Stack:

0x007A84B0 (0x05D944A0 0x05D27F44 0x05D944A0 0x05D809B0), llvm::X86FrameLowering::emitEpilogue() + 0x60 bytes(s), d:\src\llvm\lib\target\x86\x86framelowering.cpp, line 1483 + 0x7 byte(s)
0x009D848A (0x00000001 0x05D94568 0x05D809B0 0x00000000), `anonymous namespace'::PEI::insertPrologEpilogCode() + 0x8A bytes(s), d:\src\llvm\lib\codegen\prologepiloginserter.cpp, line 977 + 0xA byte(s)
0x009D8C4B (0x041F9514 0x05D809B0 0x00000000 0x041F9514), `anonymous namespace'::PEI::runOnMachineFunction() + 0xDB bytes(s), d:\src\llvm\lib\codegen\prologepiloginserter.cpp, line 211
0x0094E871 (0x041F9514 0x041F9514 0x04150401 0x04190FF4), llvm::MachineFunctionPass::runOnFunction() + 0x31 bytes(s), d:\src\llvm\lib\codegen\machinefunctionpass.cpp, line 62
0x00A6DAC4 (0x041F9501 0x041910AC 0x00000000 0x0414ECA8), llvm::FPPassManager::runOnFunction() + 0xE4 bytes(s), d:\src\llvm\lib\ir\legacypassmanager.cpp, line 1522 + 0xA byte(s)
0x00A6DBA9 (0x04191020 0x05D690A0 0x00000000 0x04191020), llvm::FPPassManager::runOnModule() + 0x29 bytes(s), d:\src\llvm\lib\ir\legacypassmanager.cpp, line 1542
0x00A6DD19 (0x04191020 0x00000000 0x04190FF4 0x04190FF4), `anonymous namespace'::MPPassManager::runOnModule() + 0x159 bytes(s), d:\src\llvm\lib\ir\legacypassmanager.cpp, line 1599 + 0xD byte(s)
0x00A6D76A (0x04191020 0x0415D408 0x04191020 0x04154960), llvm::legacy::PassManagerImpl::run() + 0xAA bytes(s), d:\src\llvm\lib\ir\legacypassmanager.cpp, line 1703
0x00E40AD2 (0x00000005 0x04153320 0x0415D408 0x0415D4AC), `anonymous namespace'::EmitAssemblyHelper::EmitAssembly() + 0x512 bytes(s), d:\src\llvm\tools\clang\lib\codegen\backendutil.cpp, line 750 + 0x5 byte(s)
0x00E40BD1 (0x04154960 0x041506D8 0x0414C0E0 0x0414BFC8), clang::EmitBackendOutput() + 0x71 bytes(s), d:\src\llvm\tools\clang\lib\codegen\backendutil.cpp, line766
0x01E4CB8F (0x04186868 0x0413CD78 0x0414CF68 0x0413CD78), clang::BackendConsumer::HandleTranslationUnit() + 0x1AF bytes(s), d:\src\llvm\tools\clang\lib\codegen\codegenaction.cpp, line 195 + 0x3E byte(s)
0x01526DAB (0x041BB278 0x00000000 0x00000000 0x0413CD78), clang::ParseAST() + 0x22B bytes(s), d:\src\llvm\tools\clang\lib\parse\parseast.cpp, line 1700x010705EF (0x0414CF68 0x00000000 0x0413CD78 0x0413CD78), clang::ASTFrontendAction::ExecuteAction() + 0x7F bytes(s), d:\src\llvm\tools\clang\lib\frontend\frontendaction.cpp, line 558 + 0x26 byte(s)
0x01E4C737 (0x0414E894 0x0414E870 0x0414CF68 0x0104FDB9), clang::CodeGenAction::ExecuteAction() + 0x337 bytes(s), d:\src\llvm\tools\clang\lib\codegen\codegenaction.cpp, line 868
0x010704FF (0x00000000 0x0413CD78 0x00000000 0x0414CF68), clang::FrontendAction::Execute() + 0x2F bytes(s), d:\src\llvm\tools\clang\lib\frontend\frontendaction. cpp, line 463
0x0104FDB9 (0x0413CD78 0x0413A160 0x0414CF68 0x0414CF68), clang::CompilerInstance::ExecuteAction() + 0x209 bytes(s), d:\src\llvm\tools\clang\lib\frontend\compilerinstance.cpp, line 872
0x010C7928 (0x0414CF68 0x03CDF30C 0x00000000 0x03CDEFA8), clang::ExecuteCompilerInvocation() + 0x448 bytes(s), d:\src\llvm\tools\clang\lib\frontendtool\executecompilerinvocation.cpp, line 246 + 0x8 byte(s)
0x001B8338 (0x03CDEFB0 0x000000D7 0x04142F08 0x00141118), cc1_main() + 0x368 bytes(s), d:\src\llvm\tools\clang\tools\driver\cc1_main.cpp, line 116 + 0x6 byte(s)
0x001B34D7 (0x03CDEFA8 0x000000D9 0x04142F38 0x00000000), ExecuteCC1Tool() + 0x27 bytes(s), d:\src\llvm\tools\clang\tools\driver\driver.cpp, line 299 + 0x1C byte(s)
0x001B5A93 (0x000000D9 0x0413AC40 0x041394E8 0xF9F31F21), main() + 0x603 bytes(s), d:\src\llvm\tools\clang\tools\driver\driver.cpp, line 380 + 0x4A byte(s)
0x01D78504 (0x7EFDE000 0x03CDFA54 0x77A79902 0x7EFDE000), __tmainCRTStartup() + 0xFD bytes(s), f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c, line 626 + 0x17 byte(s)
0x755D338A (0x7EFDE000 0x249FBDD9 0x00000000 0x00000000), BaseThreadInitThunk() + 0x12 bytes(s)
0x77A79902 (0x01D785B2 0x7EFDE000 0x00000000 0x00000000), RtlInitializeException Chain() + 0x63 bytes(s)
0x77A798D5 (0x01D785B2 0x7EFDE000 0x00000000 0x00000000), RtlInitializeException Chain() + 0x36 bytes(s)


It's crashing here:

void X86FrameLowering::emitEpilogue(MachineFunction &MF,
                                    MachineBasicBlock &MBB) const {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
  MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
  unsigned RetOpcode = MBBI->getOpcode();    <--- CRASH


Trying to understand what Duncan's change actually did..

Duncan commited r278572 for this, let's see how it goes

Some more fixes landed in r278577 and r278587.