[CUDA] Make __GCC_ATOMIC_XXX_LOCK_FREE macros the same on host/device.

Summary:
This fixes a bug where we were unable to compile the following CUDA
file with libstdc++ (didn't try libc++):

  #include <future>
  void foo() { std::shared_future<int> x; }

The problem is that <future> only defines std::shared_future if
__GCC_ATOMIC_INT_LOCK_FREE > 1.  When we compiled this file for device,
the macro was set to 1, and then the class didn't exist at all.

Reviewers: tra

Subscribers: cfe-commits, jhen

Differential Revision: https://reviews.llvm.org/D24407

llvm-svn: 281089

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 535b6810356..15190594fc5 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -1768,6 +1768,12 @@ public:
     UseExplicitBitFieldAlignment = HostTarget->useExplicitBitFieldAlignment();
     ZeroLengthBitfieldBoundary = HostTarget->getZeroLengthBitfieldBoundary();
 
+    // This is a bit of a lie, but it controls __GCC_ATOMIC_XXX_LOCK_FREE, and
+    // we need those macros to be identical on host and device, because (among
+    // other things) they affect which standard library classes are defined, and
+    // we need all classes to be defined on both the host and device.
+    MaxAtomicInlineWidth = HostTarget->getMaxAtomicInlineWidth();
+
     // Properties intentionally not copied from host:
     // - LargeArrayMinWidth, LargeArrayAlign: Not visible across the
     //   host/device boundary.