[llvm-bugs] [Bug 39087] New: Ternary define/macro with a dead branch is always evaluated

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39087

            Bug ID: 39087
           Summary: Ternary define/macro with a dead branch is always
                    evaluated
           Product: clang
           Version: unspecified
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: joe at benden.us
                CC: llvm-bugs at lists.llvm.org

The following sample program refuses to compile; yet works fine on other
compilers.

```
#include <arm_neon.h>

#define vroti_epi32(x, i)                                         \
        (i < 0 ? vsliq_n_u32(vshrq_n_u32(x, 32 - i), x, i)        \
               : vsriq_n_u32(vshlq_n_u32(x, 32 + i), x, -i))

int main()
{
        uint32x4_t x = vdupq_n_u32(42);
        uint32x4_t value = vroti_epi32(x, 12);

        return 0;
}
```

When compiling, the following output is shown:

```
example.c:10:21: error: argument should be a value from 0 to 31
        uint32x4_t value = vroti_epi32(x, 12);
                           ^
example.c:5:30: note: expanded from macro 'vroti_epi32'
               : vsriq_n_u32(vshlq_n_u32(x, 32 + i), x, -i))
                             ^
/usr/lib/llvm-3.6/bin/../lib/clang/3.6.0/include/arm_neon.h:23019:24: note:
expanded from macro 'vshlq_n_u32'
  __ret = (uint32x4_t) __builtin_neon_vshlq_n_v((int8x16_t)__s0, __p1, 50); \
                       ^
/usr/lib/llvm-3.6/bin/../lib/clang/3.6.0/include/arm_neon.h:24704:21: note:
expanded from macro 'vsriq_n_u32'
  uint32x4_t __s0 = __p0; \
                    ^
example.c:10:21: error: argument should be a value from 1 to 32
        uint32x4_t value = vroti_epi32(x, 12);
                           ^
example.c:5:18: note: expanded from macro 'vroti_epi32'
               : vsriq_n_u32(vshlq_n_u32(x, 32 + i), x, -i))
                 ^
/usr/lib/llvm-3.6/bin/../lib/clang/3.6.0/include/arm_neon.h:24707:24: note:
expanded from macro 'vsriq_n_u32'
  __ret = (uint32x4_t) __builtin_neon_vsriq_n_v((int8x16_t)__s0,
(int8x16_t)__s1, __p2, 50); \
                       ^
2 errors generated.
```

I expected that the program compile and execute, successfully.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180926/b883011f/attachment.html>