diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -448,6 +448,15 @@
   XCore
   )
 
+set(LLVM_ALL_EXPERIMENTAL_TARGETS
+  ARC
+  CSKY
+  DirectX
+  M68k
+  SPIRV
+  Xtensa
+)
+
 # List of targets with JIT support:
 set(LLVM_TARGETS_WITH_JIT X86 PowerPC AArch64 ARM Mips SystemZ)
 
@@ -455,7 +464,7 @@
     CACHE STRING "Semicolon-separated list of targets to build, or \"all\".")
 
 set(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD ""
-    CACHE STRING "Semicolon-separated list of experimental targets to build.")
+    CACHE STRING "Semicolon-separated list of experimental targets to build, or \"all\".")
 
 option(BUILD_SHARED_LIBS
   "Build all libraries as shared libraries instead of static" OFF)
@@ -544,6 +553,10 @@
   set( LLVM_TARGETS_TO_BUILD ${LLVM_ALL_TARGETS} )
 endif()
 
+if(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD STREQUAL "all")
+  set(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD ${LLVM_ALL_EXPERIMENTAL_TARGETS})
+endif()
+
 set(LLVM_TARGETS_TO_BUILD
    ${LLVM_TARGETS_TO_BUILD}
    ${LLVM_EXPERIMENTAL_TARGETS_TO_BUILD})