Calling external functions failed on PowerPC

Project Infrastructure LLVM Dev List Archives
1

Hi, all

  I have a trouble with calling external functions on PowerPC.
What I am doing is generating a LLVM IR first like this,

- x86

call void @helper_shack_flush(%struct.CPUX86State* %62) noinline, !flags !12

- ppc

call void @helper_shack_flush(%struct.CPUX86State* %62) noinline, !flags !10
   
After lowering above LLVM IR for x86 and ppc, it becomes:

- x86

%RAX<def> = MOV64ri <ga:@helper_shack_flush>
%RDI<def> = COPY %RBX
CALL64r %RAX<kill>, %RDI<kill>, %RAX<imp-def,dead>,
%RCX<imp-def,dead>, %RDX<imp-def,dead>, %RSI<imp-def,dead>,
%%RDI<imp-def,dead>, %R8<imp-def,dead>,
%EFLAGS<imp-def,dead>, %RSP<imp-use>, ...

- ppc

%X4<def> = LDtoc <ga:@helper_shack_flush>, %X2

  The x86 JIT can call the external function correctly, but
the ppc JIT give me the error belows,

  %X4<def> = LDtoc <ga:@helper_shack_flush>, %X2
UNREACHABLE executed!
Stack dump:
0. Running pass 'PowerPC Machine Code Emitter' on function '@"8048150"'
Aborted

  Is this a bug in ppc JIT? Or I have to do something else
so that ppc JIT can call external functions?

  Thanks!

Regards,
chenwj

2

Hi, all

  I found the example code examples/HowToUseJIT.cpp also shows
the same error.

  Attachment is the LLVM module created by HowToUseJIT. And here
is the error,

Running foo: %X4<def> = LDtoc <ga:@add1>, %X2
UNREACHABLE executed!
Stack dump:
0. Running pass 'PowerPC Machine Code Emitter' on function '@foo'
Aborted

  Currently, I use gdb try to track down where the problem is. Here
is the backtrace,

(gdb) bt
#0 0x00000fffb7b84090 in .raise () from /lib/libc.so.6
#1 0x00000fffb7b85ca4 in .abort () from /lib/libc.so.6
#2 0x0000000010517b9c in ._ZN4llvm25llvm_unreachable_internalEPKcS1_j ()
#3 0x0000000010047aa0 in ._ZN12_GLOBAL__N_114PPCCodeEmitter17getMachineOpValueERKN4llvm12MachineInstrERKNS1_14MachineOperandE ()
#4 0x0000000010048ff4 in ._ZN12_GLOBAL__N_114PPCCodeEmitter14emitBasicBlockERN4llvm17MachineBasicBlockE ()
#5 0x000000001004940c in ._ZN12_GLOBAL__N_114PPCCodeEmitter20runOnMachineFunctionERN4llvm15MachineFunctionE ()
#6 0x00000000101f26f4 in ._ZN4llvm19MachineFunctionPass13runOnFunctionERNS_8FunctionE ()
#7 0x00000000104b8634 in ._ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE ()
#8 0x00000000104b883c in ._ZN4llvm23FunctionPassManagerImpl3runERNS_8FunctionE ()
#9 0x00000000104b8b1c in ._ZN4llvm19FunctionPassManager3runERNS_8FunctionE ()
#10 0x0000000010020f64 in ._ZN4llvm3JIT14jitTheFunctionEPNS_8FunctionERKNS_10MutexGuardE ()
#11 0x0000000010021314 in ._ZN4llvm3JIT24runJITOnFunctionUnlockedEPNS_8FunctionERKNS_10MutexGuardE ()
#12 0x000000001002155c in ._ZN4llvm3JIT20getPointerToFunctionEPNS_8FunctionE ()
#13 0x00000000100236e4 in ._ZN4llvm3JIT11runFunctionEPNS_8FunctionERKSt6vectorINS_12GenericValueESaIS4_EE ()
#14 0x000000001000918c in main () at HowToUseJIT.cpp:116

  Any idea how can I further spot where is the bug? Thanks!

Regards,
chenwj

3

Forgot the attachment, sorry.

HowToUseJIT.txt (232 Bytes)

4

Hi, folks

  I saw the comments at the top of PowerPC/PPCCodeEmitter.cpp,
the ppc JIT is for PowerPC32 machine. But I am running a PowerPC64
machine. Could it be the reason why the ppc JIT cannot call external
functions?

  Thanks!

Regards,
chenwj

5

Hi, all

  I found the example code examples/HowToUseJIT.cpp also shows
the same error.

  At the end of inserting instruction into the Module created in
HowToUseJIT.cpp, I call function verifyModule to verify if everything
is O.K.. This time, it gave me much readable output,

Running foo: HowToUseJIT: /tmp/chenwj/llvm-2.8/lib/Target/PowerPC/PPCCodeEmitter.cpp:156: unsigned int<unnamed>::PPCCodeEmitter::getMachineOpValue(const
llvm::MachineInstr&, const llvm::MachineOperand&): Assertion `MovePCtoLROffset && "MovePCtoLR not seen yet?"' failed.
Stack dump:
0. Running pass 'PowerPC Machine Code Emitter' on function '@foo'
Aborted

  The assert comes from PPCCodeEmitter.cpp.

if (TM.getRelocationModel() == Reloc::PIC_) {
  assert(MovePCtoLROffset && "MovePCtoLR not seen yet?");
}

  Which direction I should look into? Thanks!

Regards,
chenwj