[AMDGPU] Re-Re-apply: Implement vop3p complex pattern optmization for gisel

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

@@ -4563,6 +4563,7 @@ static SrcStatus getNegStatus(Register Reg, SrcStatus S,
   default:
     llvm_unreachable("unexpected SrcStatus");
   }
+  llvm_unreachable("unexpected SrcStatus");
 }
 
 static std::optional<std::pair<Register, SrcStatus>>

llvm/test/lit.cfg.py

@@ -474,7 +474,7 @@ def have_cxx_shared_library():
         print("could not exec llvm-readobj")
         return False
 
-    readobj_out = readobj_cmd.stdout.read().decode("ascii")
+    readobj_out = readobj_cmd.stdout.read().decode("utf-8")
     readobj_cmd.wait()
 
     regex = re.compile(r"(libc\+\+|libstdc\+\+|msvcp).*\.(so|dylib|dll)")