Index: docs/CommandGuide/lit.rst
===================================================================
--- docs/CommandGuide/lit.rst
+++ docs/CommandGuide/lit.rst
@@ -395,17 +395,18 @@
 :program:`lit` provides various patterns that can be used with the RUN command.
 These are defined in TestRunner.py. The base set of substitutions are:
 
- ========== ==============
-  Macro      Substitution
- ========== ==============
- %s         source path (path to the file currently being run)
- %S         source dir (directory of the file currently being run)
- %p         same as %S
- %{pathsep} path separator
- %t         temporary file name unique to the test
- %T         temporary directory unique to the test
- %%         %
- ========== ==============
+ ======================= ==============
+  Macro                   Substitution
+ ======================= ==============
+ %s                      source path (path to the file currently being run)
+ %S                      source dir (directory of the file currently being run)
+ %p                      same as %S
+ %{pathsep}              path separator
+ %t                      temporary file name unique to the test
+ %T                      temporary directory unique to the test
+ %{shared_output(LABEL)} temporary file name, identified by "LABEL", shared across all tests
+ %%                      %
+ ======================= ==============
 
 Other substitutions are provided that are variations on this base set and
 further substitution patterns can be defined by each test module. See the
Index: docs/TestingGuide.rst
===================================================================
--- docs/TestingGuide.rst
+++ docs/TestingGuide.rst
@@ -464,6 +464,12 @@
 
    Example: ``/home/user/llvm.build/test/MC/ELF/Output``
 
+``%{shared_output(LABEL)}``
+   File path to a temporary file name shared across all tests, identified by
+   LABEL. This is useful as a cache for generated resources.
+
+   Example: ``/home/user/llvm.build/test/Output/Shared/LABEL.tmp``
+
 ``%{pathsep}``
 
    Expands to the path separator, i.e. ``:`` (or ``;`` on Windows).
Index: utils/lit/lit/TestRunner.py
===================================================================
--- utils/lit/lit/TestRunner.py
+++ utils/lit/lit/TestRunner.py
@@ -829,6 +829,9 @@
     sourcepath = test.getSourcePath()
     sourcedir = os.path.dirname(sourcepath)
 
+    sharedOutputDir = os.path.join(test.suite.exec_root, 'Output', 'Shared')
+    sharedOutputDir += os.path.sep
+
     # Normalize slashes, if requested.
     if normalize_slashes:
         sourcepath = sourcepath.replace('\\', '/')
@@ -849,6 +852,8 @@
                           ('%t', tmpName),
                           ('%basename_t', baseName),
                           ('%T', tmpDir),
+                          ('%{shared_output\(([-+=._a-zA-Z0-9]+)\)}',
+                           '%s\\1.tmp' % (sharedOutputDir,)),
                           ('#_MARKER_#', '%')])
 
     # "%/[STpst]" should be normalized.
Index: utils/lit/lit/run.py
===================================================================
--- utils/lit/lit/run.py
+++ utils/lit/lit/run.py
@@ -1,4 +1,5 @@
 import os
+import shutil
 import sys
 import threading
 import time
@@ -136,6 +137,15 @@
                 return True
             win32api.SetConsoleCtrlHandler(console_ctrl_handler, True)
 
+        # Make fresh shared output directories.
+        suites = set(test.suite for test in self.tests)
+        print(suites)
+        for suite in suites:
+            shared_dir = os.path.join(suite.exec_root, 'Output', 'Shared')
+            shutil.rmtree(shared_dir, ignore_errors=True)
+            lit.util.mkdir_p(shared_dir)
+            print(shared_dir)
+
         # Save the display object on the runner so that we can update it from
         # our task completion callback.
         self.display = display
Index: utils/lit/tests/Inputs/shared-output/lit.cfg
===================================================================
--- /dev/null
+++ utils/lit/tests/Inputs/shared-output/lit.cfg
@@ -0,0 +1,6 @@
+import lit.formats
+config.name = 'shared-output'
+config.suffixes = ['.txt']
+config.test_format = lit.formats.ShTest()
+config.test_source_root = os.path.dirname(os.path.realpath(__file__))
+
Index: utils/lit/tests/Inputs/shared-output/primary.txt
===================================================================
--- /dev/null
+++ utils/lit/tests/Inputs/shared-output/primary.txt
@@ -0,0 +1,2 @@
+RUN: echo "primary" >> %{shared_output(SHARED)}
+RUN: echo "other" >> %{shared_output(OTHER)}
Index: utils/lit/tests/Inputs/shared-output/secondary.txt
===================================================================
--- /dev/null
+++ utils/lit/tests/Inputs/shared-output/secondary.txt
@@ -0,0 +1 @@
+RUN: echo "secondary" >> %{shared_output(SHARED)}
Index: utils/lit/tests/Inputs/shared-output/sub/sub.txt
===================================================================
--- /dev/null
+++ utils/lit/tests/Inputs/shared-output/sub/sub.txt
@@ -0,0 +1 @@
+RUN: echo "sub" >> %{shared_output(SHARED)}
Index: utils/lit/tests/shared-output.py
===================================================================
--- /dev/null
+++ utils/lit/tests/shared-output.py
@@ -0,0 +1,13 @@
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: echo 'lit_config.load_config(config, "%{inputs}/shared-output/lit.cfg")' > %t/lit.site.cfg
+# RUN: %{lit} %t
+# RUN: FileCheck %s < %t/Output/Shared/SHARED.tmp
+# RUN: FileCheck -check-prefix=NEGATIVE %s < %t/Output/Shared/SHARED.tmp
+# RUN: FileCheck -check-prefix=OTHER %s <  %t/Output/Shared/OTHER.tmp
+
+# CHECK-DAG: primary
+# CHECK-DAG: secondary
+# CHECK-DAG: sub
+
+# NEGATIVE-NOT: other
+# OTHER: other