# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
from lit.llvm.subst import ToolSubst

fc = ToolSubst('FileCheck', unresolved='fatal')
# the parent introduced the opposite rule, so we replace it if we see it.
if len(config.substitutions) > 0 and config.substitutions[0] == (fc.regex, 'FileCheck --allow-unused-prefixes=false'):
    config.substitutions[0] = (
        fc.regex, 'FileCheck --allow-unused-prefixes=true')
else:
    config.substitutions.insert(0, (fc.regex, 
                                    'FileCheck --allow-unused-prefixes=true'))