Revert "[LSV] Refactoring + supporting bitcasts to a type of different size"

Revert "[LSV] Refactoring + supporting bitcasts to a type of different size"

This reverts commit r337489.
It causes asserts to fire in some TensorFlow tests, e.g.
tensorflow/compiler/tests/gather_test.py on GPU.

Example stack trace:
Start test case: GatherTest.testHigherRank
assertion failed at third_party/llvm/llvm/lib/Support/APInt.cpp:819 in llvm::APInt llvm::APInt::trunc(unsigned int) const: width && "Can't truncate to 0 bits"
    @     0x5559446ebe10  __assert_fail
    @     0x55593ef32f5e  llvm::APInt::trunc()
    @     0x55593d78f86e  (anonymous namespace)::Vectorizer::lookThroughComplexAddresses()
    @     0x55593d78f2bc  (anonymous namespace)::Vectorizer::areConsecutivePointers()
    @     0x55593d78d128  (anonymous namespace)::Vectorizer::isConsecutiveAccess()
    @     0x55593d78c926  (anonymous namespace)::Vectorizer::vectorizeInstructions()
    @     0x55593d78c221  (anonymous namespace)::Vectorizer::vectorizeChains()
    @     0x55593d78b948  (anonymous namespace)::Vectorizer::run()
    @     0x55593d78b725  (anonymous namespace)::LoadStoreVectorizer::runOnFunction()
    @     0x55593edf4b17  llvm::FPPassManager::runOnFunction()
    @     0x55593edf4e55  llvm::FPPassManager::runOnModule()
    @     0x55593edf563c  (anonymous namespace)::MPPassManager::runOnModule()
    @     0x55593edf5137  llvm::legacy::PassManagerImpl::run()
    @     0x55593edf5b71  llvm::legacy::PassManager::run()
    @     0x55593ced250d  xla::gpu::IrDumpingPassManager::run()
    @     0x55593ced5033  xla::gpu::(anonymous namespace)::EmitModuleToPTX()
    @     0x55593ced40ba  xla::gpu::(anonymous namespace)::CompileModuleToPtx()
    @     0x55593ced33d0  xla::gpu::CompileToPtx()
    @     0x55593b26b2a2  xla::gpu::NVPTXCompiler::RunBackend()
    @     0x55593b21f973  xla::Service::BuildExecutable()
    @     0x555938f44e64  xla::LocalService::CompileExecutable()
    @     0x555938f30a85  xla::LocalClient::Compile()
    @     0x555938de3c29  tensorflow::XlaCompilationCache::BuildExecutable()
    @     0x555938de4e9e  tensorflow::XlaCompilationCache::CompileImpl()
    @     0x555938de3da5  tensorflow::XlaCompilationCache::Compile()
    @     0x555938c5d962  tensorflow::XlaLocalLaunchBase::Compute()
    @     0x555938c68151  tensorflow::XlaDevice::Compute()
    @     0x55593f389e1f  tensorflow::(anonymous namespace)::ExecutorState::Process()
    @     0x55593f38a625  tensorflow::(anonymous namespace)::ExecutorState::ScheduleReady()::$_1::operator()()
*** SIGABRT received by PID 7798 (TID 7837) from PID 7798; ***

llvm-svn: 337541