r192143 - Suppress useless -Wshadow warning when using _mm* macros from emmintrin.h

[Bob Wilson]

On Oct 7, 2013, at 5:19 PM, Ted Kremenek <kremenek at apple.com> wrote:

> Interesting.  Yes that seems like a reasonably generic heuristic.  It does get potentially complicated if a macro uses another macro though… conceptually all from the same “expansion”.

emmintrin.h is just one case.  Many of the ARM Neon intrinsics have this same issue.  I suppose we could use the same _Pragma approach for those, but a more general solution would be nice.

> 
> On Oct 7, 2013, at 5:11 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> 
>> Maybe we should teach Clang not to warn on shadowing if the declaration and all its uses come from the same macro expansion?
>> 
>> 
>> On Mon, Oct 7, 2013 at 4:51 PM, Ted Kremenek <kremenek at apple.com> wrote:
>> Author: kremenek
>> Date: Mon Oct  7 18:51:11 2013
>> New Revision: 192143
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=192143&view=rev
>> Log:
>> Suppress useless -Wshadow warning when using _mm* macros from emmintrin.h
>> 
>> Fixes <rdar://problem/10679282>.
>> 
>> I'm not completely satisfied with this patch.  Sprinkling "diagnostic ignored"
>> _Pragmas throughout this file is gross, but I couldn't suppress
>> it for the entire file.
>> 
>> Modified:
>>     cfe/trunk/lib/Headers/emmintrin.h
>>     cfe/trunk/test/Sema/warn-shadow.c
>> 
>> Modified: cfe/trunk/lib/Headers/emmintrin.h
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Headers/emmintrin.h?rev=192143&r1=192142&r2=192143&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Headers/emmintrin.h (original)
>> +++ cfe/trunk/lib/Headers/emmintrin.h Mon Oct  7 18:51:11 2013
>> @@ -826,7 +826,9 @@ _mm_xor_si128(__m128i __a, __m128i __b)
>>  }
>> 
>>  #define _mm_slli_si128(a, count) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128i __a = (a); \
>> +   _Pragma("clang diagnostic pop"); \
>>    (__m128i)__builtin_ia32_pslldqi128(__a, (count)*8); })
>> 
>>  static __inline__ __m128i __attribute__((__always_inline__, __nodebug__))
>> @@ -891,7 +893,9 @@ _mm_sra_epi32(__m128i __a, __m128i __cou
>> 
>> 
>>  #define _mm_srli_si128(a, count) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128i __a = (a); \
>> +  _Pragma("clang diagnostic pop"); \
>>    (__m128i)__builtin_ia32_psrldqi128(__a, (count)*8); })
>> 
>>  static __inline__ __m128i __attribute__((__always_inline__, __nodebug__))
>> @@ -1280,20 +1284,26 @@ _mm_movemask_epi8(__m128i __a)
>>  }
>> 
>>  #define _mm_shuffle_epi32(a, imm) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128i __a = (a); \
>> +  _Pragma("clang diagnostic pop"); \
>>    (__m128i)__builtin_shufflevector((__v4si)__a, (__v4si) _mm_set1_epi32(0), \
>>                                     (imm) & 0x3, ((imm) & 0xc) >> 2, \
>>                                     ((imm) & 0x30) >> 4, ((imm) & 0xc0) >> 6); })
>> 
>>  #define _mm_shufflelo_epi16(a, imm) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128i __a = (a); \
>> +  _Pragma("clang diagnostic pop"); \
>>    (__m128i)__builtin_shufflevector((__v8hi)__a, (__v8hi) _mm_set1_epi16(0), \
>>                                     (imm) & 0x3, ((imm) & 0xc) >> 2, \
>>                                     ((imm) & 0x30) >> 4, ((imm) & 0xc0) >> 6, \
>>                                     4, 5, 6, 7); })
>> 
>>  #define _mm_shufflehi_epi16(a, imm) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128i __a = (a); \
>> +  _Pragma("clang diagnostic pop"); \
>>    (__m128i)__builtin_shufflevector((__v8hi)__a, (__v8hi) _mm_set1_epi16(0), \
>>                                     0, 1, 2, 3, \
>>                                     4 + (((imm) & 0x03) >> 0), \
>> @@ -1386,8 +1396,10 @@ _mm_movemask_pd(__m128d __a)
>>  }
>> 
>>  #define _mm_shuffle_pd(a, b, i) __extension__ ({ \
>> +  _Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wshadow\""); \
>>    __m128d __a = (a); \
>>    __m128d __b = (b); \
>> +  _Pragma("clang diagnostic pop"); \
>>    __builtin_shufflevector(__a, __b, (i) & 1, (((i) & 2) >> 1) + 2); })
>> 
>>  static __inline__ __m128 __attribute__((__always_inline__, __nodebug__))
>> 
>> Modified: cfe/trunk/test/Sema/warn-shadow.c
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-shadow.c?rev=192143&r1=192142&r2=192143&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/Sema/warn-shadow.c (original)
>> +++ cfe/trunk/test/Sema/warn-shadow.c Mon Oct  7 18:51:11 2013
>> @@ -1,5 +1,7 @@
>>  // RUN: %clang_cc1 -verify -fsyntax-only -fblocks -Wshadow %s
>> 
>> +#include <emmintrin.h>
>> +
>>  int i;          // expected-note 3 {{previous declaration is here}}
>> 
>>  void foo() {
>> @@ -59,3 +61,11 @@ void rdar8883302() {
>>  void test8() {
>>    int bob; // expected-warning {{declaration shadows a variable in the global scope}}
>>  }
>> +
>> +// Test that using two macros from emmintrin do not cause a
>> +// useless -Wshadow warning.
>> +void rdar10679282() {
>> +  __m128i qf = _mm_setzero_si128();
>> +  qf = _mm_slli_si128(_mm_add_epi64(qf, _mm_srli_si128(qf, 8)), 8); // no-warning
>> +  (void) qf;
>> +}
>> 
>> 
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> 
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