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Bug 1797127

Summary: Rust 1.41 fails to build on Fedora 30 i686
Product: [Fedora] Fedora Reporter: Josh Stone <jistone>
Component: llvmAssignee: Tom Stellard <tstellar>
Status: CLOSED ERRATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 30CC: dmalcolm, igor.raits, jakub, jistone, rust-sig,, sean, sguelton, siddharth.kde, TicoTimo, tstellar
Target Milestone: ---   
Target Release: ---   
Hardware: i686   
OS: Unspecified   
Fixed In Version: llvm-8.0.0-7.fc30 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2020-02-27 22:05:42 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Description Flags
llvm-ir for a 64-bit atomic_load_unordered none

Description Josh Stone 2020-02-01 00:21:28 UTC
Description of problem:
In rust-1.41.0-1.fc30:

The i686 build triggered a segmentation fault while compiling compiler_builtins in stage0 (using the prior version of the toolchain). All other arches completed the build without trouble.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Try to build rust-1.41.0-1.fc30

Actual results:

Building stage0 std artifacts (i686-unknown-linux-gnu -> i686-unknown-linux-gnu)
   Compiling compiler_builtins v0.1.22
   Compiling core v0.0.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/libcore)
   Compiling cc v1.0.47
   Compiling libc v0.2.64
   Compiling autocfg v0.1.6
   Compiling std v0.0.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/libstd)
   Compiling hashbrown v0.6.2
   Compiling unwind v0.0.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/libunwind)
   Compiling backtrace-sys v0.1.32
   Compiling rustc-std-workspace-core v1.99.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/tools/rustc-std-workspace-core)
   Compiling cfg-if v0.1.8
   Compiling alloc v0.0.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/liballoc)
   Compiling rustc-demangle v0.1.16
   Compiling panic_abort v0.0.0 (/builddir/build/BUILD/rustc-1.41.0-src/src/libpanic_abort)
error: could not compile `compiler_builtins`.

Caused by:
  process didn't exit successfully: `/builddir/build/BUILD/rustc-1.41.0-src/build/bootstrap/debug/rustc --crate-name compiler_builtins /builddir/build/BUILD/rustc-1.41.0-src/vendor/compiler_builtins/src/ --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C codegen-units=1 -C debuginfo=2 -C debug-assertions=off -C overflow-checks=on --cfg 'feature="compiler-builtins"' --cfg 'feature="core"' --cfg 'feature="default"' --cfg 'feature="rustc-dep-of-std"' -C metadata=302301c59b8bd4fb -C extra-filename=-302301c59b8bd4fb --out-dir /builddir/build/BUILD/rustc-1.41.0-src/build/i686-unknown-linux-gnu/stage0-std/i686-unknown-linux-gnu/debug/deps --target i686-unknown-linux-gnu -L dependency=/builddir/build/BUILD/rustc-1.41.0-src/build/i686-unknown-linux-gnu/stage0-std/i686-unknown-linux-gnu/debug/deps -L dependency=/builddir/build/BUILD/rustc-1.41.0-src/build/i686-unknown-linux-gnu/stage0-std/debug/deps --extern core=/builddir/build/BUILD/rustc-1.41.0-src/build/i686-unknown-linux-gnu/stage0-std/i686-unknown-linux-gnu/debug/deps/librustc_std_workspace_core-148617687675f4a5.rmeta --cap-lints allow -Clink-arg=-Wl,-z,relro,-z,now --cfg=bootstrap -Zexternal-macro-backtrace -Wrust_2018_idioms -Wunused_lifetimes -Dwarnings -Cprefer-dynamic -Zbinary-dep-depinfo --cfg 'feature="unstable"'` (signal: 11, SIGSEGV: invalid memory reference)
warning: build failed, waiting for other jobs to finish...
error: build failed

Expected results:
A normal build.

Additional info:
Preliminary debugging shows the SIGSEGV is raised within LLVM, but the backtrace looks corrupt.

Thread 5 "rustc" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xe97ffb40 (LWP 1549)]
expandAtomicCmpXchg () at ../lib/CodeGen/AtomicExpandPass.cpp:1246
1246        Builder.SetInsertPoint(ExitBB, ++ExitBB->begin());
(gdb) bt
#0  expandAtomicCmpXchg () at ../lib/CodeGen/AtomicExpandPass.cpp:1246
#1  0xf06a802b in ?? () from /lib/
#2  0x535f6c61 in ?? ()
#3  0x74666968 in ?? ()
#4  0x43006465 in ?? ()
#5  0x6156706d in ?? ()

I will try to get the llvm-ir to reproduce this on its own.

