Change llvm call once check for building Swift for PowerPC(ppc64le)

[sarveshtamba]

Summary

These changes are required to resolve the call_once related errors seen while building the Swift toolchain on PowerPC64LE. The existing macro checks are inadequate while building Swift on PowerPC64LE.

[sarveshtamba]

@nemanjai, please review and let me know if this looks good.

[sarveshtamba]

@nemanjai, any updates on this one?

[compnerd]

Did we not address the PPC related checks earlier? IIRC, the problem was that gcc does not define __PPC__ but does define __ppc__. The problem with std::call_once was not related to endian, so why not extend the condition on L32 to include __PPC__?

[sarveshtamba]

Extending the condition to include PPC

[sarveshtamba]

Hi @compnerd

In https://reviews.llvm.org/D55503, we had extended the condition to include PPC.
However, the check required to build LLVM on PPC64LE was missed in SVN r348970.

Hence as requested by @nemanjai in review request D55503, I have raised this new review request D56382. I have also extended the condition to include PPC by submitting an additional diff to this new review request D56382.

[sarveshtamba]

Hello, @nemanjai , @compnerd

Any updates on this?

[compnerd]

Ah, okay. LGTM.

Do you need me to commit this on your behalf (as last time)?

[sarveshtamba]

Sure @compnerd, please go ahead and commit this on my behalf like last time. Thanks in advance!

[compnerd]

@sarveshtamba - just to make sure, you are aware that the license for LLVM has changed and that this work is acceptable to be published under the new license?

[sarveshtamba]

@compnerd - I will check this and let you know. In the meanwhile can you please point towards the new license documentation/details?

[compnerd]

Sure, the new license is at https://llvm.org/LICENSE.txt (Apache)

[sarveshtamba]

@compnerd - I got a confirmation that we can go ahead and merge this. Please go ahead and commit this on my behalf.

[sarveshtamba]

@compnerd - Please let me know once this is committed. Thanks.

[compnerd]

SVN r354045

[sarveshtamba]

@compnerd Has this been pushed upstream? I pulled latest code for Apple Swift master, and did not see this change in swift-llvm repository. Please confirm.

[sarveshtamba]

Can anyone confirm if this has been pushed upstream in the master branch? I pulled latest code for Apple Swift master, and did not see this change in swift-llvm repository.

[jsji]

@sarveshtamba As the author mentioned, yes, this has been upstreamed.

Note that this patch was actually splitted into two commits,
the first one in https://reviews.llvm.org/rL348970 for the __PPC__ macro,
the second one in https://reviews.llvm.org/rL354045.

However, looks like swift-llvm did not sync the repo timely( or correctly),
So it only contains rL348970 for now.

You'll either have to wait, or contact maintainer of swift-llvm to report the sync issue.

include/llvm/Support/Threading.h

 #include <functional>
 
 #if defined(_MSC_VER)
 // MSVC's call_once implementation worked since VS 2015, which is the minimum
 // supported version as of this writing.
 #define LLVM_THREADING_USE_STD_CALL_ONCE 1
 #elif defined(LLVM_ON_UNIX) &&                                                 \
     (defined(_LIBCPP_VERSION) ||                                               \
-     !(defined(__NetBSD__) || defined(__OpenBSD__) || defined(__ppc__)))
+     !(defined(__NetBSD__) || defined(__OpenBSD__) ||                          \
+       (defined(__ppc__) || defined(__PPC__))))
 // std::call_once from libc++ is used on all Unix platforms. Other
 // implementations like libstdc++ are known to have problems on NetBSD,
 // OpenBSD and PowerPC.
 #define LLVM_THREADING_USE_STD_CALL_ONCE 1
+#elif defined(LLVM_ON_UNIX) &&                                                 \
+    ((defined(__ppc__) || defined(__PPC__)) && defined(__LITTLE_ENDIAN__))
+// Check for PowerPC64LE to use std::call_once
+#define LLVM_THREADING_USE_STD_CALL_ONCE 1
 #else
 #define LLVM_THREADING_USE_STD_CALL_ONCE 0
 #endif
 
 #if LLVM_THREADING_USE_STD_CALL_ONCE
 #include <mutex>
 #else
 #include "llvm/Support/Atomic.h"