[clang] Fix KEYALL

[yaxunl]

Summary

Introduce KEYMAX and a generic way to update KEYALL.

[delcypher]

@yaxunl Thanks for addressing my feedback so quickly. I think the commit message should also mention that KEYCUDA is now included in KEYALL. Other than that LGTM.

[yaxunl]

In D125396#3506478, @delcypher wrote:

@yaxunl Thanks for addressing my feedback so quickly. I think the commit message should also mention that KEYCUDA is now included in KEYALL. Other than that LGTM.

will do when committing

clang/lib/Basic/IdentifierTable.cpp

enum {
     KEYZVECTOR    = 0x40000,
     KEYCOROUTINES = 0x80000,
     KEYMODULES    = 0x100000,
     KEYCXX20      = 0x200000,
     KEYOPENCLCXX  = 0x400000,
     KEYMSCOMPAT   = 0x800000,
     KEYSYCL       = 0x1000000,
     KEYCUDA       = 0x2000000,
+    KEYMAX        = KEYCUDA, // The maximum key
     KEYALLCXX = KEYCXX | KEYCXX11 | KEYCXX20,
-    KEYALL = (0x1ffffff & ~KEYNOMS18 &
-              ~KEYNOOPENCL) // KEYNOMS18 and KEYNOOPENCL are used to exclude.
+    KEYALL = (KEYMAX | (KEYMAX-1)) & ~KEYNOMS18 &
+             ~KEYNOOPENCL // KEYNOMS18 and KEYNOOPENCL are used to exclude.
   };
 
   /// How a keyword is treated in the selected standard.
   enum KeywordStatus {
     KS_Disabled,    // Disabled
     KS_Extension,   // Is an extension
     KS_Enabled,     // Enabled
     KS_Future       // Is a keyword in future standard