[CMake] Don't parse target triple except for arch

[phosek]

Summary

compiler-rt CMake build currently tries to parse the triple and then
put it back together, but doing so inherently tricky, and doing so
from CMake is just crazy and currently doesn't handle triples that
have more than three components. Fortunatelly, the CMake really only
needs the architecture part, which is typically the first component,
to construct variants for other architectures. This means we can keep
the rest of the triple as is and avoid the parsing altogether.

[phosek]

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

279

I'm not sure if COMPILER_RT_DEFAULT_TARGET_TRIPLE_SUFFIX is the best name for what this represents (triple without the arch portion) so I'm open to better suggestions if you have any.

[phosek]

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

279

I've done a bit more cleanup and this is no longer needed.

[morehouse]

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

98

Should this be begin + length - 1 since the foreach loop includes end in its range?

106

Maybe break() after the first index that's too large?

319

Do we need to implement list_sublist if this is the only use of it? Maybe removing the first element from triple_list would be simpler.

compiler-rt/CMakeLists.txt

if (COMPILER_RT_STANDALONE_BUILD)
   if (MSVC OR XCODE)
     set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
   endif()
   set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
   set(LLVM_LIT_OUTPUT_DIR "${COMPILER_RT_EXEC_OUTPUT_DIR}")
 endif()
 
 construct_compiler_rt_default_triple()
-if ("${COMPILER_RT_DEFAULT_TARGET_ABI}" MATCHES "hf$")
+if ("${COMPILER_RT_DEFAULT_TARGET_TRIPLE}" MATCHES ".*hf$")
   if (${COMPILER_RT_DEFAULT_TARGET_ARCH} MATCHES "^arm")
     set(COMPILER_RT_DEFAULT_TARGET_ARCH "armhf")
   endif()
 endif()
-if ("${COMPILER_RT_DEFAULT_TARGET_ABI}" MATCHES "^android")
+if ("${COMPILER_RT_DEFAULT_TARGET_TRIPLE}" MATCHES ".*android.*")
   set(ANDROID 1)
 endif()
 pythonize_bool(ANDROID)
 
 set(COMPILER_RT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(COMPILER_RT_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 pythonize_bool(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

 
 # Takes ${ARGN} and puts only supported architectures in @out_var list.
 function(filter_available_targets out_var)
   set(archs ${${out_var}})
   foreach(arch ${ARGN})
     list(FIND COMPILER_RT_SUPPORTED_ARCH ${arch} ARCH_INDEX)
     if(NOT (ARCH_INDEX EQUAL -1) AND CAN_TARGET_${arch})
       list(APPEND archs ${arch})
     endif()
   endforeach()
   set(${out_var} ${archs} PARENT_SCOPE)
 endfunction()
 
 # Add $arch as supported with no additional flags.
 macro(add_default_target_arch arch)
   set(TARGET_${arch}_CFLAGS "")
   set(CAN_TARGET_${arch} 1)
   list(APPEND COMPILER_RT_SUPPORTED_ARCH ${arch})
 endmacro()
 
 function(check_compile_definition def argstring out_var)
   if("${def}" STREQUAL "")
     set(${out_var} TRUE PARENT_SCOPE)
     return()
   endif()
macro(construct_compiler_rt_default_triple)
   if(DEFINED COMPILER_RT_TEST_TARGET_TRIPLE)
     # Backwards compatibility: this variable used to be called
     # COMPILER_RT_TEST_TARGET_TRIPLE.
     set(COMPILER_RT_DEFAULT_TARGET_TRIPLE ${COMPILER_RT_TEST_TARGET_TRIPLE})
   endif()
 
   string(REPLACE "-" ";" TARGET_TRIPLE_LIST ${COMPILER_RT_DEFAULT_TARGET_TRIPLE})
   list(GET TARGET_TRIPLE_LIST 0 COMPILER_RT_DEFAULT_TARGET_ARCH)
-  list(GET TARGET_TRIPLE_LIST 1 COMPILER_RT_DEFAULT_TARGET_OS)
-  list(LENGTH TARGET_TRIPLE_LIST TARGET_TRIPLE_LIST_LENGTH)
-  if(TARGET_TRIPLE_LIST_LENGTH GREATER 2)
-    list(GET TARGET_TRIPLE_LIST 2 COMPILER_RT_DEFAULT_TARGET_ABI)
-  endif()
   # Determine if test target triple is specified explicitly, and doesn't match the
   # default.
   if(NOT COMPILER_RT_DEFAULT_TARGET_TRIPLE STREQUAL TARGET_TRIPLE)
     set(COMPILER_RT_HAS_EXPLICIT_DEFAULT_TARGET_TRIPLE TRUE)
   else()
     set(COMPILER_RT_HAS_EXPLICIT_DEFAULT_TARGET_TRIPLE FALSE)
   endif()
 endmacro()
 
elseif(${_file} MATCHES ".*/.*\\.S" OR ${_file} MATCHES ".*/.*\\.c")
       string(REPLACE ".S" ".c" _cname "${_name}")
       list(REMOVE_ITEM intermediate ${_cname})
     endif ()
   endforeach ()
   set(${output_var} ${intermediate} PARENT_SCOPE)
 endfunction()
 
 function(get_compiler_rt_target arch variable)
+  string(FIND ${COMPILER_RT_DEFAULT_TARGET_TRIPLE} "-" dash_index)
+  string(SUBSTRING ${COMPILER_RT_DEFAULT_TARGET_TRIPLE} ${dash_index} -1 triple_suffix)
   if(ANDROID AND ${arch} STREQUAL "i386")
-    set(target "i686${COMPILER_RT_OS_SUFFIX}-${COMPILER_RT_DEFAULT_TARGET_OS}")
+    set(target "i686${COMPILER_RT_OS_SUFFIX}${triple_suffix}")
   else()
-    set(target "${arch}-${COMPILER_RT_DEFAULT_TARGET_OS}")
-  endif()
-  if(COMPILER_RT_DEFAULT_TARGET_ABI)
-    set(target "${target}-${COMPILER_RT_DEFAULT_TARGET_ABI}")
+    set(target "${arch}${triple_suffix}")
   endif()
   set(${variable} ${target} PARENT_SCOPE)
 endfunction()
 
 function(get_compiler_rt_install_dir arch install_dir)
   if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
     get_compiler_rt_target(${arch} target)
     set(${install_dir} ${COMPILER_RT_INSTALL_PATH}/${target}/lib PARENT_SCOPE)