1.13.0 armhf stage0 segfaults when building 1.14.0

[infinity0]

No logs available, I ran this manually on harris.debian.org. This machine has NEON enabled, to work around #36913. But it should produce 1.14.0 armhf host binaries that don't need NEON (as discussed in #35590).

This is after applying #38650 and #38675; The LLVM diff between Debian vs Rust is here.

There are some ARM-related LLVM patches that we haven't yet applied in Debian (see here), however this error is in the stage0 compiler so it is probably not Debian-specific. (Though it could be that the stage0 compiler itself is buggy, and needs to be recompiled with these LLVM patches.)

CFG_LLVM_LINKAGE_FILE=/home/infinity0/rustc/armv7-unknown-linux-gnueabihf/rt/llvmdeps.rs LD_LIBRARY_PATH=/home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/lib:/usr/lib/llvm-3.9/lib:$LD_LIBRARY_PATH   armv7-unknown-linux-gnueabihf/stage0/bin/rustc --cfg stage0 -C link-args=-Wl,-z,relro -O --cfg rtopt -Cdebuginfo=1 -C rpath -C prefer-dynamic -C no-stack-check --target=armv7-unknown-linux-gnueabihf   -L "armv7-unknown-linux-gnueabihf/rt" -L native="/usr/lib/llvm-3.9/lib"     --out-dir armv7-unknown-linux-gnueabihf/stage0/lib/rustlib/armv7-unknown-linux-gnueabihf/lib -C extra-filename=-f5a209a9 -C metadata=f5a209a9 src/libcore/lib.rs
warning: this feature has been stable since 1.14.0. Attribute no longer needed, #[warn(stable_features)] on by default
  --> src/libcore/lib.rs:92:29
   |
92 | #![cfg_attr(stage0, feature(question_mark))]
   |                             ^^^^^^^^^^^^^

Segmentation fault
/home/infinity0/rustc/mk/target.mk:191: recipe for target 'armv7-unknown-linux-gnueabihf/stage0/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/stamp.core' failed

Re-running manually for a stack trace:

rustc$ RUSTC_BOOTSTRAP=1 RUSTC_BOOTSTRAP_KEY=62b3e239 CFG_LLVM_LINKAGE_FILE=/home/infinity0/rustc/armv7-unknown-linux-gnueabihf/rt/llvmdeps.rs LD_LIBRARY_PATH=/home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/lib:/usr/lib/llvm-3.9/lib:$LD_LIBRARY_PATH  gdb armv7-unknown-linux-gnueabihf/stage0/bin/rustc
GNU gdb (Debian 7.12-4) 7.12
[..]
(gdb) run --cfg stage0 -C link-args=-Wl,-z,relro -O --cfg rtopt -Cdebuginfo=1 -C rpath -C prefer-dynamic -C no-stack-check --target=armv7-unknown-linux-gnueabihf   -L "armv7-unknown-linux-gnueabihf/rt" -L native="/usr/lib/llvm-3.9/lib"     --out-dir armv7-unknown-linux-gnueabihf/stage0/lib/rustlib/armv7-unknown-linux-gnueabihf/lib -C extra-filename=-f5a209a9 -C metadata=f5a209a9 src/libcore/lib.rs
Starting program: /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/rustc --cfg stage0 -C link-args=-Wl,-z,relro -O --cfg rtopt -Cdebuginfo=1 -C rpath -C prefer-dynamic -C no-stack-check --target=armv7-unknown-linux-gnueabihf   -L "armv7-unknown-linux-gnueabihf/rt" -L native="/usr/lib/llvm-3.9/lib"     --out-dir armv7-unknown-linux-gnueabihf/stage0/lib/rustlib/armv7-unknown-linux-gnueabihf/lib -C extra-filename=-f5a209a9 -C metadata=f5a209a9 src/libcore/lib.rs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
[New Thread 0xb3dff270 (LWP 15815)]
warning: this feature has been stable since 1.14.0. Attribute no longer needed, #[warn(stable_features)] on by default
  --> src/libcore/lib.rs:92:29
   |
92 | #![cfg_attr(stage0, feature(question_mark))]
   |                             ^^^^^^^^^^^^^


Thread 2 "rustc" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb3dff270 (LWP 15815)]
0xb51a2974 in llvm::LiveRangeEdit::scanRemattable(llvm::AAResults*) () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
(gdb) bt
#0  0xb51a2974 in llvm::LiveRangeEdit::scanRemattable(llvm::AAResults*) () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#1  0xb51a29ee in llvm::LiveRangeEdit::anyRematerializable(llvm::AAResults*) () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#2  0xb528c72e in llvm::SplitEditor::reset(llvm::LiveRangeEdit&, llvm::SplitEditor::ComplementSpillMode) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#3  0xb5247154 in (anonymous namespace)::RAGreedy::selectOrSplitImpl(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&, llvm::SmallSet<unsigned int, 16u, std::less<unsigned int> >&, unsigned int) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#4  0xb52465e2 in (anonymous namespace)::RAGreedy::selectOrSplitImpl(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&, llvm::SmallSet<unsigned int, 16u, std::less<unsigned int> >&, unsigned int) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#5  0xb52465e2 in (anonymous namespace)::RAGreedy::selectOrSplitImpl(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&, llvm::SmallSet<unsigned int, 16u, std::less<unsigned int> >&, unsigned int) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#6  0xb52465e2 in (anonymous namespace)::RAGreedy::selectOrSplitImpl(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&, llvm::SmallSet<unsigned int, 16u, std::less<unsigned int> >&, unsigned int) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#7  0xb52465e2 in (anonymous namespace)::RAGreedy::selectOrSplitImpl(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&, llvm::SmallSet<unsigned int, 16u, std::less<unsigned int> >&, unsigned int) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#8  0xb5247992 in (anonymous namespace)::RAGreedy::selectOrSplit(llvm::LiveInterval&, llvm::SmallVectorImpl<unsigned int>&) ()
   from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#9  0xb523a9a0 in llvm::RegAllocBase::allocatePhysRegs() () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#10 0xb5244c54 in (anonymous namespace)::RAGreedy::runOnMachineFunction(llvm::MachineFunction&) () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
#11 0xb51da24a in llvm::MachineFunctionPass::runOnFunction(llvm::Function&) () from /home/infinity0/rustc/armv7-unknown-linux-gnueabihf/stage0/bin/../lib/../lib/librustc_llvm-91a6b62b230b4784.so
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) 

[brson]

Thanks for filing these tier 2 platform bugs @infinity0 .

I'd guess this is the same as #37813

[infinity0]

Following the links, this comment explains the issue and it seems simplest if we in Debian just wait for the next version in order to bootstrap armhf.