Merge commit 'cfca2297822d' from llvm.org/main into next

Author: git apple-llvm automerger

llvm/docs/AMDGPUUsage.rst

@@ -883,8 +883,9 @@ supported for the ``amdgcn`` target.
      Buffer Fat Pointer                    7               N/A         N/A              160     0
      Buffer Resource                       8               N/A         V#               128     0x00000000000000000000000000000000
      Buffer Strided Pointer (experimental) 9               *TODO*
-     *reserved for downstream use*         10
-     *reserved for downstream use*         11
+     *reserved for future use*             10
+     *reserved for future use*             11
+     *reserved for downstream use (LLPC)*  12
      Streamout Registers                   128             N/A         GS_REGS
      ===================================== =============== =========== ================ ======= ============================