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Summary

Bootstrapping a riscv64 toolchain on x64 results in some unusable stage2 binaries.

Steps to reproduce

0. Create a working directory (e.g. ~/build) and clone the ghc repository into it.

1. Prepare a Debian sid x64 chroot (I am using debian-sid-tar from https://hub.nspawn.org/images/).

2. Mount the directory inside the chroot and start it. Personally I found it very simple with systemd-nspawn:

   systemd-nspawn -D /path/to/debian/x64 --bind=~/build:/build

3. Install required tools in the chroot (git, build-essential, gcc-12, autoconf, python3, riscv64-linux-gnu-gcc, llvm-12, ghc 8.10.6 from experimental, happy, alex).

4. Build the ghc-9.2 branch with !6765 (merged) because rv64 gcc requires explicitly linking to libatomic for sub-word atomic operations.

   (debian-sid-x64-chroot) $ ./boot
   (debian-sid-x64-chroot) $ ./configure --target=riscv64-linux-gnu
   (debian-sid-x64-chroot) $ make

   build.mk:

   ...
   BuildFlavour = quick
   ...
   WITH_TERMINFO         = NO
   BUILD_EXTRA_PKGS      = NO
   HADDOCK_DOCS          = NO
   BUILD_MAN             = NO
   BUILD_SPHINX_HTML     = NO
   BUILD_SPHINX_PDF      = NO
   
   GhcRtsCcOpts += -fkeep-inline-functions
   DYNAMIC_GHC_PROGRAMS  =  NO
   GhcLibWays = v
   GhcRTSWays = debug
   GhcThreaded = NO
   GhcDebugged = YES

5. Setup qemu-user-static and binfmt-misc, and prepare a riscv64 chroot (may refer to this Debian wiki article, starting from the "Qemu" section).

6. Mount the working directory into the chroot and start it:

   systemd-nspawn -D /path/to/debian/rv64 --bind=~/build:/build

7. Try to execute the stage2 binary:

   (debian-rv64-chroot) $ inplace/bin/ghc-stage2
   ghc-stage2: internal error: ASSERTION FAILED: file rts/dist/build/AutoApply.cmm, line 2317
   
       (GHC version 9.2.0.20211020 for riscv64_unknown_linux)
       Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug
   Aborted (core dumped)

   A more detailed log, with +RTS -Di -Da -Ds -DS, can be found at https://ix.io/3CkH.

   I've also tried to pull in 8b5e5b05 and cb862ecf (the branch is at https://gitlab.haskell.org/hexchain/ghc/-/tree/ghc-9.2-rv64-bootstrap). The compiler still crashes, but only with a "Segmentation fault". With +RTS -Di -Da -Ds -DS there is not much difference.

Expected behavior

The stage2 binary should work without any problem.

Environment

• GHC version used: 8.10.6 (from debian experimental)
• LLVM: 12.0
• GCC: riscv64-linux-gnu-gcc 11.2.0

Optional:

• Operating System: Arch Linux
• System Architecture: x64