[CMake] Make specifying invalid build type a fatal error (#72021)

This patch makes it so that specifying an invalid value for
CMAKE_BUILD_TYPE is a fatal error. Having this simply as a warning has
caused me (and probably others) a decent amount of headache. The check
was present before, but was proposed to be modified to a warning in
#60975 and changed to a
warning in c75dbed. This patch
reenables that behavior to hopefully reduce frustration for people
building LLVM in the common case while still allowing for alternative
build types to be setup without needing to perform source modification
through the addition of a CMake flag.

Author: boomanaiden154

llvm/CMakeLists.txt

@@ -392,9 +392,15 @@ endif()
 
 string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
 
+option(LLVM_ADDITIONAL_BUILD_TYPES "Additional build types that are allowed to be passed into CMAKE_BUILD_TYPE" "")
+
+set(ALLOWED_BUILD_TYPES DEBUG RELEASE RELWITHDEBINFO MINSIZEREL ${LLVM_ADDITIONAL_BUILD_TYPES})
+string (REPLACE ";" "|" ALLOWED_BUILD_TYPES_STRING "${ALLOWED_BUILD_TYPES}")
+string (TOUPPER "${ALLOWED_BUILD_TYPES_STRING}" uppercase_ALLOWED_BUILD_TYPES)
+
 if (CMAKE_BUILD_TYPE AND
-    NOT uppercase_CMAKE_BUILD_TYPE MATCHES "^(DEBUG|RELEASE|RELWITHDEBINFO|MINSIZEREL)$")
-  message(WARNING "Unknown value for CMAKE_BUILD_TYPE: ${CMAKE_BUILD_TYPE}")
+    NOT uppercase_CMAKE_BUILD_TYPE MATCHES "^(${uppercase_ALLOWED_BUILD_TYPES})$")
+  message(FATAL_ERROR "Unknown value for CMAKE_BUILD_TYPE: ${CMAKE_BUILD_TYPE}")
 endif()
 
 # LLVM_INSTALL_PACKAGE_DIR needs to be declared prior to adding the tools

llvm/docs/CMake.rst

@@ -321,6 +321,11 @@ enabled sub-projects. Nearly all of these variable names begin with
   enabled or not.  A version of LLVM built with ABI breaking checks
   is not ABI compatible with a version built without it.
 
+**LLVM_ADDITIONAL_BUILD_TYPES**:LIST
+  Adding a semicolon separated list of additional build types to this flag
+  allows for them to be specified as values in CMAKE_BUILD_TYPE without
+  encountering a fatal error during the configuration process.
+
 **LLVM_UNREACHABLE_OPTIMIZE**:BOOL
   This flag controls the behavior of `llvm_unreachable()` in release build
   (when assertions are disabled in general). When ON (default) then