Zig crashes on LoongArch64

[xtexx]

Zig Version

0.14.0-dev.3187+d4c85079c

Steps to Reproduce and Observed Behavior

zig init then zig build, got 'zig build' terminated by signal SIGSEGV (Address boundary error)

On earlier versions, zig init build successfully but building the current master zig crashes (SIGBUS or SIGSEGV).
On latest versions, zig init-projects also could not be built.

Expected Behavior

It should build.

[mikdusan]

a reduction:

zig build-exe hello.zig

1. maybe a hint to the problem? release zig alternates between SIGSEGV and SIGBUS
2. debug zig thus far is always SIGSEGV

trace from debug zig

[4] compiler_rt
Thread 27 "zig" received signal SIGSEGV, Segmentation fault.
[Switching to LWP 4247]
0x000000000e50f81c in compiler_rt.memmove.copyForward () at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/compiler_rt/memmove.zig:130
warning: 130	/home/mike/project/zig-bootstrap/n2/out/host/lib/zig/compiler_rt/memmove.zig: No such file or directory
(gdb) bt
#0  0x000000000e50f81c in compiler_rt.memmove.copyForward () at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/compiler_rt/memmove.zig:130
#1  compiler_rt.memmove.copyMove () at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/compiler_rt/memmove.zig:111
#2  compiler_rt.memmove.memmoveFast (opt_dest=0x7fffd4dd3610 "", opt_src=0x7fffd4dd3618 "@", len=18446744073709551608)
    at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/compiler_rt/memmove.zig:65
#3  0x0000000005132cb0 in llvm::LoopInfoBase<llvm::BasicBlock, llvm::Loop>::removeBlock(llvm::BasicBlock*) ()
#4  0x000000000531bcc4 in llvm::MergeBlockIntoPredecessor(llvm::BasicBlock*, llvm::DomTreeUpdater*, llvm::LoopInfo*, llvm::MemorySSAUpdater*, llvm::MemoryDependenceResults*, bool, llvm::DominatorTree*) ()
#5  0x000000000564a254 in (anonymous namespace)::LoopRotate::processLoop(llvm::Loop*) ()
#6  0x00000000056478a0 in llvm::LoopRotation(llvm::Loop*, llvm::LoopInfo*, llvm::TargetTransformInfo const*, llvm::AssumptionCache*, llvm::DominatorTree*, llvm::ScalarEvolution*, llvm::MemorySSAUpdater*, llvm::SimplifyQuery const&, bool, unsigned int, bool, bool) ()
#7  0x0000000005646d38 in llvm::LoopRotatePass::run(llvm::Loop&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&) ()
#8  0x00000000050f601c in llvm::detail::PassModel<llvm::Loop, llvm::LoopRotatePass, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>::run(llvm::Loop&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&) ()
#9  0x0000000005c5d6a4 in std::__1::optional<llvm::PreservedAnalyses> llvm::PassManager<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>::runSinglePass<llvm::Loop, std::__1::unique_ptr<llvm::detail::PassConcept<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>, std::__1::default_delete<llvm::detail::PassConcept<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&> > > >(llvm::Loop&, std::__1::unique_ptr<llvm::detail::PassConcept<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>, std::__1::default_delete<llvm::detail::PassConcept<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&> > >&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&, llvm::PassInstrumentation&) ()
#10 0x0000000005c5d400 in llvm::PassManager<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>::runWithoutLoopNestPasses(llvm::Loop&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&) ()
#11 0x0000000005c5cd8c in llvm::PassManager<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>::run(llvm::Loop&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&) ()
#12 0x00000000050f1cdc in llvm::detail::PassModel<llvm::Loop, llvm::PassManager<llvm::Loop, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&>::run(llvm::Loop&, llvm::AnalysisManager<llvm::Loop, llvm::LoopStandardAnalysisResults&>&, llvm::LoopStandardAnalysisResults&, llvm::LPMUpdater&) ()
#13 0x0000000005c5e0b4 in llvm::FunctionToLoopPassAdaptor::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) ()
#14 0x00000000050f7abc in llvm::detail::PassModel<llvm::Function, llvm::FunctionToLoopPassAdaptor, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&)
    ()
#15 0x0000000005030bd4 in llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) ()
#16 0x00000000050fe75c in llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) ()
