r180909 - Only evaluate __has_feature(c_thread_local) and __has_feature(cxx_thread_local) true when the target supports thread-local storage.

[Douglas Gregor]

On May 2, 2013, at 1:00 AM, Jean-Daniel Dupas <devlists at shadowlab.org> wrote:

> Is it OK to use the same condition for both while they don't require the same Target support ? 
> 
> AFAK, C++ TLS require __cxa_thread_atexit support, and so the target should support thread_atexit, while C TLS doesn't need it.

As Richard notes, whether __cxa_thread_atexit is available or not is a library issue, and we don't have visibility into that within the frontend. However, we do know whether the target supports thread-local storage in general (it's part of target information), and my change makes __has_feature(c(xx)?_thread_local) match what Sema actually allows.

> Actually, I think darwin has support for C thread local, but no C++ thread local.

x86 Darwin fully supports thread-local, although the __cxa_thread_atexit equivalent is called __tlv_atexit. ARM Darwin does not support thread-local (at all).

	- Doug


> Le 2 mai 2013 à 07:28, Douglas Gregor <dgregor at apple.com> a écrit :
> 
>> Author: dgregor
>> Date: Thu May  2 00:28:32 2013
>> New Revision: 180909
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=180909&view=rev
>> Log:
>> Only evaluate __has_feature(c_thread_local) and __has_feature(cxx_thread_local) true when the target supports thread-local storage.
>> 
>> Modified:
>>   cfe/trunk/lib/Lex/PPMacroExpansion.cpp
>>   cfe/trunk/test/Lexer/has_feature_cxx0x.cpp
>> 
>> Modified: cfe/trunk/lib/Lex/PPMacroExpansion.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/PPMacroExpansion.cpp?rev=180909&r1=180908&r2=180909&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Lex/PPMacroExpansion.cpp (original)
>> +++ cfe/trunk/lib/Lex/PPMacroExpansion.cpp Thu May  2 00:28:32 2013
>> @@ -751,7 +751,8 @@ static bool HasFeature(const Preprocesso
>>           .Case("c_atomic", LangOpts.C11)
>>           .Case("c_generic_selections", LangOpts.C11)
>>           .Case("c_static_assert", LangOpts.C11)
>> -           .Case("c_thread_local", LangOpts.C11)
>> +           .Case("c_thread_local", 
>> +                 LangOpts.C11 && PP.getTargetInfo().isTLSSupported())
>>           // C++11 features
>>           .Case("cxx_access_control_sfinae", LangOpts.CPlusPlus11)
>>           .Case("cxx_alias_templates", LangOpts.CPlusPlus11)
>> @@ -783,7 +784,8 @@ static bool HasFeature(const Preprocesso
>>           .Case("cxx_rvalue_references", LangOpts.CPlusPlus11)
>>           .Case("cxx_strong_enums", LangOpts.CPlusPlus11)
>>           .Case("cxx_static_assert", LangOpts.CPlusPlus11)
>> -           .Case("cxx_thread_local", LangOpts.CPlusPlus11)
>> +           .Case("cxx_thread_local", 
>> +                 LangOpts.CPlusPlus11 && PP.getTargetInfo().isTLSSupported())
>>           .Case("cxx_trailing_return", LangOpts.CPlusPlus11)
>>           .Case("cxx_unicode_literals", LangOpts.CPlusPlus11)
>>           .Case("cxx_unrestricted_unions", LangOpts.CPlusPlus11)
>> 
>> Modified: cfe/trunk/test/Lexer/has_feature_cxx0x.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Lexer/has_feature_cxx0x.cpp?rev=180909&r1=180908&r2=180909&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/Lexer/has_feature_cxx0x.cpp (original)
>> +++ cfe/trunk/test/Lexer/has_feature_cxx0x.cpp Thu May  2 00:28:32 2013
>> @@ -1,5 +1,6 @@
>> -// RUN: %clang_cc1 -E -std=c++11 %s -o - | FileCheck --check-prefix=CHECK-0X %s
>> -// RUN: %clang_cc1 -E %s -o - | FileCheck --check-prefix=CHECK-NO-0X %s
>> +// RUN: %clang_cc1 -E -triple x86_64-linux-gnu -std=c++11 %s -o - | FileCheck --check-prefix=CHECK-0X %s
>> +// RUN: %clang_cc1 -E -triple armv7-apple-darwin -std=c++11 %s -o - | FileCheck --check-prefix=CHECK-NO-TLS %s
>> +// RUN: %clang_cc1 -E -triple x86_64-linux-gnu %s -o - | FileCheck --check-prefix=CHECK-NO-0X %s
>> 
>> #if __has_feature(cxx_atomic)
>> int has_atomic();
>> @@ -290,3 +291,4 @@ int no_thread_local();
>> 
>> // CHECK-0X: has_thread_local
>> // CHECK-NO-0X: no_thread_local
>> +// CHECK-NO-TLS: no_thread_local
>> 
>> 
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> 
> -- Jean-Daniel
> 
> 
> 
>