[LLVMdev] bytecode reader assertion failure

[Ryan M. Lefever]

I have a compiler transform that I have been working on that produces 
bytecode that passes the verifier.  However, when I try to read that 
bytecode back in, I get the assertion failure below.

llvm::BytecodeReader::ParseConstantPoolValue(unsigned int):
Assertion `(!isa<Constant>(Result) || 
!cast<Constant>(Result)->isNullValue()) || !hasImplicitNull(TypeID) && 
"Cannot read null values from bytecode!"' failed.

So, I ran gdb on opt.  I was able to get the following information from opt:

(gdb) print Result
$7 = (class llvm::Constant *) 0x96ad9d0
(gdb) call Result->dump()
  [41 x sbyte *] zeroinitializer
(gdb) print hasImplicitNull(TypeID)
$5 = true

Does anyone have any insight into what the problem is or how to go about 
  fixing it?  It seems diffcult to get context for what is going on, 
since the bytecode has not yet been fully read.  Any help would be 
greatly appreciated!

The full output of the assertion failure is given below:

opt -simplifycfg -deadargelim -globaldce -verify -f -o /dev/null tmp.bc
opt: Reader.cpp:1978: llvm::Value* 
llvm::BytecodeReader::ParseConstantPoolValue(unsigned int): Assertion 
`(!isa<Constant>(Result) || !cast<Constant>(Result)->isNullValue()) || 
!hasImplicitNull(TypeID) && "Cannot read null values from bytecode!"' 
failed.
opt((anonymous namespace)::PrintStackTrace()+0x1a)[0x8645bae]
opt((anonymous namespace)::SignalHandler(int)+0x112)[0x8645e74]
[0xb87420]
/lib/libc.so.6(abort+0x101)[0x4cab64f1]
/lib/libc.so.6(__assert_fail+0xfd)[0x4caae859]
opt(llvm::BytecodeReader::ParseConstantPoolValue(unsigned 
int)+0x1b31)[0x856e825]
opt(llvm::BytecodeReader::ParseConstantPool(std::vector<llvm::BytecodeReader::ValueList*, 
std::allocator<llvm::BytecodeReader::ValueList*> >&, 
std::vector<llvm::PATypeHolder, std::allocator<llvm::PATypeHolder> >&, 
bool)+0x147)[0x856e985]
opt(llvm::BytecodeReader::ParseModule()+0x188)[0x856edfe]
opt(llvm::BytecodeReader::ParseBytecode(unsigned char const*, unsigned 
int, std::basic_string<char, std::char_traits<char>, 
std::allocator<char> > const&, std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >*)+0x539)[0x856f6c1]
opt((anonymous 
namespace)::BytecodeFileReader::read(std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >*)+0xeb)[0x855b569]
opt(llvm::getBytecodeModuleProvider(std::basic_string<char, 
std::char_traits<char>, std::allocator<char> > const&, 
std::basic_string<char, std::char_traits<char>, std::allocator<char> >*, 
llvm::BytecodeHandler*)+0x93)[0x855b60b]
opt(llvm::ParseBytecodeFile(std::basic_string<char, 
std::char_traits<char>, std::allocator<char> > const&, 
std::basic_string<char, std::char_traits<char>, std::allocator<char> 
 >*)+0x20)[0x855b88e]
opt(main+0x7e)[0x8378c90]
/lib/libc.so.6(__libc_start_main+0xdc)[0x4caa24e4]
opt(__gxx_personality_v0+0x149)[0x836bac1]


Regards,
Ryan