#17 0x00000000056d7b34 in llvm::CGSCCToFunctionPassAdaptor::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#18 0x00000000050feadc in llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::CGSCCToFunctionPassAdaptor, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#19 0x00000000056d513c in llvm::PassManager<llvm::LazyCallGraph::SCC, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#20 0x000000000511237c in llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::PassManager<llvm::LazyCallGraph::SCC, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#21 0x00000000056d6b48 in llvm::DevirtSCCRepeatedPass::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#22 0x000000000568df1c in llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::DevirtSCCRepeatedPass, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) ()
#23 0x00000000056d6150 in llvm::ModuleToPostOrderCGSCCPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
#24 0x000000000510297c in llvm::detail::PassModel<llvm::Module, llvm::ModuleToPostOrderCGSCCPassAdaptor, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&)
    ()
#25 0x000000000502f854 in llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
#26 0x0000000005689364 in llvm::ModuleInlinerWrapperPass::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
#27 0x00000000050ff03c in llvm::detail::PassModel<llvm::Module, llvm::ModuleInlinerWrapperPass, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
#28 0x000000000502f854 in llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
--Type <RET> for more, q to quit, c to continue without paging--
#29 0x0000000004d9297c in ZigLLVMTargetMachineEmitToFile (targ_machine_ref=0x7fffd64f0020, module_ref=0x7fffd795cfb0, error_message=0x7fffdee9ec60, options=0x7fffdee9f090) at /home/mike/project/zig-bootstrap/n2/zig/src/zig_llvm.cpp:379
#30 0x000000000b1a7c44 in codegen.llvm.Object.emit (o=0x7fffdde4c250, options=...) at /home/mike/project/zig-bootstrap/n2/zig/src/codegen/llvm.zig:1384
#31 0x000000000b1a09c0 in Compilation.emitLlvmObject (comp=0x7fffdde96f80, arena=..., default_artifact_directory=..., bin_emit_loc=..., llvm_object=0x7fffdde4c250, prog_node=...) at Compilation.zig:2735
#32 0x000000000b8cf7f0 in link.File.emitLlvmObject (base=..., arena=..., llvm_object=0x7fffdde4c250, prog_node=...) at link.zig:1335
#33 0x000000000b62891c in link.Elf.flushModule (self=0x7fffdde9aac0, arena=..., tid=main, prog_node=...) at /home/mike/project/zig-bootstrap/n2/zig/src/link/Elf.zig:819
#34 0x000000000b5f85bc in link.File.flushModule (base=0x7fffdde9ae30, arena=..., tid=main, prog_node=...) at link.zig:842
#35 0x000000000b5f5970 in link.File.linkAsArchiveInner (base=0x7fffdde9ae30, arena=..., tid=main, prog_node=...) at link.zig:1095
#36 0x000000000b3c95c4 in link.File.linkAsArchive (base=0x7fffdde9ae30, arena=..., tid=main, prog_node=...) at link.zig:1077
#37 0x000000000b1a865c in link.File.flush (base=0x7fffdde9ae30, arena=..., tid=main, prog_node=...) at link.zig:826
#38 0x000000000b1a80b8 in Compilation.flush (comp=0x7fffdde96f80, arena=..., default_artifact_directory=..., tid=main, prog_node=...) at Compilation.zig:2438
#39 0x000000000b1ae16c in Compilation.update (comp=0x7fffdde96f80, main_progress_node=...) at Compilation.zig:2375
#40 0x000000000c161980 in Compilation.updateSubCompilation (parent_comp=0x7ffff7f791c0, sub_comp=0x7fffdde96f80, misc_task=compiler_rt, prog_node=...) at Compilation.zig:6448
#41 0x000000000c1644ac in Compilation.buildOutputFromZig (comp=0x7ffff7f791c0, src_basename=..., output_mode=Lib, allow_lto=false, out=0x7ffff7f797f8, misc_task_tag=compiler_rt, prog_node=...) at Compilation.zig:6591
#42 0x000000000bcc3058 in Compilation.buildRt (comp=0x7ffff7f791c0, root_source_name=..., misc_task=compiler_rt, output_mode=Lib, allow_lto=false, out=0x7ffff7f797f8, prog_node=...) at Compilation.zig:4681
#43 0x000000000b83c284 in Thread.WaitGroup.spawnManager__anon_183554.Manager.run (wg_inner=0x7ffff7f79378, args_inner=...) at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/std/Thread/WaitGroup.zig:66
#44 0x000000000c161850 in Thread.callFn__anon_353682 (args=...) at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/std/Thread.zig:488
#45 0x000000000bcc2f40 in Thread.PosixThreadImpl.spawn__anon_280580.Instance.entryFn (raw_arg=0x7ffff7fb4860) at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/std/Thread.zig:757
#46 0x000000000e4e4330 in start (p=0x7fffdeea3680) at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/libc/musl/src/thread/pthread_create.c:207
#47 0x000000000e4e29e0 in __clone () at /home/mike/project/zig-bootstrap/n2/out/host/lib/zig/libc/musl/src/thread/loongarch64/clone.s:28

---

I used the following steps to get zig-bootstrap to generate a loongarch64 debug binary:

