[LLVMdev] JIT on ARM

[Martins Mozeiko]

Hi.
I am trying to run LLVM with JIT on ARM processor (Android phone).
Currently I have problems using external functions. Any call to external function crashes and gives me signal 11 (SIGSEGV) at some random address.

I'm trying to run following C code:
***
extern void add1(int* x);
int main()
{
    int a = 10;
    int b = 20;
    add1(&b);
    int c = a + b;
    return c;
}
***
It gives me following LL code:
***
define i32 @main() nounwind {
entry:
  %b = alloca i32, align 4                        ; <i32*> [#uses=3]
  store i32 20, i32* %b, align 4
  call void @add1(i32* %b) nounwind
  %0 = load i32* %b, align 4                      ; <i32> [#uses=1]
  %1 = add nsw i32 %0, 10                         ; <i32> [#uses=1]
  ret i32 %1
}

declare void @add1(i32*)
***
When using llvm::DebugFlag=true JIT gives me following debug messages:

********** Function: main

Ifcvt: function (0) 'main'
block 0 offset 0 size 40
block 0 offset 0 size 40
JITTing function 'main'
JIT: Starting CodeGen of Function main
JIT: Emitting BB0 at [0x4512e010]
JIT: 0x4512e010:	STM %SP, 12, 14, %reg0, %R11<kill>, %LR<kill>
  0xe92d4800
JIT: 0x4512e014:	%SP<def> = SUBri %SP<kill>, 8, 14, %reg0, %reg0
  0xe24dd008
JIT: 0x4512e018:	%R0<def> = MOVi 20, 14, %reg0, %reg0
  0xe3a00014
JIT: 0x4512e01c:	STR %R0<kill>, %SP, %reg0, 4, 14, %reg0, Mem:ST(4,4) [b + 0]
  0xe58d0004
JIT: 0x4512e020:	%R0<def> = ADDri %SP, 4, 14, %reg0, %reg0
  0xe28d0004
JIT: 0x4512e024:	BL <ga:add1>, %R0<kill>, %R0<imp-def,dead>, %R1<imp-def,dead>, %R2<imp-def,dead>, %R3<imp-def,dead>, %R12<imp-def,dead>, %LR<imp-def,dead>, %D0<imp-def,dead>, %D1<imp-def,dead>, %D2<imp-def,dead>, %D3<imp-def,dead>, %D4<imp-def,dead>, %D5<imp-def,dead>, %D6<imp-def,dead>, %D7<imp-def,dead>, %D16<imp-def,dead>, %D17<imp-def,dead>, %D18<imp-def,dead>, %D19<imp-def,dead>, %D20<imp-def,dead>, %D21<imp-def,dead>, %D22<imp-def,dead>, %D23<imp-def,dead>, %D24<imp-def,dead>, %D25<imp-def,dead>, %D26<imp-def,dead>, %D27<imp-def,dead>, %D28<imp-def,dead>, %D29<imp-def,dead>, %D30<imp-def,dead>, %D31<imp-def,dead>, %CPSR<imp-def,dead>
  0xeb000000
JIT: 0x4512e028:	%R0<def> = LDR %SP, %reg0, 4, 14, %reg0, Mem:LD(4,4) [b + 0]
  0xe59d0004
JIT: 0x4512e02c:	%R0<def> = ADDri %R0<kill>, 10, 14, %reg0, %reg0
  0xe280000a
JIT: 0x4512e030:	%SP<def> = ADDri %SP<kill>, 8, 14, %reg0, %reg0
  0xe28dd008
JIT: 0x4512e034:	LDM_RET %SP, 9, 14, %reg0, %R11<def>, %PC<def>
  0xe8bd8800
JIT: Map 'add1' to [0x808e80b4]
JIT: Stub emitted at [0x42540008] for function 'add1'
JIT: Finished CodeGen of [0x4512e010] Function: main: 40 bytes of text, 1 relocations
JIT: Binary code:
JIT: 00000000: e92d4800 e24dd008 e3a00014 e58d0004 
JIT: 00000010: e28d0004 eb5047f7 e59d0004 e280000a 
JIT: 00000020: e28dd008 e8bd8800 
****

Just to be sure I inform LLVM about add1 function with following code:
extern "C" void my_add1(int* x)
{
    LOG("in add1, x=%i\n", *x);
    *x = *x + 1;
}
sys::DynamicLibrary::AddSymbol("add1", (void*)&my_add1);

Is there something wrong with generated code? Same code, using same test program, runs fine using JIT on x86 under Windows.

I have successfuly run program that doesn't use external functions. For example following C code
****
int main()
{
    int a = 10;
    int b = 20;
    int c = a + b;
    return c;
}
****
compiles to following LL code:
****
define i32 @main() nounwind readnone {
entry:
  ret i32 30
}
****
which runs fine on ARM. When using llvm::DebugFlag=true JIT prints following debug messages:
********** Function: main

Ifcvt: function (0) 'main'
block 0 offset 0 size 8
block 0 offset 0 size 8
JITTing function 'main'
JIT: Starting CodeGen of Function main
JIT: Emitting BB0 at [0x4512e010]
JIT: 0x4512e010:	%R0<def> = MOVi 30, 14, %reg0, %reg0
  0xe3a0001e
JIT: 0x4512e014:	BX_RET 14, %reg0, %R0<imp-use,kill>
  0xe12fff1e
JIT: Finished CodeGen of [0x4512e010] Function: main: 8 bytes of text, 0 relocations
JIT: Binary code:
JIT: 00000000: e3a0001e e12fff1e 
***

I appreciate any suggestions what can I do in my situation.

--
Martins Mozeiko