[llvm-bugs] [Bug 37870] New: __builtin_shuffle parsing bug

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37870

            Bug ID: 37870
           Summary: __builtin_shuffle parsing bug
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: zhonghao at pku.org.cn
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

The code is as follow:

typedef int V __attribute__((vector_size (16)));
V a, b, c;

int
foo ()
{
 return __builtin_shuffle (a, b, c)[3];
}

int
main ()
{
 a = (V) { 1, 2, 3, 4 };
 b = (V) { 5, 6, 7, 8 };
 c = (V) { 7, 2, 5, 6 };
 if (foo () != 7)
 __builtin_abort ();
 return 0;
}

clang++ rejects the code with an error message:

error: use of undeclared identifier '__builtin_shuffle'
     return __builtin_shuffle (a, b, c)[3];
            ^
    1 error generated.

The code comes from a gcc bug report:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78089

 Jakub Jelinek explained why it is a bug.

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