[clang] [CUDA][HIP] Exclude external variables from constant promotion. (PR #73549)

[Levon Ter-Grigoryan via cfe-commits]

================
@@ -104,3 +106,17 @@ void fun() {
   (void) b<double>;
   (void) var_host_only;
 }
+
+// NEG-NOT: external_func
+extern __global__ void external_func();
+// NEG-NOT: @external_dep
+extern void* const external_dep[] = {
+  (void*)(external_func)
+};
+// NEG-NOT: @external_arr
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PatriosTheGreat wrote:

Not sure I got it correctly, but AFAIU in this test we are checking only the device code.
So with the current patch an external global variable should not be included to the device code (only to the host code) if it's not used in any device functions at the current compilation unit. If it's actually used 
Though if this variable is used at the device function than it should be manually marked as __constant__ variable. I can add this test case as well if it's needed.


https://github.com/llvm/llvm-project/pull/73549