[OpenCL] Allow clk_event_t comparisons

[svenvh]

Summary

Also rename invalid-clk-events-cl2.0.cl to clk_event_t.cl and
repurpose it to include both positive and negative clk_event_t tests.

[mantognini]

LGTM, but please add a comment in the test file.

test/SemaOpenCL/clk_event_t.cl

3

It would be nice to have a comment saying this macro was extracted from the opencl-c.h header file.

lib/Sema/SemaExpr.cpp

QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
   if (!IsRelational && LHSIsNull
       && LHSType->isIntegerType() && RHSType->isBlockPointerType()) {
     LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
     return computeResultTy();
   }
 
   if (getLangOpts().OpenCLVersion >= 200) {
+    if (LHSType->isClkEventT() && RHSType->isClkEventT()) {
+      return computeResultTy();
+    }
+
     if (LHSType->isQueueT() && RHSType->isQueueT()) {
       return computeResultTy();
     }
 
     if (LHSIsNull && RHSType->isQueueT()) {
       LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
       return computeResultTy();
     }

test/SemaOpenCL/clk_event_t.cl

 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -cl-std=CL2.0
 
+#define CLK_NULL_EVENT (__builtin_astype(((void*)(__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;
+
+  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;
+}