Index: llvm/utils/lit/lit/LitConfig.py
===================================================================
--- llvm/utils/lit/lit/LitConfig.py
+++ llvm/utils/lit/lit/LitConfig.py
@@ -26,7 +26,8 @@
                  maxIndividualTestTime = 0,
                  maxFailures = None,
                  parallelism_groups = {},
-                 echo_all_commands = False):
+                 echo_all_commands = False,
+                 debug_level = 0):
         # The name of the test runner.
         self.progname = progname
         # The items to add to the PATH environment variable.
@@ -68,6 +69,7 @@
         self.maxFailures = maxFailures
         self.parallelism_groups = parallelism_groups
         self.echo_all_commands = echo_all_commands
+        self.debug_level = debug_level
 
     @property
     def maxIndividualTestTime(self):
Index: llvm/utils/lit/lit/TestingConfig.py
===================================================================
--- llvm/utils/lit/lit/TestingConfig.py
+++ llvm/utils/lit/lit/TestingConfig.py
@@ -21,6 +21,9 @@
             'LLVM_DISABLE_CRASH_REPORT' : '1',
             }
 
+        if (litConfig.debug_level >= 2):
+            environment['FILECHECK_DUMP_INPUT_ON_FAILURE'] = '1'
+
         pass_vars = ['LIBRARY_PATH', 'LD_LIBRARY_PATH', 'SYSTEMROOT', 'TERM',
                      'CLANG', 'LD_PRELOAD', 'ASAN_OPTIONS', 'UBSAN_OPTIONS',
                      'LSAN_OPTIONS', 'ADB', 'ANDROID_SERIAL',
Index: llvm/utils/lit/lit/main.py
===================================================================
--- llvm/utils/lit/lit/main.py
+++ llvm/utils/lit/lit/main.py
@@ -201,10 +201,14 @@
 
 def main_with_tmp(builtinParameters):
     parser = argparse.ArgumentParser()
+    debug_level = 0
+    if os.getenv("LIT_DEBUG") == "1":
+        debug_level = 1
+    if os.getenv("LIT_DEBUG") == "2":
+        debug_level = 2
     parser.add_argument('test_paths',
                         nargs='*',
                         help='Files or paths to include in the test suite')
-
     parser.add_argument("--version", dest="show_version",
                       help="Show version and exit",
                       action="store_true", default=False)
@@ -233,7 +237,7 @@
                      action="store_true", default=False)
     format_group.add_argument("-vv", "--echo-all-commands",
                      dest="echoAllCommands",
-                     action="store_true", default=False,
+                     action="store_true", default=(debug_level >= 1),
                      help="Echo all commands as they are executed to stdout.\
                      In case of failure, last command shown will be the\
                      failing one.")
@@ -382,7 +386,8 @@
         maxIndividualTestTime = maxIndividualTestTime,
         maxFailures = opts.maxFailures,
         parallelism_groups = {},
-        echo_all_commands = opts.echoAllCommands)
+        echo_all_commands = opts.echoAllCommands,
+        debug_level = debug_level)
 
     # Perform test discovery.
     run = lit.run.Run(litConfig,
Index: llvm/utils/lit/tests/Inputs/test_verbose_filecheck
===================================================================
--- /dev/null
+++ llvm/utils/lit/tests/Inputs/test_verbose_filecheck
@@ -0,0 +1,13 @@
+; RUN: not FileCheck -input-file %s %s --check-prefix=CHECK1 --match-full-lines 2>&1 |  FileCheck %s --match-full-lines
+
+hello
+world
+
+; CHECK1: ciao
+; CHECK1-NEXT: world
+
+; CHECK: Full input was:
+; CHECK-NEXT: <<<<<<
+; CHECK: hello
+; CHECK: world
+; CHECK: >>>>>>
Index: llvm/utils/lit/tests/debug.py
===================================================================
--- /dev/null
+++ llvm/utils/lit/tests/debug.py
@@ -0,0 +1,3 @@
+# Check that LIT_DEBUG causes FileCheck to be verbose.
+
+# RUN: env LIT_DEBUG=2 %{lit} %{inputs}/test_verbose_filecheck
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
@@ -3,6 +3,8 @@
 #
 # RUN: not %{lit} -j 1 -vv %{inputs}/shtest-run-at-line > %t.out
 # RUN: FileCheck --input-file %t.out %s
+# RUN: env LIT_DEBUG=1 not %{lit} -j 1 %{inputs}/shtest-run-at-line > %t.out
+# RUN: FileCheck --input-file %t.out %s
 #
 # END.