Index: llvm/utils/lit/tests/lit.cfg
===================================================================
--- llvm/utils/lit/tests/lit.cfg
+++ llvm/utils/lit/tests/lit.cfg
@@ -43,10 +43,17 @@
     if directory:
         llvm_config.with_environment('PATH', directory, append_path=True)
 
+# This test suite calls %{lit} to test lit's behavior for the sample test
+# suites in %{inputs}.  This test suite's results are then determined in part
+# by %{lit}'s textual output, which includes the output of FileCheck calls
+# within %{inputs}'s test suites.  Thus, %{lit} clears environment variables
+# that can affect FileCheck's output.
 config.substitutions.append(('%{inputs}', os.path.join(
     config.test_source_root, 'Inputs')))
-config.substitutions.append(('%{lit}', "%%{python} %s" % (
-    os.path.join(lit_path, 'lit.py'),)))
+config.substitutions.append(('%{lit}',
+    "{env} %{{python}} {lit}".format(
+        env="env -u FILECHECK_OPTS -u FILECHECK_DUMP_INPUT_ON_FAILURE",
+        lit=os.path.join(lit_path, 'lit.py'))))
 config.substitutions.append(('%{python}', '"%s"' % (sys.executable)))
 
 # Enable coverage.py reporting, assuming the coverage module has been installed
Index: llvm/utils/lit/tests/shtest-run-at-line.py
===================================================================
--- llvm/utils/lit/tests/shtest-run-at-line.py
+++ llvm/utils/lit/tests/shtest-run-at-line.py
@@ -1,7 +1,7 @@
 # Check that -vv makes the line number of the failing RUN command clear.
 # (-v is actually sufficient in the case of the internal shell.)
 #
-# RUN: env -u FILECHECK_OPTS not %{lit} -j 1 -vv %{inputs}/shtest-run-at-line > %t.out
+# RUN: not %{lit} -j 1 -vv %{inputs}/shtest-run-at-line > %t.out
 # RUN: FileCheck --input-file %t.out %s
 #
 # END.