[llvm-bugs] [Bug 38923] New: _mm_insert_epi16 passes int to signature taking short

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38923

            Bug ID: 38923
           Summary: _mm_insert_epi16 passes int to signature taking short
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: steveire at gmail.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

Given 

    $ type ..\simplemain.cpp
    #include <intrin.h>

    int main(int argc, char**)
    {
        __m128i mask = _mm_insert_epi16(__m128i{}, 0x8000, 0x1);

        return 0;
    }

I get:

    $ "C:\\dev\\src\\llvm\\build\\releaseprefix\\bin\\clang.exe" -cc1 -I
"C:\\dev\\src\\llvm\\build\\releaseprefix\\lib\\clang\\8.0.0\\include"
-internal-isystem "C:\\Program Files (x86)\\Microsoft Visual
Studio\\Preview\\Enterprise\\VC\\Tools\\MSVC\\14.15.26726\\include"
-internal-isystem "C:\\Program Files (x86)\\Windows
Kits\\10\\Include\\10.0.17134.0\\ucrt" -fms-compatibility
-fms-compatibility-version=19.15 -x c++ "..\\simplemain.cpp"

    ..\\simplemain.cpp:5:20: warning: implicit conversion from 'int' to 'short'
changes value from 32768 to -32768
        __m128i mask = _mm_insert_epi16(__m128i{}, 0x8000, 0x1);
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   
C:\\dev\\src\\llvm\\build\\releaseprefix\\lib\\clang\\8.0.0\\include\emmintrin.h:4297:62:
note: expanded from macro '_mm_insert_epi16'
      (__m128i)__builtin_ia32_vec_set_v8hi((__v8hi)(__m128i)(a), (int)(b), \
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~                       ^~~~~~~~
    1 warning generated.


This warning gets emitted a lot when using clang-tidy, which invokes the
compiler directly. I can silence it by using `-isystem`, but the warning seems
to be legitimate. `_mm_insert_epi16` accepts an integer and casts it to `int`
in the call to `__builtin_ia32_vec_set_v8hi`, but `__builtin_ia32_vec_set_v8hi`
takes a short at that position.

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