[LLVMdev] Assertion failure in llc when using exception handling

[Shivram Khandeparker]

Hi,

I'm trying to compile an llvm program which makes use of exception handling.
While compiling the code with llc i get the following assertion failure

llc: FunctionLoweringInfo.cpp:163: void llvm::FunctionLoweringInfo::clear():
Assertion `CatchInfoFound.size() == CatchInfoLost.size() && "Not all catch
info was assigned to a landing pad!"' failed.
0  llc             0x0000000000d5d23f
1  llc             0x0000000000d5f026
2  libpthread.so.0 0x00007f47688d38f0
3  libc.so.6       0x00007f4767bc3a75 gsignal + 53
4  libc.so.6       0x00007f4767bc75c0 abort + 384
5  libc.so.6       0x00007f4767bbc941 __assert_fail + 241
6  llc             0x00000000008a5a19 llvm::FunctionLoweringInfo::clear() +
1353
7  llc             0x00000000009364de
llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) + 3102
8  llc             0x0000000000ce828f
llvm::FPPassManager::runOnFunction(llvm::Function&) + 671
9  llc             0x0000000000ce834b
llvm::FPPassManager::runOnModule(llvm::Module&) + 75
10 llc             0x0000000000ce7d84
llvm::MPPassManager::runOnModule(llvm::Module&) + 564
11 llc             0x0000000000ce7ee0
llvm::PassManagerImpl::run(llvm::Module&) + 160
12 llc             0x0000000000565941 main + 3009
13 libc.so.6       0x00007f4767baec4d __libc_start_main + 253
14 llc             0x0000000000563849
Stack dump:
0. Program arguments: llc b.bc
1. Running pass 'Function Pass Manager' on module 'b.bc'.
2. Running pass 'X86 DAG->DAG Instruction Selection' on function '@main'
Aborted

I only get this error when the b.bc file is generated with opt -O3. The
program compiles and executes just fine with opt -O2. I was able to find out
the minimum number of optimization passes that cause this crash. They are

opt -inline -jump-threading -instcombine -licm -loop-unswitch -o b.bc a.bc

I'm attaching the original unoptimized file a.bc.gz and the optimized
version b.bc.gz. I apologize for sending in such large files, but I just
couldn't reproduce this problem with smaller programs. By putting some debug
statements in llc I was able to narrow the problem in b.bc down to following
lines of code

Unwind.i74.i.i:                                   ; preds =
%normal44.i79.i.i
  %153 = call i8* @llvm.eh.exception()            ; <i8*> [#uses=2]
  %154 = call i32 (i8*, i8*, ...)* @llvm.eh.selector(i8* %153, i8* bitcast
(i32 (...)* @__gxx_personality_v0 to i8*),
 i8* null) ; <i32> [#uses=0]
  invoke void @_Unwind_Resume_or_Rethrow(i8* %153)
          to label %.noexc83.i.i unwind label %lpad51.preheader.i.i

lpad51.preheader.i.i:                             ; preds = %Unwind.i74.i.i,
%Unwind.i61.i.i
  %155 = icmp eq i8* %58, null                    ; <i1> [#uses=1]
  %156 = bitcast i8* %61 to %File*                ; <%File*> [#uses=1]
  br i1 %155, label %Unwind.loopexit.us-lcssa.us.i.i, label %normal31.i.i.i

Unwind.loopexit.us-lcssa.us.i.i:                  ; preds =
%lpad51.preheader.i.i
  %157 = call i8* @llvm.eh.exception()            ; <i8*> [#uses=2]
  %158 = call i32 (i8*, i8*, ...)* @llvm.eh.selector(i8* %157, i8* bitcast
(i32 (...)* @__gxx_personality_v0 to i8*), i8* null) ; <i32> [#uses=0]
  br label %Unwind.i.i


The Unwind.loopexit.us-lcssa.us.i.i landing pad gets added to CatchInfoLost
but not to CatchInfoFound which causes the assertion to fail. I have also
attached the output from bugpoint -run-llc b.bc

Is there something wrong with the original ll code I am generating?

I will be glad to provide more information.

Thanks,
Shivram
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