From @MasterDuke17

gdb --args /home/dan/Source/perl6/install/bin/moar
--libpath="/home/dan/Source/perl6/install/share/nqp/lib"
--libpath="/home/dan/Source/perl6/install/share/nqp/lib" perl6.moarvm
--nqp-lib=blib --setting=NULL --ll-exception --optimize=3 --target=mbc
--stagestats --output=CORE.setting.moarvm --profile-stage=parse
--profile-filename=compile_20170625.sql gen/moar/CORE.setting

(gdb) bt
#​0 MVM_repr_at_pos_i (tc=tc@​entry=0x555555758800, obj=obj@​entry=0x0,
idx=0) at src/6model/reprconv.c​:84
#​1 0x00007ffff77cab1d in MVM_nfa_run_alt (tc=0x555555758800,
nfa=<optimized out>, target=<optimized out>, offset=322,
bstack=0x7ffff6674478, cstack=<optimized out>, labels=0x0) at
src/6model/reprs/NFA.c​:764
#​2 0x00007ffff7776e93 in MVM_interp_run (tc=tc@​entry=0x555555758800,
initial_invoke=0x0, invoke_data=0x0) at src/core/interp.c​:1692
#​3 0x00007ffff783a5c1 in MVM_vm_run_file (instance=0x555555758010,
filename=0x7fffffffe152 "perl6.moarvm") at src/moar.c​:318
#​4 0x0000555555555405 in main (argc=14, argv=0x7fffffffdce8) at
src/main.c​:246

(gdb) call MVM_dump_backtrace(tc)
  at <unknown>​:1
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:run_alt)
from gen/moar/stage2/QRegex.nqp​:1756
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:!alt)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:_ws)
from src/Perl6/Grammar.nqp​:616 (blib/Perl6/Grammar.moarvm​:ws)
from src/Perl6/Grammar.nqp​:1215 (blib/Perl6/Grammar.moarvm​:statementlist)
from src/Perl6/Grammar.nqp​:1394 (blib/Perl6/Grammar.moarvm​:blockoid)
from src/Perl6/Grammar.nqp​:2478 (blib/Perl6/Grammar.moarvm​:package_def)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:package_declarator​:sym<class>)
from gen/moar/stage2/QRegex.nqp​:1720
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:!protoregex)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:package_declarator)
from src/Perl6/Grammar.nqp​:2587 (blib/Perl6/Grammar.moarvm​:scoped)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:scope_declarator​:sym<my>)
from gen/moar/stage2/QRegex.nqp​:1720
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:!protoregex)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:scope_declarator)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:term​:sym<scope_declarator>)
from gen/moar/stage2/QRegex.nqp​:1720
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:!protoregex)
from <unknown>​:1 (blib/Perl6/Grammar.moarvm​:term)
from src/Perl6/Grammar.nqp​:3924 (blib/Perl6/Grammar.moarvm​:termish)
from gen/moar/stage2/NQPHLL.nqp​:936
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:EXPR)
from src/Perl6/Grammar.nqp​:3964 (blib/Perl6/Grammar.moarvm​:EXPR)
from src/Perl6/Grammar.nqp​:1291 (blib/Perl6/Grammar.moarvm​:statement)
from src/Perl6/Grammar.nqp​:1223 (blib/Perl6/Grammar.moarvm​:statementlist)
from gen/moar/stage2/NQPHLL.nqp​:1166
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:LANG)
from src/Perl6/Grammar.nqp​:1665 (blib/Perl6/Grammar.moarvm​:FOREIGN_LANG)
from src/Perl6/Grammar.nqp​:1187 (blib/Perl6/Grammar.moarvm​:comp_unit)
from src/Perl6/Grammar.nqp​:496 (blib/Perl6/Grammar.moarvm​:TOP)
from gen/moar/stage2/QRegex.nqp​:2322
(/home/dan/Source/perl6/install/share/nqp/lib/QRegex.moarvm​:parse)
from gen/moar/stage2/NQPHLL.nqp​:1910
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:parse)
from gen/moar/stage2/NQPHLL.nqp​:1851
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:run)
from gen/moar/stage2/NQPHLL.nqp​:64
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:run_profiled)
from gen/moar/stage2/NQPHLL.nqp​:1861
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:)
from gen/moar/stage2/NQPHLL.nqp​:1839
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:compile)
from gen/moar/stage2/NQPHLL.nqp​:1571
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:eval)
from gen/moar/stage2/NQPHLL.nqp​:1806
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:evalfiles)
from gen/moar/stage2/NQPHLL.nqp​:1703
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:command_eval)
from src/Perl6/Compiler.nqp​:42 (blib/Perl6/Compiler.moarvm​:command_eval)
from gen/moar/stage2/NQPHLL.nqp​:1677
(/home/dan/Source/perl6/install/share/nqp/lib/NQPHLL.moarvm​:command_line)
from gen/moar/main.nqp​:47 (perl6.moarvm​:MAIN)
from gen/moar/main.nqp​:38 (perl6.moarvm​:<mainline>)
from <unknown>​:1 (perl6.moarvm​:<main>)
from <unknown>​:1 (perl6.moarvm​:<entry>)

From @timo

this was caused by instructions coming back from the dead, haunting usage counts by mysteriously dropping them by 1 or more, and then both the dead instruction and the lawful citizens of other blocks of code being executed by the local authorities.

fixed with MoarVM/MoarVM@3d3d0d05df

The RT System itself - Status changed from 'new' to 'open'

@timo - Status changed from 'open' to 'resolved'