fatal error: error in backend: Cannot select: 0x7fffe4f5a020: ch = store<(store (s256) into %ir.30 + 32, align 8)> 0x7fffe4f97a20, 0x7fffe4f96de0, 0x7fffe4fddcc0, undef:i64

[yzewei]

Clang front-end optimizer compilation error.

• Environment: compiler: clang-17 arch: loongarch64 os: alpine-linux
• Error:

  
  2024-05-25 06:06:43,903 root INFO clang -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -Os -fstack-clash-protection -Wformat -Werror=format-security -fPIC -I. -I/home/alpine/aports/testing/highctidh/src/highctidh/src -I/usr/include/python3.12 -c csidh.c -o build/tmp/csidh.o -Wextra -Wall -fpie -fPIC -fwrapv -pedantic -O2 -g0 -fno-lto -DGETRANDOM -DPLATFORM=loongarch64 -DPLATFORM_SIZE=64 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -fstack-protector-strong -Wno-ignored-optimization-argument -Wno-unreachable-code -march=native -mtune=native -DHIGHCTIDH_PORTABLE=1 -DBITS=511 -DNAMESPACEBITS(x)=highctidh_511_##x -DNAMESPACEGENERIC(x)=highctidh_##x
  clang: warning: argument unused during compilation: '-fno-strict-overflow' [-Wunused-command-line-argument]
  clang: warning: argument unused during compilation: '-fstack-clash-protection' [-Wunused-command-line-argument]
  fatal error: error in backend: Cannot select: 0x7fffe4f5a020: ch = store<(store (s256) into %ir.30 + 32, align 8)> 0x7fffe4f97a20, 0x7fffe4f96de0, 0x7fffe4fddcc0, undef:i64
  0x7fffe4f96de0: v4i64,ch = load<(dereferenceable load (s256) from @highctidh_511_fp_1 + 32, align 8)> 0x7fffe4df2ca0, 0x7fffe4fddb70, undef:i64
  0x7fffe4fddb70: i64 = add 0x7fffe4fddd30, Constant:i64<32>
    0x7fffe4fddd30: i64 = PseudoLA_GOT TargetGlobalAddress:i64<ptr @highctidh_511_fp_1> 0
      0x7fffe4fdea50: i64 = TargetGlobalAddress<ptr @highctidh_511_fp_1> 0
    0x7fffe4f97b00: i64 = Constant<32>
  0x7fffe4f97940: i64 = undef
  0x7fffe4fddcc0: i64 = add FrameIndex:i64<1>, Constant:i64<96>
  0x7fffe4f97550: i64 = FrameIndex<1>
  0x7fffe4fe5370: i64 = Constant<96>
  0x7fffe4f97940: i64 = undef
  In function: highctidh_511_action
  PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
  Stack dump:
  0.  Program arguments: /usr/bin/clang -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -Os -fstack-clash-protection -Wformat -Werror=format-security -fPIC -I. -I/home/alpine/aports/testing/highctidh/src/highctidh/src -I/usr/include/python3.12 -c csidh.c -o build/tmp/csidh.o -Wextra -Wall -fpie -fPIC -fwrapv -pedantic -O2 -g0 -fno-lto -DGETRANDOM -DPLATFORM=loongarch64 -DPLATFORM_SIZE=64 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -fstack-protector-strong -Wno-ignored-optimization-argument -Wno-unreachable-code -march=native -mtune=native -DHIGHCTIDH_PORTABLE=1 -DBITS=511 -DNAMESPACEBITS(x)=highctidh_511_##x -DNAMESPACEGENERIC(x)=highctidh_##x
  1.  <eof> parser at end of file
  2.  Code generation
  3.  Running pass 'Function Pass Manager' on module 'csidh.c'.
  4.  Running pass 'LoongArch DAG->DAG Pattern Instruction Selection' on function '@highctidh_511_action'
  clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
  Alpine clang version 17.0.6
  Target: loongarch64-alpine-linux-musl
  Thread model: posix
  InstalledDir: /usr/bin
  Configuration file: /etc/clang17/loongarch64-alpine-linux-musl.cfg
  clang: note: diagnostic msg: 
  ********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT: Preprocessed source(s) and associated run script(s) are located at: clang: note: diagnostic msg: /tmp/csidh-a7a0a9.c clang: note: diagnostic msg: /tmp/csidh-a7a0a9.sh clang: note: diagnostic msg:

[xen0n]

This is because the LSX codegen support in LLVM 17 is incomplete, so if one passes a march implicitly enabling LSX / LASX, one risks encountering such unimplemented code path. Other users have run into similar issues as well.

Ideally we would have disabled LSX/LASX codegen for LLVM 17, but for now one can simply reduce their march setting to generic or loongarch64 so as to avoid SIMD instructions. LLVM 18 onwards should be fine.