Revert "R600: Remove softPromoteHalfType (#177420)"
This reverts commit 99fab0106b428676c37154821d955797fe1786a3.
llc was crashing in kernel-args.ll after this patch:
```
.---command stderr------------
| LLVM ERROR: Cannot select: t3: f32,ch = load<(non-temporal dereferenceable invariant load (s16), align 4, addrspace 7), sext from f16> t0, Constant:i32<36>, undef:i32
| In function: f16_arg
| PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
| Stack dump:
| 0. Program arguments: /b/ml-opt-devrel-x86-64-b1/build/bin/llc -mtriple=r600 -mcpu=redwood
| 1. Running pass 'Function Pass Manager' on module '<stdin>'.
| 2. Running pass 'Unnamed pass: implement Pass::getPassName()' on function '@f16_arg'
| #0 0x0000561402607438 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x81a7438)
| #1 0x0000561402604b75 llvm::sys::RunSignalHandlers() (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x81a4b75)
| #2 0x00005614026081b1 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
| #3 0x00007f55eb45a050 (/lib/x86_64-linux-gnu/libc.so.6+0x3c050)
| #4 0x00007f55eb4a8eec (/lib/x86_64-linux-gnu/libc.so.6+0x8aeec)
| #5 0x00007f55eb459fb2 raise (/lib/x86_64-linux-gnu/libc.so.6+0x3bfb2)
| #6 0x00007f55eb444472 abort (/lib/x86_64-linux-gnu/libc.so.6+0x26472)
| #7 0x0000561402567005 llvm::report_fatal_error(llvm::Twine const&, bool) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x8107005)
| #8 0x00005614023e7ba7 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f87ba7)
| #9 0x00005614023e6a7d llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f86a7d)
| #10 0x00005614023dae94 llvm::SelectionDAGISel::DoInstructionSelection() (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f7ae94)
| #11 0x00005614023d9e6a llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f79e6a)
| #12 0x00005614023d7b5e llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f77b5e)
| #13 0x00005614023d4c30 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f74c30)
| #14 0x00005614023d22e0 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7f722e0)
| #15 0x0000561401611793 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x71b1793)
| #16 0x0000561401b790e5 llvm::FPPassManager::runOnFunction(llvm::Function&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x77190e5)
| #17 0x0000561401b80f72 llvm::FPPassManager::runOnModule(llvm::Module&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7720f72)
| #18 0x0000561401b79b56 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x7719b56)
| #19 0x00005613ff4858f4 compileModule(char**, llvm::SmallVectorImpl<llvm::PassPlugin>&, llvm::LLVMContext&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&) llc.cpp:0:0
| #20 0x00005613ff482ed3 main (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x5022ed3)
| #21 0x00007f55eb44524a (/lib/x86_64-linux-gnu/libc.so.6+0x2724a)
| #22 0x00007f55eb445305 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x27305)
| #23 0x00005613ff47ea21 _start (/b/ml-opt-devrel-x86-64-b1/build/bin/llc+0x501ea21)
`-----------------------------
```
