Bug ID: JDK-8229483 Sinking load out of loop may trigger: assert(found_sfpt) failed: no node in loop that's not input to safepoint

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JDK 11	JDK 13	JDK 14
11.0.6Fixed	13.0.4Fixed	14 b16Fixed

(synopsis is provisional, please change as you see fit)

Found with fuzzing, the bundle is attached. Reproduces with Shenandoah, not with G1.

$ jdk-jdk/build/linux-x86_64-server-fastdebug/images/jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC Test

# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc:  SuppressErrorAt=/loopnode.cpp:992
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/home/shade/trunks/jdk-jdk/src/hotspot/share/opto/loopnode.cpp:992), pid=12041, tid=12050
#  assert(found_sfpt) failed: no node in loop that's not input to safepoint
#
# JRE version: OpenJDK Runtime Environment (14.0) (fastdebug build 14-internal+0-adhoc.shade.jdk-jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 14-internal+0-adhoc.shade.jdk-jdk, mixed mode, sharing, tiered, compressed oops, shenandoah gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0x11f2cb8]  LoopNode::verify_strip_mined(int) const+0x5f8

13u Fix Request Backporting this patch fixes a c2 crash. Patch applies cleanly to 13u. tier1 tests pass with the patch.
27-05-2020
I believe this does not affect 8-shenandoah, because LSM is not there. Neither new test nor the fuzzer test case fails in sh/jdk8. Dropping relevant affected version.
30-10-2019
11u Fix Request Backporting this patch fixes a c2 crash. Patch applies cleanly to 11u. New test fails without the product patch, and passes with it. tier1 tests pass with the patch.
02-10-2019
URL: https://hg.openjdk.java.net/jdk/jdk/rev/88fce7eea1f6 User: roland Date: 2019-09-25 07:35:36 +0000
25-09-2019
Test case that reproduces without Shenandoah attached. Run with: java -XX:-TieredCompilation -XX:-BackgroundCompilation -XX:-UseOnStackReplacement -XX:+PrintCompilation -XX:PrintIdealGraphFile=graph.xml -XX:PrintIdealGraphLevel=2 -XX:CompileOnly=AntiDependentLoadInOuterStripMinedLoop::test -XX:LoopMaxUnroll=0 AntiDependentLoadInOuterStripMinedLoop Prototype fix: diff -r 2227a0cfd6b3 -r 5f4af4e56160 src/hotspot/share/opto/loopopts.cpp --- a/src/hotspot/share/opto/loopopts.cpp Thu Aug 22 13:47:14 2019 +0200 +++ b/src/hotspot/share/opto/loopopts.cpp Thu Aug 22 16:31:20 2019 +0200 @@ -1418,6 +1418,11 @@ // Such nodes should only have ProjNodes as outs, e.g. IfNode // should only have IfTrueNode and IfFalseNode (4985384). x_ctrl = find_non_split_ctrl(x_ctrl); + + IdealLoopTree* x_loop = get_loop(x_ctrl); + if (x_loop->_head->is_OuterStripMinedLoop() && is_dominator(n_ctrl, x_loop->_head)) { + x_ctrl = x_loop->_head->in(LoopNode::EntryControl); + } assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone"); x->set_req(0, x_ctrl);
23-08-2019
The tests does pass with -XX:-SplitIfBlocks. But it reproduces only with Shenandoah, not G1, not Serial, not Parallel, not ZGC. So, this might still be Shenandoah-specific. I linked the bugs, though.
13-08-2019
both Shenandoah and G1 set LoopStripMiningIter to 1000, so both of them should do loop strip-mining.
13-08-2019
Can you pass it with -XX:-SplitIfBlocks? If you can, probably it's same as JDK-8229450.
13-08-2019

Duplicate :	JDK-8230798 - [lworld] C2 compilation fails with ShouldNotReachHere in verify_strip_mined_scheduling
Relates :	JDK-8260420 - C2 compilation fails with assert(found_sfpt) failed: no node in loop that's not input to safepoint
Relates :	JDK-8252372 - Check if cloning is required to move loads out of loops in PhaseIdealLoop::split_if_with_blocks_post()
Relates :	JDK-8264958 - C2 compilation fails with assert "n is later than its clone"
Relates :	JDK-8229450 - C2 compilation fails with assert(found_sfpt) failed: no node in loop that's not input to safepoint