[llvm-bugs] [Bug 26108] New: Compiling kernel bpf samples with -O0 results in error

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26108

            Bug ID: 26108
           Summary: Compiling kernel bpf samples with -O0 results in error
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: prb003 at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

compiling samples/bpf/ from linux kernel with change in optimization as -O0
results in following error. Though with -O2 (which is default in Makefile)
works fine.

$ make samples/bpf/
[...]
clang  -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include
-I./arch/x86/include -Iarch/x86/include/generated/uapi
-Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
-Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi
-include ./include/linux/kconfig.h  \
    -D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
    -O0 -emit-llvm -c samples/bpf/tracex1_kern.c -o -| /home/ravi/bin/llc
-march=bpf -filetype=obj -o samples/bpf/tracex1_kern.o
LLVM ERROR: Cannot select: t12: ch,glue = BPFISD::CALL t11, t6, Register:i64
%R1, t11:1
  t6: i64,ch = load<LD8[getelementptr inbounds (%struct.smp_ops,
%struct.smp_ops* @smp_ops, i32 0, i32 3)]> t0, t3, undef:i64
    t3: i64 = add t16, Constant:i64<24>
      t16: i64 = BPFISD::Wrapper TargetGlobalAddress:i64<%struct.smp_ops*
@smp_ops> 0
        t15: i64 = TargetGlobalAddress<%struct.smp_ops* @smp_ops> 0
      t2: i64 = Constant<24>
    t5: i64 = undef
  t10: i64 = Register %R1
  t11: ch,glue = CopyToReg t9, Register:i64 %R1, Constant:i64<0>
    t10: i64 = Register %R1
    t4: i64 = Constant<0>
In function: smp_send_stop
samples/bpf/Makefile:66: recipe for target 'samples/bpf/tracex1_kern.o' failed
make[1]: *** [samples/bpf/tracex1_kern.o] Error 1
Makefile:1544: recipe for target 'samples/bpf/' failed
make: *** [samples/bpf/] Error 2
$

Experimented on,
Linux kernel version : 4.4
Architecture : x86
clang version : 3.8.0 (trunk 256744)
llc version : 3.8.0svn

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