[darwin] build and link with a separate compiler-rt builtins library for device simulators

[arphaman]

Summary

This change separates out the iOS/tvOS/watchOS simulator slices from the "libclang_rt.<os>.a" fat archive, by moving them out to their own "libclang_rt.<os>sim.a" static archive.
This allows us to build and to link with an arm64 device simulator slice for the simulators running on Apple Silicons, and to distribute it in one archive alongside the Intel simulator slices.

[steven_wu]

LGTM

clang/lib/Driver/ToolChains/Darwin.cpp

void MachO::AddLinkRuntimeLib(const ArgList &Args, ArgStringList &CmdArgs,
                               StringRef Component, RuntimeLinkOptions Opts,
                               bool IsShared) const {
   SmallString<64> DarwinLibName = StringRef("libclang_rt.");
   // an Darwin the builtins compomnent is not in the library name
   if (Component != "builtins") {
     DarwinLibName += Component;
     if (!(Opts & RLO_IsEmbedded))
       DarwinLibName += "_";
-    DarwinLibName += getOSLibraryNameSuffix();
-  } else
-    DarwinLibName += getOSLibraryNameSuffix(true);
+  }
 
+  DarwinLibName += getOSLibraryNameSuffix();
   DarwinLibName += IsShared ? "_dynamic.dylib" : ".a";
   SmallString<128> Dir(getDriver().ResourceDir);
   llvm::sys::path::append(
       Dir, "lib", (Opts & RLO_IsEmbedded) ? "macho_embedded" : "darwin");
 
   SmallString<128> P(Dir);
   llvm::sys::path::append(P, DarwinLibName);
 

clang/test/Driver/darwin-ld.c

 // RUN: %clang -target arm64-apple-ios5.0 -miphoneos-version-min=5.0 -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=LINK_NO_IOS_ARM64_CRT1 %s < %t.log
 // LINK_NO_IOS_ARM64_CRT1-NOT: crt
 
 // RUN: %clang -target x86_64-apple-ios6.0 -miphoneos-version-min=6.0 -fprofile-instr-generate -resource-dir=%S/Inputs/resource_dir -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=LINK_IOSSIM_PROFILE %s < %t.log
 // LINK_IOSSIM_PROFILE: {{ld(.exe)?"}}
 // LINK_IOSSIM_PROFILE: libclang_rt.profile_iossim.a
-// LINK_IOSSIM_PROFILE: libclang_rt.ios.a
+// LINK_IOSSIM_PROFILE: libclang_rt.iossim.a
 
 // RUN: %clang -target arm64-apple-tvos8.3 -mlinker-version=400 -mtvos-version-min=8.3 -resource-dir=%S/Inputs/resource_dir -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=LINK_TVOS_ARM64 %s < %t.log
 // LINK_TVOS_ARM64: {{ld(.exe)?"}}
 // LINK_TVOS_ARM64: -tvos_version_min
 // LINK_TVOS_ARM64-NOT: crt
 // LINK_TVOS_ARM64-NOT: lgcc_s.1
 // LINK_TVOS_ARM64: libclang_rt.tvos.a

compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake

macro(darwin_add_builtin_library name suffix)
   if("${LIB_ARCH}" MATCHES "^(armv7|armv7k|armv7s)$")
     set(builtin_cflags "")
     foreach(cflag "${LIB_CFLAGS}")
       string(REPLACE "-fomit-frame-pointer" "" cflag "${cflag}")
       list(APPEND builtin_cflags ${cflag})
     endforeach(cflag)
   endif()
 
+  if ("${LIB_OS}" MATCHES ".*sim$")
+    # Pass an explicit -simulator environment to the -target option to ensure
+    # that we don't rely on the architecture to infer whether we're building
+    # for the simulator.
+    string(REGEX REPLACE "sim" "" base_os "${LIB_OS}")
+    list(APPEND builtin_cflags
+         -target "${LIB_ARCH}-apple-${base_os}${DARWIN_${LIBOS}_BUILTIN_MIN_VER}-simulator")
+  endif()
+
   set_target_compile_flags(${libname}
     ${sysroot_flag}
     ${DARWIN_${LIB_OS}_BUILTIN_MIN_VER_FLAG}
     ${builtin_cflags})
   target_include_directories(${libname}
     PRIVATE ${LIB_INCLUDE_DIRS})
   set_property(TARGET ${libname} APPEND PROPERTY
       COMPILE_DEFINITIONS ${LIB_DEFS})
if(NOT DARWIN_${os}_SKIP_CC_KEXT)
                       PARENT_TARGET builtins
                       LIPO_FLAGS ${${os}_cc_kext_lipo_flags}
                       DEPENDS ${${os}_cc_kext_libs}
                       OUTPUT_DIR ${COMPILER_RT_LIBRARY_OUTPUT_DIR}
                       INSTALL_DIR ${COMPILER_RT_LIBRARY_INSTALL_DIR})
     endif()
   endforeach()
 
-  # We put the x86 sim slices into the archives for their base OS
   foreach (os ${ARGN})
-    if(NOT ${os} MATCHES ".*sim$")
-      darwin_lipo_libs(clang_rt.${os}
-                        PARENT_TARGET builtins
-                        LIPO_FLAGS ${${os}_builtins_lipo_flags} ${${os}sim_builtins_lipo_flags}
-                        DEPENDS ${${os}_builtins_libs} ${${os}sim_builtins_libs}
-                        OUTPUT_DIR ${COMPILER_RT_LIBRARY_OUTPUT_DIR}
-                        INSTALL_DIR ${COMPILER_RT_LIBRARY_INSTALL_DIR})
-    endif()
+                     LIPO_FLAGS ${${os}_builtins_lipo_flags}
+                     DEPENDS ${${os}_builtins_libs}
   endforeach()
   darwin_add_embedded_builtin_libraries()
 endmacro()
 
 macro(darwin_add_embedded_builtin_libraries)
   # this is a hacky opt-out. If you can't target both intel and arm
   # architectures we bail here.
   set(DARWIN_SOFT_FLOAT_ARCHS armv6m armv7m armv7em armv7)