Clang for RISC-V 32/64 bits crashes on __c11_atomic_*_fence() with variable memory order

[EdSchouten]

Hi there,

The following piece of code:

int main(int argc, char **argv) {
  __c11_atomic_signal_fence(argc);
}

causes Clang r318692 with today's patches to crash as follows:

fatal error: error in backend: Cannot select: 0x8066806e8: ch = AtomicFence 0x80661cc40, Constant:i64<7>,
      Constant:i64<0>
  0x806680548: i64 = Constant<7>
  0x806680068: i64 = Constant<0>
In function: main
clang-6.0: error: clang frontend command failed with exit code 70 (use -v to see invocation)
clang version 6.0.0 (trunk 318692)
Target: riscv64-unknown-cloudabi
Thread model: posix
InstalledDir: /usr/local/bin
clang-6.0: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
clang-6.0: note: diagnostic msg: 
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PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-6.0: note: diagnostic msg: /tmp/bla-aa1f6f.c
clang-6.0: note: diagnostic msg: /tmp/bla-aa1f6f.sh
clang-6.0: note: diagnostic msg: 

********************

Best regards,
Ed