[llvm] RuntimeLibcalls: Add bitset for available libcalls (PR #150869)

[Sergei Barannikov via llvm-commits]

================
@@ -616,6 +618,21 @@ else ()
   endif ()
 endif ()
 
+foreach(i IN ITEMS 8 4)
+  try_compile(SIZEOF_UINTPTR_T_IS_${i}
+    SOURCE_FROM_CONTENT
+    "test-sizeof-uintptr_t.cpp"
+    "#include <cstdint>\n
+     static_assert(sizeof(uintptr_t) == ${i}); int main(){}"
+    CXX_STANDARD 17
+    LOG_DESCRIPTION "testing sizeof(uintptr_t)")
+
+  if(SIZEOF_UINTPTR_T_IS_${i})
+    set(LLVM_NATIVE_ARCH_SIZEOF_UINTPTR_T ${i})
+    break()
+  endif()
+endforeach()
----------------
s-barannikov wrote:

I get the correct value when using x32 ABI:
```cmake
cmake_minimum_required(VERSION 3.25)
project(test LANGUAGES C CXX)
message(STATUS "CMAKE_SIZEOF_VOID_P = ${CMAKE_SIZEOF_VOID_P}")
```
```shell
$ cmake . -DCMAKE_CXX_FLAGS="-mx32"
-- The C compiler identification is GNU 13.3.0
-- The CXX compiler identification is GNU 13.3.0
...
-- CMAKE_SIZEOF_VOID_P = 4
```

Internally, it does the same try_compile thing to get the size, except that it checks the size of `void *` instead of `uintptr_t`. I think they should be the same, but checking for uintptr_t size explicitly should be safer.




https://github.com/llvm/llvm-project/pull/150869