unexpected test result caused by C2 MergeMemNode::Ideal

[Yangfei (Felix)]

Hi,

> -----Original Message-----
> From: Roland Westrelin [mailto:rwestrel at redhat.com]
> Sent: Tuesday, June 23, 2020 4:58 PM
> To: Yangfei (Felix) <felix.yang at huawei.com>; Tobias Hartmann
> <tobias.hartmann at oracle.com>; hotspot-compiler-dev at openjdk.java.net
> Cc: guoge (A) <guoge1 at huawei.com>; zhouyong (V)
> <zhouyong44 at huawei.com>
> Subject: RE: RFR(S): 8243670: Unexpected test result caused by C2
> MergeMemNode::Ideal
> 
> 
> > # A fatal error has been detected by the Java Runtime Environment:
> > #
> > #  Internal Error
> > (/home/yangfei/openjdk-jdk/src/hotspot/share/opto/phaseX.cpp:1135),
> > pid=10598, tid=10613 #  assert(false) failed: infinite loop in
> > PhaseIterGVN::optimize
> 
> For known instances, MemNode::optimize_memory_chain() clones the
> bottom phi into a new phi that your patch then clones to create a bottom phi.
> 
> diff --git a/src/hotspot/share/opto/cfgnode.cpp
> b/src/hotspot/share/opto/cfgnode.cpp
> --- a/src/hotspot/share/opto/cfgnode.cpp
> +++ b/src/hotspot/share/opto/cfgnode.cpp
> @@ -1337,7 +1337,7 @@
> 
>    // Looking for phis with identical inputs.  If we find one that has
>    // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
> -  if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
> TypePtr::BOTTOM) {
> +  if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
> + TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
>      uint phi_len = req();
>      Node* phi_reg = region();
>      for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
> 
> fixes it.

Thanks, Roland.
I updated accordingly, new webrev: http://cr.openjdk.java.net/~fyang/8243670/webrev.02 
Tier1-3 tested with fastdebug builds both on x86_64-linux-gnu and aarch64-linux-gnu. 
Newly added test fail without the fix and pass otherwise.
Also committed to the submit repo and test results looks good: 

Job: mach5-one-fyang-JDK-8243670-2-20200623-1609-12020284
BuildId: 2020-06-23-1608238.felix.yang.source
No failed tests
Tasks Summary
•	EXECUTED_WITH_FAILURE: 0
•	KILLED: 0
•	HARNESS_ERROR: 0
•	PASSED: 103
•	UNABLE_TO_RUN: 0
•	NOTHING_TO_RUN: 0
•	FAILED: 0
•	NA: 0

Shall I do the push? 

Felix