[CUDA] Include CUDA headers before anything else.

Summary:
There's no point to --cuda-path if we then go and include /usr/include
first.  And if you install the right packages, Ubuntu will install (very
old) CUDA headers there.

Reviewers: tra

Subscribers: cfe-commits, Prazek

Differential Revision: https://reviews.llvm.org/D23341

llvm-svn: 278734

2 files changed, 10 insertions, 4 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 0efda4858f1..4900e20c484 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -410,6 +410,13 @@ void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,
     }
   }
 
+  // Add offload include arguments specific for CUDA.  This must happen before
+  // we -I or -include anything else, because we must pick up the CUDA headers
+  // from the particular CUDA installation, rather than from e.g.
+  // /usr/local/include.
+  if (JA.isOffloading(Action::OFK_Cuda))
+    getToolChain().AddCudaIncludeArgs(Args, CmdArgs);
+
   // Add -i* options, and automatically translate to
   // -include-pch/-include-pth for transparent PCH support. It's
   // wonky, but we include looking for .gch so we can support seamless
@@ -607,10 +614,6 @@ void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,
     // For IAMCU add special include arguments.
     getToolChain().AddIAMCUIncludeArgs(Args, CmdArgs);
   }
-
-  // Add offload include arguments specific for CUDA if that is required.
-  if (JA.isOffloading(Action::OFK_Cuda))
-    getToolChain().AddCudaIncludeArgs(Args, CmdArgs);
 }
 
 // FIXME: Move to target hook.
diff --git a/clang/test/Driver/cuda-detect.cu b/clang/test/Driver/cuda-detect.cu
index 4994fd69791..c4c177287a8 100644
--- a/clang/test/Driver/cuda-detect.cu
+++ b/clang/test/Driver/cuda-detect.cu
@@ -96,6 +96,9 @@
 // NOCUDAINC-NOT: "-internal-isystem" "{{.*}}/cuda/include"
 // CUDAINC-SAME: "-include" "__clang_cuda_runtime_wrapper.h"
 // NOCUDAINC-NOT: "-include" "__clang_cuda_runtime_wrapper.h"
+// -internal-externc-isystem flags must come *after* the cuda include flags,
+// because we must search the cuda include directory first.
+// CUDAINC-SAME: "-internal-externc-isystem"
 // COMMON-SAME: "-x" "cuda"
 // CHECK-CXXINCLUDE: clang{{.*}} "-cc1" "-triple" "nvptx64-nvidia-cuda"
 // CHECK-CXXINCLUDE-SAME: {{.*}}"-internal-isystem" "{{.+}}/include/c++/4.8"