RFR(S): 8231988: Unexpected test result caused by C2 IdealLoopTree::do_remove_empty_loop
Yangfei (Felix)
felix.yang at huawei.com
Tue Oct 8 08:14:24 UTC 2019
Hi,
Could I have a review for this trivial C2 bugfix please?
Bug: https://bugs.openjdk.java.net/browse/JDK-8231988
This bug is always reproducible with 8u, 11u, 13 and latest 14.
After some investigation, we found that the cmp node in one empty loop was deleted by IdealLoopTree::do_remove_empty_loop, but it still has another user outside the empty loop.
C2 call stack:
#0 IdealLoopTree::do_remove_empty_loop (this=0x96b060, phase=0xffff5c3815c0) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopTransform.cpp:3131
#1 0x0000ffffb7077f70 in IdealLoopTree::iteration_split_impl (this=0x96b060, phase=0xffff5c3815c0, old_new=...)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopTransform.cpp:3186
#2 0x0000ffffb7078590 in IdealLoopTree::iteration_split (this=0x96b060, phase=0xffff5c3815c0, old_new=...)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopTransform.cpp:3336
#3 0x0000ffffb70784a8 in IdealLoopTree::iteration_split (this=0x96b130, phase=0xffff5c3815c0, old_new=...)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopTransform.cpp:3320
#4 0x0000ffffb708a2c8 in PhaseIdealLoop::build_and_optimize (this=0xffff5c3815c0, mode=LoopOptsDefault)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.cpp:3088
#5 0x0000ffffb6a46e58 in PhaseIdealLoop::PhaseIdealLoop (this=0xffff5c3815c0, igvn=..., mode=LoopOptsDefault)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.hpp:945
#6 0x0000ffffb6a46f18 in PhaseIdealLoop::optimize (igvn=..., mode=LoopOptsDefault) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.hpp:1020
#7 0x0000ffffb6a3abc8 in Compile::Optimize (this=0xffff5c3847a8) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:2328
#8 0x0000ffffb6a3458c in Compile::Compile (this=0xffff5c3847a8, ci_env=0xffff5c385558, compiler=0xffff581e2110, target=0x928e20, osr_bci=-1,
subsume_loads=true, do_escape_analysis=true, eliminate_boxing=true, directive=0xffff581b1e70)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:874
#9 0x0000ffffb690a508 in C2Compiler::compile_method (this=0xffff581e2110, env=0xffff5c385558, target=0x928e20, entry_bci=-1, directive=0xffff581b1e70)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/c2compiler.cpp:110
#10 0x0000ffffb6a506c8 in CompileBroker::invoke_compiler_on_method (task=0xffff5824df80)
at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:2115
#11 0x0000ffffb6a4f554 in CompileBroker::compiler_thread_loop () at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:1800
#12 0x0000ffffb747be0c in compiler_thread_entry (thread=0xffff581e2800, __the_thread__=0xffff581e2800)
at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:3401
#13 0x0000ffffb7477208 in JavaThread::thread_main_inner (this=0xffff581e2800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1917
#14 0x0000ffffb747708c in JavaThread::run (this=0xffff581e2800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1900
#15 0x0000ffffb7473270 in Thread::call_run (this=0xffff581e2800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:398
#16 0x0000ffffb71e1574 in thread_native_entry (thread=0xffff581e2800) at /home/yangfei/openjdk-jdk/src/hotspot/os/linux/os_linux.cpp:792
#17 0x0000ffffb7f3edc4 in start_thread () from /lib64/libpthread.so.0
#18 0x0000ffffb7e73fd0 in thread_start () from /lib64/libc.so.6
The other use of the cmp node was created by:
#0 PhaseStringOpts::getChars (this=0xffff5c383630, kit=..., arg=0xafaf88, dst_array=0xffff58021cd8, bt=T_BYTE, end=0xaef210, final_merge=0xffff58022b18,
final_mem=0xffff58022bb0, merge_index=0) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/stringopts.cpp:1251
#1 0x0000ffffb73d72b4 in PhaseStringOpts::int_getChars (this=0xffff5c383630, kit=..., arg=0xafaf88, dst_array=0xffff58021cd8, dst_coder=0xb2d080,
start=0xffff580226f8, size=0xaebdf0) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/stringopts.cpp:1396
#2 0x0000ffffb73d93bc in PhaseStringOpts::replace_string_concat (this=0xffff5c383630, sc=0xb1bf10)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/stringopts.cpp:1932
#3 0x0000ffffb73d3cfc in PhaseStringOpts::PhaseStringOpts (this=0xffff5c383630, gvn=0xffff5c383aa8)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/stringopts.cpp:667
#4 0x0000ffffb6a39798 in Compile::inline_string_calls (this=0xffff5c384528, parse_time=true)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:2026
#5 0x0000ffffb6a343d4 in Compile::Compile (this=0xffff5c384528, ci_env=0xffff5c3852d8, compiler=0xffff58002f70, target=0xb03050, osr_bci=-1,
