LLVM Bug, BPF Target

foo-4e0928.c

# 1 "<built-in>"
# 1 "foo.c"

int do_request(long i) {
  char buf[100];
  int j;
  for(j = 0; j < i; j++) {
    buf[j] = 1;
  }
  return buf[j-1];
}

foo-4e0928.sh

# Crash reproducer for clang version 4.0.1-1 (tags/RELEASE_401/final)
# Driver args: "-v" "-g" "-O3" "--target=bpf" "-c" "foo.c" "-o" "foo.o"
# Original command:  "/usr/lib/llvm-4.0/bin/clang" "-cc1" "-triple" "bpf" "-emit-obj" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "foo.c" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-v" "-dwarf-column-info" "-debug-info-kind=limited" "-dwarf-version=4" "-debugger-tuning=gdb" "-coverage-notes-file" "/host/foo.gcno" "-resource-dir" "/usr/lib/llvm-4.0/bin/../lib/clang/4.0.1" "-O3" "-fdebug-compilation-dir" "/host" "-ferror-limit" "19" "-fmessage-length" "168" "-fobjc-runtime=gcc" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-vectorize-loops" "-vectorize-slp" "-o" "foo.o" "-x" "c" "foo.c"
 "/usr/lib/llvm-4.0/bin/clang" "-cc1" "-triple" "bpf" "-emit-obj" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "foo.c" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-v" "-dwarf-column-info" "-debug-info-kind=limited" "-dwarf-version=4" "-debugger-tuning=gdb" "-coverage-notes-file" "/host/foo.gcno" "-O3" "-ferror-limit" "19" "-fmessage-length" "168" "-fobjc-runtime=gcc" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-vectorize-loops" "-vectorize-slp" "-x" "c" "foo-4e0928.c"

foo.c

int do_request(long i) {
  char buf[100];
  int j;
  for(j = 0; j < i; j++) {
    buf[j] = 1;
  }
  return buf[j-1];
}

llvm-output

$ clang-4.0 -v -g -O3 -target bpf -c foo.c -o foo.o
clang version 4.0.1-1 (tags/RELEASE_401/final)
Target: bpf
Thread model: posix
InstalledDir: /usr/bin
 "/usr/lib/llvm-4.0/bin/clang" -cc1 -triple bpf -emit-obj -disable-free -disable-llvm-verifier -discard-value-names -main-file-name foo.c -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -v -dwarf-column-info -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -coverage-notes-file /host/foo.gcno -resource-dir /usr/lib/llvm-4.0/bin/../lib/clang/4.0.1 -O3 -fdebug-compilation-dir /host -ferror-limit 19 -fmessage-length 168 -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp -o foo.o -x c foo.c
clang -cc1 version 4.0.1 based upon LLVM 4.0.1 default target x86_64-pc-linux-gnu
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/llvm-4.0/bin/../lib/clang/4.0.1/include
 /usr/include
End of search list.
fatal error: error in backend: Cannot select: 0x55a879843468: ch,glue = BPFISD::CALL 0x55a879843128, TargetExternalSymbol:i64'memset', Register:i64 %R1, Register:i64
      %R2, Register:i64 %R3, 0x55a879843128:1
  0x55a879842ff0: i64 = TargetExternalSymbol'memset'
  0x55a8798437a8: i64 = Register %R1
  0x55a879843538: i64 = Register %R2
  0x55a879843330: i64 = Register %R3
  0x55a879843128: ch,glue = CopyToReg 0x55a879843398, Register:i64 %R3, 0x55a8798432c8, 0x55a879843398:1
    0x55a879843330: i64 = Register %R3
    0x55a8798432c8: i64,ch = CopyFromReg 0x55a8797e5c30, Register:i64 %vreg2
      0x55a8798436d8: i64 = Register %vreg2
    0x55a879843398: ch,glue = CopyToReg 0x55a879843670, Register:i64 %R2, Constant:i64<1>, 0x55a879843670:1
      0x55a879843538: i64 = Register %R2
      0x55a879843400: i64 = Constant<1>
      0x55a879843670: ch,glue = CopyToReg 0x55a879843058, Register:i64 %R1, FrameIndex:i64<0>
        0x55a8798437a8: i64 = Register %R1
        0x55a879843608: i64 = FrameIndex<0>
In function: do_request
clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
clang version 4.0.1-1 (tags/RELEASE_401/final)
Target: bpf
Thread model: posix
InstalledDir: /usr/bin
clang: 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: 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/foo-4e0928.c
clang: note: diagnostic msg: /tmp/foo-4e0928.sh
clang: note: diagnostic msg: 

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

It compiles with no optimizations.