Dear developers:
When I am doing basicblock pass, I meet a bug: there is an iterator "I" in a basicblock, and it is not pointing to the first instruction in this basicblock. However, "I--;" will fail by an assertion.
The basic block ("I" is pointing to the second instruction) in test.ll:
bb: ; preds = %bb1
%1 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([42 x i8]* @.str1, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
%2 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([40 x i8]* @.str2, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
%3 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([40 x i8]* @.str3, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
%4 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([42 x i8]* @.str, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
br label %bb1
The code slice in verify-fixrace.cpp in attachment:
cerr << "IsFirst Current Inst: " << *I;
cerr << "IsFirst First Inst: " << *BB->begin();
I--;
Output is:
Inst: %2 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([40 x i8]* @.str2, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
Backward Visit BB: bb
IsFirst Current Inst: %2 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([40 x i8]* @.str2, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
IsFirst First Inst: %1 = call i32 (i8*, ...)* @printf(i8* noalias getelementptr ([42 x i8]* @.str1, i32 0, i32 0)) nounwind ; <i32> [#uses=0]
opt: /home/heming/defens/llvm-2.5/include/llvm/ADT/ilist.h:173: llvm::ilist_iterator<NodeTy>& llvm::ilist_iterator<NodeTy>::operator--() [with NodeTy = llvm::Instruction]: Assertion `Traits::getNext(NodePtr) && "--'d off the beginning of an ilist!"' failed.
0 opt 0x08642be4
1 opt 0x08642f26
2 0xb7f7f420 __kernel_sigreturn + 0
3 libc.so.6 0xb7d0ca01 abort + 257
4 libc.so.6 0xb7d0410e __assert_fail + 238
5 opt 0x08357997 llvm::ilist_iterator<llvm::Instruction>::operator--() + 87
6 opt 0x08367104 llvm::ilist_iterator<llvm::Instruction>::operator--(int) + 28
7 verify-fixrace-stub.so 0xb7f781be defens::verify_fixrace_stub::DFSBackward(llvm::Instruction*, std::string&, int, bool) + 826
8 verify-fixrace-stub.so 0xb7f78311 defens::verify_fixrace_stub::runOnBasicBlock(llvm::BasicBlock&) + 261
9 opt 0x085cdaf4
10 opt 0x085cee1c llvm::FPPassManager::runOnFunction(llvm::Function&) + 250
11 opt 0x085cefb8 llvm::FPPassManager::runOnModule(llvm::Module&) + 98
12 opt 0x085cd8a3 llvm::MPPassManager::runOnModule(llvm::Module&) + 197
13 opt 0x085cf256 llvm::PassManagerImpl::run(llvm::Module&) + 116
14 opt 0x085cf2af llvm::PassManager::run(llvm::Module&) + 27
15 opt 0x082f91d0 main + 4452
16 libc.so.6 0xb7cf6450 __libc_start_main + 224
17 opt 0x082e9c11 __gxx_personality_v0 + 849