subsume_loads=true, do_escape_analysis=true, eliminate_boxing=true, directive=0xa85fb0)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:834
#6 0x0000ffffb690a508 in C2Compiler::compile_method (this=0xffff58002f70, env=0xffff5c3852d8, target=0xb03050, entry_bci=-1, directive=0xa85fb0)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/c2compiler.cpp:110
#7 0x0000ffffb6a506c8 in CompileBroker::invoke_compiler_on_method (task=0xffff58085340)
at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:2115
#8 0x0000ffffb6a4f554 in CompileBroker::compiler_thread_loop () at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:1800
#9 0x0000ffffb747be0c in compiler_thread_entry (thread=0xffff58010800, __the_thread__=0xffff58010800)
at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:3401
#10 0x0000ffffb7477208 in JavaThread::thread_main_inner (this=0xffff58010800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1917
#11 0x0000ffffb747708c in JavaThread::run (this=0xffff58010800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1900
#12 0x0000ffffb7473270 in Thread::call_run (this=0xffff58010800) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:398
#13 0x0000ffffb71e1574 in thread_native_entry (thread=0xffff58010800) at /home/yangfei/openjdk-jdk/src/hotspot/os/linux/os_linux.cpp:792
#14 0x0000ffffb7f3edc4 in start_thread () from /lib64/libpthread.so.0
#15 0x0000ffffb7e73fd0 in thread_start () from /lib64/libc.so.6
Cmp node was deleted by:
#0 PhaseIterGVN::optimize (this=0xffff5c381f28) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/phaseX.cpp:1162
#1 0x0000ffffb708a630 in PhaseIdealLoop::build_and_optimize (this=0xffff5c3812c0, mode=LoopOptsDefault)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.cpp:3163
#2 0x0000ffffb6a46e58 in PhaseIdealLoop::PhaseIdealLoop (this=0xffff5c3812c0, igvn=..., mode=LoopOptsDefault)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.hpp:945
#3 0x0000ffffb6a46f18 in PhaseIdealLoop::optimize (igvn=..., mode=LoopOptsDefault) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/loopnode.hpp:1020
#4 0x0000ffffb6a3abc8 in Compile::Optimize (this=0xffff5c3844a8) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:2328
#5 0x0000ffffb6a3458c in Compile::Compile (this=0xffff5c3844a8, ci_env=0xffff5c385258, compiler=0xaaf7a0, target=0xb19630, osr_bci=-1, subsume_loads=true,
do_escape_analysis=true, eliminate_boxing=true, directive=0xa85fb0) at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/compile.cpp:874
#6 0x0000ffffb690a508 in C2Compiler::compile_method (this=0xaaf7a0, env=0xffff5c385258, target=0xb19630, entry_bci=-1, directive=0xa85fb0)
at /home/yangfei/openjdk-jdk/src/hotspot/share/opto/c2compiler.cpp:110
#7 0x0000ffffb6a506c8 in CompileBroker::invoke_compiler_on_method (task=0xffff58067330)
at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:2115
#8 0x0000ffffb6a4f554 in CompileBroker::compiler_thread_loop () at /home/yangfei/openjdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:1800
#9 0x0000ffffb747be0c in compiler_thread_entry (thread=0xabd000, __the_thread__=0xabd000)
at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:3401
#10 0x0000ffffb7477208 in JavaThread::thread_main_inner (this=0xabd000) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1917
#11 0x0000ffffb747708c in JavaThread::run (this=0xabd000) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:1900
#12 0x0000ffffb7473270 in Thread::call_run (this=0xabd000) at /home/yangfei/openjdk-jdk/src/hotspot/share/runtime/thread.cpp:398
#13 0x0000ffffb71e1574 in thread_native_entry (thread=0xabd000) at /home/yangfei/openjdk-jdk/src/hotspot/os/linux/os_linux.cpp:792
#14 0x0000ffffb7f3edc4 in start_thread () from /lib64/libpthread.so.0
#15 0x0000ffffb7e73fd0 in thread_start () from /lib64/libc.so.6
Proposed patch duplicate the cmp node if it has other users:
diff -r 5b5de2618756 src/hotspot/share/opto/loopTransform.cpp
--- a/src/hotspot/share/opto/loopTransform.cpp Mon Oct 07 17:13:59 2019 -0700
+++ b/src/hotspot/share/opto/loopTransform.cpp Wed Oct 09 15:39:42 2019 +0800
@@ -3129,6 +3129,13 @@
// We also need to replace the original limit to collapse loop exit.
Node* cmp = cl->loopexit()->cmp_node();
assert(cl->limit() == cmp->in(2), "sanity");
+ // Duplicate cmp node if it has other users
+ if (cmp->outcnt() > 1) {
+ cmp = cmp->clone();
+ cmp = phase->_igvn.register_new_node_with_optimizer(cmp);
+ BoolNode *bol = cl->loopexit()->in(CountedLoopEndNode::TestValue)->as_Bool();
+ phase->_igvn.replace_input_of(bol, 1, cmp); // put bol on worklist
+ }
phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
}
Patch is currently under testing.
Thanks,
Felix
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