--cuda-host-only should not disable linking phase.

[tra]

Summary

Host-only cuda compilation does produce valid host object file and in some cases users do want to proceed on to the linking phase.
The change removes special case that stopped compilation pipeline at the Assembly phase.
Device-side compilation is still stopped early by the types::getCompilationPhases().

[samsonov]

Looks reasonable.

[echristo]

One inline comment.

-eric

test/Driver/cuda-options.cu

30

Grammar?

lib/Driver/Driver.cpp

// -{fsyntax-only,-analyze,emit-ast} only run up to the compiler.
                                         options::OPT__analyze_auto)) ||
              (PhaseArg = DAL.getLastArg(options::OPT_emit_ast))) {
     FinalPhase = phases::Compile;
 
     // -S only runs up to the backend.
   } else if ((PhaseArg = DAL.getLastArg(options::OPT_S))) {
     FinalPhase = phases::Backend;
 
-    // -c and partial CUDA compilations only run up to the assembler.
-  } else if ((PhaseArg = DAL.getLastArg(options::OPT_c)) ||
-             (PhaseArg = DAL.getLastArg(options::OPT_cuda_device_only)) ||
-             (PhaseArg = DAL.getLastArg(options::OPT_cuda_host_only))) {
+    // -c compilation only runs up to the assembler.
+  } else if ((PhaseArg = DAL.getLastArg(options::OPT_c))) {
     FinalPhase = phases::Assemble;
 
     // Otherwise do everything.
   } else
     FinalPhase = phases::Link;
 
   if (FinalPhaseArg)
     *FinalPhaseArg = PhaseArg;

test/Driver/cuda-options.cu

 // RUN:   -check-prefix CUDA-L %s
 
 // Verify that -cuda-no-device disables device-side compilation and linking
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-host-only %s 2>&1 \
 // Make sure we didn't run device-side compilation.
 // RUN:   | FileCheck -check-prefix CUDA-ND \
 // Then compile host side and make sure we don't attempt to incorporate GPU code.
 // RUN:    -check-prefix CUDA-H -check-prefix CUDA-H-NI \
-// Make sure we don't link anything.
-// RUN:    -check-prefix CUDA-NL %s
+// Make linking is allowed to happen, even if we're missing GPU code.
+// RUN:    -check-prefix CUDA-L %s
 
 // Verify that -cuda-no-host disables host-side compilation and linking
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-device-only %s 2>&1 \
 // Compile device-side to PTX assembly
 // RUN:   | FileCheck -check-prefix CUDA-D1 \
 // Make sure there are no host cmpilation or linking.
 // RUN:   -check-prefix CUDA-NH -check-prefix CUDA-NL %s