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

for device simulators

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.

Differential Revision: https://reviews.llvm.org/D84564

clang/lib/Driver/ToolChains/Darwin.cpp

@@ -1062,10 +1062,9 @@ void MachO::AddLinkRuntimeLib(const ArgList &Args, ArgStringList &CmdArgs,
     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(

clang/test/Driver/darwin-ld.c

@@ -156,7 +156,7 @@
 // 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

compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake

@@ -289,6 +289,15 @@ macro(darwin_add_builtin_library name suffix)
     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}
@@ -449,16 +458,13 @@ macro(darwin_add_builtin_libraries)
     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 ${COMPILER_RT_LIBRARY_INSTALL_DIR})
-    endif()
+    darwin_lipo_libs(clang_rt.${os}
+                     PARENT_TARGET builtins
+                     LIPO_FLAGS ${${os}_builtins_lipo_flags}
+                     DEPENDS ${${os}_builtins_libs}
+                     OUTPUT_DIR ${COMPILER_RT_LIBRARY_OUTPUT_DIR}
+                     INSTALL_DIR ${COMPILER_RT_LIBRARY_INSTALL_DIR})
   endforeach()
   darwin_add_embedded_builtin_libraries()
 endmacro()