clang/AMDGPU: Add missing __opencl_c_read_write_images feature macro (llvm#170307)

This is a partial fix for the rocm device-libs build. This
was most likely broken by 423bdb2

Author: arsenm

clang/lib/Basic/Targets/AMDGPU.h

@@ -316,8 +316,10 @@ class LLVM_LIBRARY_VISIBILITY AMDGPUTargetInfo final : public TargetInfo {
       Opts["cl_amd_media_ops"] = true;
       Opts["cl_amd_media_ops2"] = true;
 
+      // FIXME: Check subtarget for image support.
       Opts["__opencl_c_images"] = true;
       Opts["__opencl_c_3d_image_writes"] = true;
+      Opts["__opencl_c_read_write_images"] = true;
       Opts["cl_khr_3d_image_writes"] = true;
       Opts["__opencl_c_program_scope_global_variables"] = true;
       Opts["__opencl_c_atomic_order_seq_cst"] = true;

clang/test/Misc/amdgcn.languageOptsOpenCL.cl

@@ -162,6 +162,10 @@
   #ifndef __opencl_c_program_scope_global_variables
     #error "Missing __opencl_c_program_scope_global_variables define"
   #endif
+
+  #ifndef __opencl_c_read_write_images
+    #error "Missing __opencl_c_read_write_images define"
+  #endif
 #endif
 
 #if (__OPENCL_C_VERSION__ >= 300)