+function(llvm_replace_compiler_option var old new)
+ # Replaces a compiler option or switch `old' in `var' by `new'.
+ # If `old' is not in `var', appends `new' to `var'.
+ # Example: llvm_replace_compiler_option(CMAKE_CXX_FLAGS_RELEASE "-O3" "-O2")
+ # If the option already is on the variable, don't add it:
+ if( "${${var}}" MATCHES "(^| )${new}($| )" )
+ set(n "")
+ else()
+ set(n "${new}")
+ endif()
+ if( "${${var}}" MATCHES "(^| )${old}($| )" )
+ string( REGEX REPLACE "(^| )${old}($| )" " ${n} " ${var} "${${var}}" )
+ else()
+ set( ${var} "${${var}} ${n}" )
+ endif()
+ set( ${var} "${${var}}" PARENT_SCOPE )
+endfunction(llvm_replace_compiler_option)