Add predefined macro __gnu_linux__ for proper aux-triple

[yaxunl]

Summary

Clang predefine macro __linx__ for aux-triple with Linux OS
but does not predefine macro __gnu_linux__. This causes
some compilation error for certain applications, e.g. Eigen.

This patch fixes that.

[tra]

lib/Frontend/InitPreprocessor.cpp

1126

AFAICT, we always define __gnu_linix__ on Linux:
https://github.com/llvm-mirror/clang/blob/master/lib/Basic/Targets/OSTargets.h#L306

I think it should be the case here, too.

[yaxunl]

Revised by Artem's comments.

[tra]

While we're here, perhaps Builder.defineMacro("__linux__") should be changed to DefineStd("linux") which defines linux/__linux/__linux__?

[yaxunl]

In D51441#1218010, @tra wrote:

While we're here, perhaps Builder.defineMacro("__linux__") should be changed to DefineStd("linux") which defines linux/__linux/__linux__?

Will do when committing. Thanks.

[yaxunl]

In D51441#1218034, @yaxunl wrote:

In D51441#1218010, @tra wrote:

While we're here, perhaps Builder.defineMacro("__linux__") should be changed to DefineStd("linux") which defines linux/__linux/__linux__?

Will do when committing. Thanks.

Sorry DefineStd is a function not available in InitPreprocessor.cpp. To reuse that function refactoring is required, which is out of scope for this patch.

[tra]

Reverted in rL341115.

[tra]

Tests reverted in rL341118.

lib/Frontend/InitPreprocessor.cpp

   default:
     break;
   }
 
   // libc++ needs to find out the object file format and threading API.
   if (AuxTriple.getOS() == llvm::Triple::Linux) {
     Builder.defineMacro("__ELF__");
     Builder.defineMacro("__linux__");
+    Builder.defineMacro("__gnu_linux__");
     // Used in features.h. If this is omitted, math.h doesn't declare float
     // versions of the functions in bits/mathcalls.h.
     if (LangOpts.CPlusPlus)
       Builder.defineMacro("_GNU_SOURCE");
   } else if (AuxTriple.isOSDarwin()) {
     Builder.defineMacro("__APPLE__");
     Builder.defineMacro("__MACH__");
   } else if (AuxTriple.isOSWindows()) {

test/Preprocessor/predefined-macros.c

 // RUN: %clang_cc1 %s -E -dM -o - -x hip -triple amdgcn-amd-amdhsa \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-HIP
 // CHECK-HIP-NOT: #define __CUDA_ARCH__
 // CHECK-HIP: #define __HIPCC__ 1
 // CHECK-HIP-NOT: #define __HIP_DEVICE_COMPILE__ 1
 // CHECK-HIP: #define __HIP__ 1
 
 // RUN: %clang_cc1 %s -E -dM -o - -x hip -triple amdgcn-amd-amdhsa \
-// RUN:   -fcuda-is-device \
+// RUN:   -aux-triple x86_64-unknown-linux -fcuda-is-device \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-HIP-DEV
 // CHECK-HIP-DEV-NOT: #define __CUDA_ARCH__
 // CHECK-HIP-DEV: #define __HIPCC__ 1
 // CHECK-HIP-DEV: #define __HIP_DEVICE_COMPILE__ 1
 // CHECK-HIP-DEV: #define __HIP__ 1
+// CHECK_HIP-DEV: #define __linux__ 1
+// CHECK_HIP-DEV: #define __gnu_linux__ 1