[OpenCL] Define CLK_NULL_EVENT without cast

[svenvh]

Summary

Defining CLK_NULL_EVENT with a (void*) cast has the (unintended?)
side-effect that the address space will be fixed (as generic in OpenCL
2.0 mode). The consequence is that any target specific address space
for the clk_event_t type will not be applied.

It is not clear why the void pointer cast was needed in the first
place, and it seems we can do without it.

[Anastasia]

btw, there seems to be the same issue with reserve_id_t?

lib/Headers/opencl-c-base.h

416

Also I don't quite get why we are not just using value 0. I can't see anything relevant in the commit history. Not sure if @yaxunl can help.

Although it doesn't really block this change.

[svenvh]

In D63876#1565004, @Anastasia wrote:

btw, there seems to be the same issue with reserve_id_t?

Yes, CLK_NULL_RESERVE_ID has the same cast. I don't have any use case that is affected by it at the moment, so I left it out of this patch. But I can also update it if you prefer.

[Anastasia]

LGTM! Thanks!

If you like you can also change reserve_id_t. :)

lib/Headers/opencl-c-base.h

 #define CLK_INVALID_NDRANGE                         -160
 #define CLK_INVALID_EVENT_WAIT_LIST                 -57
 #define CLK_DEVICE_QUEUE_FULL                       -161
 #define CLK_INVALID_ARG_SIZE                        -51
 #define CLK_EVENT_ALLOCATION_FAILURE                -100
 #define CLK_OUT_OF_RESOURCES                        -5
 
 #define CLK_NULL_QUEUE                              0
-#define CLK_NULL_EVENT (__builtin_astype(((void*)(__SIZE_MAX__)), clk_event_t))
+#define CLK_NULL_EVENT (__builtin_astype(((__SIZE_MAX__)), clk_event_t))
 
 // execution model related definitions
 #define CLK_ENQUEUE_FLAGS_NO_WAIT                   0x0
 #define CLK_ENQUEUE_FLAGS_WAIT_KERNEL               0x1
 #define CLK_ENQUEUE_FLAGS_WAIT_WORK_GROUP           0x2
 
 typedef int kernel_enqueue_flags_t;
 typedef int clk_profiling_info;

test/SemaOpenCL/clk_event_t.cl

 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -cl-std=CL2.0
 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -cl-std=c++
 
 // Taken from opencl-c.h
-#define CLK_NULL_EVENT (__builtin_astype(((void*)(__SIZE_MAX__)), clk_event_t))
+#define CLK_NULL_EVENT (__builtin_astype(((__SIZE_MAX__)), clk_event_t))
 
 global clk_event_t ce; // expected-error {{the '__global clk_event_t' type cannot be used to declare a program scope variable}}
 
 int clk_event_tests() {
   event_t e;
   clk_event_t ce1;
   clk_event_t ce2;
+  clk_event_t ce3 = CLK_NULL_EVENT;
 
   if (e == ce1) { // expected-error {{invalid operands to binary expression ('event_t' and 'clk_event_t')}}
     return 9;
   }
 
   if (ce1 != ce2) {
     return 1;
   }
   else if (ce1 == CLK_NULL_EVENT || ce2 != CLK_NULL_EVENT) {
     return 0;
   }
 
   return 2;
 }