[LLVMdev] How to access the return value of a CallInst

[Cong Wang]

Hi all:
    I am trying to get the return value of a call instruction that I
inserted during the optimization pass I wrote. I have something like
the following:

   CallInst *InitCall = CallInst::Create(InitFn, Args.begin(), Args.end(),
                                           "log_load_addr_ret", LI);
   CastInst *InsertedCast =
CastInst::CreateTruncOrBitCast(InitCall.getCalledValue(),
LI->getType(), "return_load", LI);

   I assume that getCalledValue() will give me the return value of the
InitCall CallInst.
   This compiles fine.
   But the CastInst cannot be created. The runtime error is :
opt: /panfs/panasas-01.cs.wisc.edu/scratch/wang/LLVM/src/llvm/lib/VMCore/Instructions.cpp:2338:
llvm::TruncInst::TruncInst(llvm::Value*, const llvm::Type*, const
llvm::Twine&, llvm::Instruction*): Assertion `castIsValid(getOpcode(),
S, Ty) && "Illegal Trunc"' failed.
0   opt             0x000000000084e8bf
1   opt             0x000000000084f37a
2   libpthread.so.0 0x000000310ac0e930
3   libc.so.6       0x000000310a030265 gsignal + 53
4   libc.so.6       0x000000310a031d10 abort + 272
5   libc.so.6       0x000000310a0296e6 __assert_fail + 246
6   opt             0x00000000007aad58
7   opt             0x00000000007aae33
llvm::CastInst::Create(llvm::Instruction::CastOps, llvm::Value*,
llvm::Type const*, llvm::Twine const&, llvm::Instruction*) + 211
8   opt             0x00000000004f4695
llvm::RSProfilers_std::InstrumentLoadStoreInBlock(llvm::BasicBlock*,
llvm::GlobalValue*, llvm::GlobalValue*, llvm::GlobalValue*,
llvm::GlobalValue*, llvm::GlobalValue*, llvm::GlobalValue*) + 4101
9   opt             0x00000000004ecb3f
10  opt             0x00000000007d5140
llvm::MPPassManager::runOnModule(llvm::Module&) + 464
11  opt             0x00000000007d76b5
llvm::PassManagerImpl::run(llvm::Module&) + 149
12  opt             0x00000000007d778d
llvm::PassManager::run(llvm::Module&) + 13
13  opt             0x000000000049c68b main + 2315
14  libc.so.6       0x000000310a01d994 __libc_start_main + 244
15  opt             0x0000000000492759 __gxx_personality_v0 + 393


   The goal of all this is to convert the return value to some other
form. The return value is always 64 bit int but I from time to time
needs other form, such a 32 bit int.
   Thanks for any input in advance.
-- 
Regards
James Wang
.-- .- -. --. @ -.-. ... .-.-.- .-- .. ... -.-. .-.-.- . -.. ..-