Comment 1 Josh Stone 2020-02-01 01:36:39 UTC
Created attachment 1656893 [details]
llvm-ir for a 64-bit atomic_load_unordered

#![crate_type = "lib"]

pub unsafe fn unordered_load(src: *const u64) {

Comment 2 Josh Stone 2020-02-01 01:42:48 UTC
The attachment is the full llvm-ir for the given Rust code, basically just a 64-bit unordered load alone:

  %1 = load atomic i64, i64* %src unordered, align 8

Compiled with llc in llvm-8.0.0-6.fc30.i686:

Stack dump:
0.      Program arguments: llc load.ll
1.      Running pass 'Function Pass Manager' on module 'load.ll'.
2.      Running pass 'Expand Atomic instructions' on function '@unordered_load'
#0 0xfffffffff3b29227 llvm::sys::PrintStackTrace(llvm::raw_ostream&) ../lib/Support/Unix/
#1 0xfffffffff3b29301 ../lib/Support/Unix/
#2 0xfffffffff3b27011 llvm::sys::RunSignalHandlers() ../lib/Support/Signals.cpp:69:20
#3 0xfffffffff3b27195 ../lib/Support/Unix/
#4 0xfffffffff7f9db70 (
#5 0xfffffffff393b6d0 ../include/llvm/IR/TrackingMDRef.h:34:48
#6 0xfffffffff393b6d0 ../include/llvm/IR/TrackingMDRef.h:115:62
#7 0xfffffffff393b6d0 ../include/llvm/IR/DebugLoc.h:34:9
#8 0xfffffffff393b6d0 ../include/llvm/IR/IRBuilder.h:147:30
#9 0xfffffffff393b6d0 expandAtomicCmpXchg ../lib/CodeGen/AtomicExpandPass.cpp:1246:27
#10 0xfffffffff633c02b (/lib/
Segmentation fault (core dumped)

I can also confirm this with llvm8.0-8.0.0-11.fc31.x86_64:

$ llc-8.0 load.ll
Stack dump:
0.      Program arguments: llc-8.0 load.ll
1.      Running pass 'Function Pass Manager' on module 'load.ll'.
2.      Running pass 'Expand Atomic instructions' on function '@unordered_load'
#0 0x00007f92dc934d0e llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/usr/lib64/llvm8.0/lib/
#1 0x00007f92dc932d84 llvm::sys::RunSignalHandlers() (/usr/lib64/llvm8.0/lib/
#2 0x00007f92dc932f05 (/usr/lib64/llvm8.0/lib/
#3 0x00007f92dbaef6b0 __restore_rt (/lib64/
#4 0x00007f92dc755172 (/usr/lib64/llvm8.0/lib/
#5 0x00007ffdcbec1278
Segmentation fault (core dumped)

It also crashes with llc-7.0, but llc from llvm-9.0.0-1.fc31.x86_64 is okay.

Comment 3 Josh Stone 2020-02-01 04:35:54 UTC
I bisected to this:

    [AtomicExpand] Fix a crash bug when lowering unordered loads to cmpxchg

    Add tests for wider atomic loads and stores.  In the process, fix a crasher where we appearently handled unorder stores, but not loads, when lowering to cmpxchg idioms.

    llvm-svn: 356482

I'd say that fits!

Comment 5 Fedora Update System 2020-02-04 01:22:05 UTC
FEDORA-2020-5739bd54c3 has been submitted as an update to Fedora 30.

Comment 6 Fedora Update System 2020-02-05 00:52:34 UTC
llvm-8.0.0-7.fc30, rust-1.41.0-1.fc30, rust-packaging-10-2.fc30 has been pushed to the Fedora 30 testing repository. If problems still persist, please make note of it in this bug report.
See for
instructions on how to install test updates.
You can provide feedback for this update here:

Comment 7 Fedora Update System 2020-02-20 04:45:44 UTC
llvm-8.0.0-7.fc30, rust-1.41.0-1.fc30, rust-packaging-10-2.fc30 has been pushed to the Fedora 30 stable repository. If problems still persist, please make note of it in this bug report.

Comment 8 Josh Stone 2020-02-27 22:05:42 UTC
The update reached stable a week ago.