dumping llvm bitcode from cicc

method 1

requires building of hijacked .so with appropriate LLVM version. I am too lazy for this

 

method 2

cool, but does not work - cicc claims on bad arguments. I've tried many combinations with no luck

 

But hey - we are under linux and can make many hacks, for example check what arguments genuine nvcc passing to cicc. For this I ran nvcc -dc -keep under strace:

strace -o c.strace -s 512 -f --trace=/^exec nvcc ...


Arguments:

• -s NUM - maximum string size, bcs arguments can be very long - I set this parameter to 512
• -f - trace child processes
• and finally --trace - since I don't know which exactly syscall used to launch processes I used regex syntax for all calls starting with exec

Lets check output file c.strace and see launches of

• gcc/cc1plus
• cicc
• ptxas
• fatbinary
• bin2c
• cudafe++
• etc
  

After some trials right combination of arguments for cicc is
NVVMCCWIZ=553282 cicc --nv_arch compute_XX --device-c -keep 1.cpp1.ii
ls -l *.bc
-rw-rw-r-- 1 redp redp 8072 mar 31 13:25 1.lgenfe.bc
-rw-rw-r-- 1 redp redp 9988 mar 31 13:25 1.lnk.bc
-rw-rw-r-- 1 redp redp 6500 mar 31 13:25 1.opt.bc

lgenfe.bc - bitcode from front-end

opt.bc - bitcode after all optimization passes

to disassembly we can now just use llvm-dis-21:

  %1 = tail call i32 asm sideeffect "activemask.b32 $0;", "=r"() #3, !dbg !11
  %2 = tail call { i32, i1 } @llvm.nvvm.shfl.sync.i32(i32 %1, i32 3, i32 %val, i32 16, i32 31) #3, !dbg !17
  %3 = extractvalue { i32, i1 } %2, 0, !dbg !17