1. clone zig-bootstrap master
2. cd TOP
3. rm -fr zig
4. git clone https://github.com/ziglang/zig.git
5. apply the following quick'n'dirty patch:

diff --git a/build b/build
index fb259b0ff..c9f67f491 100755
--- a/build
+++ b/build
@@ -5,9 +5,10 @@ set -eu

 TARGET="$1" # Example: riscv64-linux-gnu
 MCPU="$2" # Examples: `baseline`, `native`, `generic+v7a`, or `arm1176jzf_s`
+MCMODEL_FLAGS="-mcmodel=medium"

 ROOTDIR="$(pwd)"
-ZIG_VERSION="0.14.0-dev.2257+e6d2e1641"
+ZIG_VERSION="0.14.0-dev.3205+6dc1a4db7"

 TARGET_OS_AND_ABI=${TARGET#*-} # Example: linux-gnu

@@ -98,6 +99,7 @@ $ZIG build-lib \
   --name zstd \
   -target $TARGET \
   -mcpu=$MCPU \
+  $MCMODEL_FLAGS \
   -fstrip -OReleaseFast \
   -lc \
   "$ROOTDIR/zstd/lib/decompress/zstd_ddict.c" \
@@ -197,8 +199,8 @@ $ZIG build \
   --search-prefix "$ROOTDIR/out/$TARGET-$MCPU" \
   -Dflat \
   -Dstatic-llvm \
-  -Doptimize=ReleaseFast \
-  -Dstrip \
+  -Doptimize=Debug \
+  -Dstrip=false \
   -Dtarget="$TARGET" \
   -Dcpu="$MCPU" \
   -Dversion-string="$ZIG_VERSION"

6. don't forget to update ZIG_VERSION in build script (hint: git --work-tree=zig describe)
7. ./build loongarch64-linux-musl baseline

[mikdusan]

$ git bisect bad
f278038923c33ddf710f0328a07ce18613a94130 is the first bad commit
commit f278038923c33ddf710f0328a07ce18613a94130 (HEAD)
Author:     David Rubin <daviru007@icloud.com>
AuthorDate: Sat Nov 30 16:08:26 2024 -0800
Commit:     Andrew Kelley <andrew@ziglang.org>
CommitDate: Fri Jan 17 12:34:15 2025 -0800

    replace `compiler_rt` memcpy with a better version

 lib/compiler_rt.zig         |   1 -
 lib/compiler_rt/memcpy.zig  | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 lib/compiler_rt/memmove.zig |  25 ----------------
 3 files changed, 130 insertions(+), 39 deletions(-)
 delete mode 100644 lib/compiler_rt/memmove.zig

[xtexx]

For record, @mikdusan reported on zulip that applying #22606 resolves this for Debug zig but release zig still crashes.

However, both Debug and ReleaseSafe zig worked for me. I have successfully compiled Debug zig from the ReleaseSafe LoongArch64 zig.

[xtexx]

#22606 crashes in ReleaseFast. Debug, ReleaseSmall, ReleaseSafe not crash.

ReleaseFast crashes on another place:

#0  fifo.LinearFifo(InternPool.FileIndex,.{ .Dynamic = {} }).readItem (self=0x7fffe75675f8) at /buildroots/xtex/zig-bootstrap/zig/lib/std/fifo.zig:210
#1  Compilation.performAllTheWorkInner (comp=0x7fffe75671e0, main_progress_node=...) at Compilation.zig:3786
#2  0x000000000a5bc2f8 in Compilation.performAllTheWork (comp=0x7fffe75671e0) at Compilation.zig:3645
#3  Compilation.update (comp=0x7fffe75671e0, main_progress_node=...) at Compilation.zig:2259
#4  0x000000000a5e480c in main.updateModule (comp=0x7fffe75671e0, color=<optimized out>, prog_node=<error reading variable: Cannot access memory at address 0x81>) at main.zig:4500
#5  0x000000000a6823f0 in main.cmdBuild (arena=...) at main.zig:5322
#6  0x000000000a554a60 in main.mainArgs (arena=...) at main.zig:293
#7  main.main () at main.zig:212
#8  start.callMain () at /buildroots/xtex/zig-bootstrap/zig/lib/std/start.zig:656
#9  start.callMainWithArgs () at /buildroots/xtex/zig-bootstrap/zig/lib/std/start.zig:616
#10 start.main (c_argc=<optimized out>, c_argv=<optimized out>, c_envp=<optimized out>) at /buildroots/xtex/zig-bootstrap/zig/lib/std/start.zig:631

[xtexx]

There seems to be some race conditions (or miscomp?). By repeating starting Zig, it sometimes worked well!

[alexrp]

All analysis on this so far indicates that we're hitting multiple LLVM bugs. The plan is to ship 0.14.0 with this regression and hope that the situation has improved in LLVM 20.