Index: docs/CommandGuide/FileCheck.rst
===================================================================
--- docs/CommandGuide/FileCheck.rst
+++ docs/CommandGuide/FileCheck.rst
@@ -77,6 +77,15 @@
   -verify``. With this option FileCheck will verify that input does not contain
   warnings not covered by any ``CHECK:`` patterns.
 
+.. option:: --enable-var-scope
+
+  Enables scope for regex variables.
+
+  Variables with names that start with ``$`` are considered global and
+  remain set throughout the file.
+
+  All other variables get undefined after each encountered ``CHECK-LABEL``.
+
 .. option:: -version
 
  Show the version number of this program.
@@ -344,6 +353,9 @@
 other unique identifiers. Conceptually, the presence of ``CHECK-LABEL`` divides
 the input stream into separate blocks, each of which is processed independently,
 preventing a ``CHECK:`` directive in one block matching a line in another block.
+If ``--enable-var-scope`` is in effect, all local variables are cleared at the
+beginning of the block.
+
 For example,
 
 .. code-block:: llvm
@@ -436,6 +448,13 @@
 Can be useful if you want the operands of ``op`` to be the same register,
 and don't care exactly which register it is.
 
+If ``--enable-var-scope`` is in effect, variables with names that
+start with ``$`` are considered to be global. All others variables are
+local.  All local variables get undefined at the beginning of each
+CHECK-LABEL block. Global variables are not affected by CHECK-LABEL.
+This makes it easier to ensure that individual tests are not affected
+by variables set in preceding tests.
+
 FileCheck Expressions
 ~~~~~~~~~~~~~~~~~~~~~
 
Index: test/FileCheck/line-count.txt
===================================================================
--- test/FileCheck/line-count.txt
+++ test/FileCheck/line-count.txt
@@ -1,15 +1,15 @@
 ; RUN: FileCheck  -input-file %s %s
-2
-3 aaa
-4 bbb
-5 ccc
-6 CHECK: [[@LINE-3]] {{a}}aa
-7 CHECK: [[@LINE-3]] {{b}}bb
-8 CHECK: [[@LINE-3]] {{c}}cc
-9 foobar
-10 CHECK: [[@LINE-1]] {{foo}}bar
-11
-12 arst CHECK: [[@LINE]] {{a}}rst
-13
+; RUN: not FileCheck -check-prefix BAD -input-file %s %s
+3
+4 aaa
+5 bbb
+6 ccc
+7 CHECK: [[@LINE-3]] {{a}}aa
+8 CHECK: [[@LINE-3]] {{b}}bb
+9 CHECK: [[@LINE-3]] {{c}}cc
+10 foobar
+11 CHECK: [[@LINE-1]] {{foo}}bar
+12
+13 arst CHECK: [[@LINE]] {{a}}rst
 14
-
+15 BAD: [[@LINE:cant-have-regex]]
Index: test/FileCheck/regex-scope.txt
===================================================================
--- /dev/null
+++ test/FileCheck/regex-scope.txt
@@ -0,0 +1,23 @@
+// RUN: FileCheck -check-prefix CHECK -input-file %s %s
+// RUN: FileCheck -check-prefixes CHECK,GLOBAL -input-file %s %s
+// RUN: FileCheck -check-prefixes CHECK,LOCAL -input-file %s %s
+// RUN: FileCheck -check-prefixes CHECK,GLOBAL --enable-var-scope -input-file %s %s
+// RUN: not FileCheck -check-prefixes CHECK,LOCAL --enable-var-scope -input-file %s %s
+
+local
+global
+; CHECK: [[LOCAL:loc.*]]
+; CHECK: [[$GLOBAL:glo.*]]
+
+local2
+global2
+; CHECK: [[LOCAL]]2
+; CHECK: [[$GLOBAL]]2
+
+barrier:
+; CHECK-LABEL: barrier
+
+local3
+global3
+; LOCAL: [[LOCAL]]3
+; GLOBAL: [[$GLOBAL]]3
Index: utils/FileCheck/FileCheck.cpp
===================================================================
--- utils/FileCheck/FileCheck.cpp
+++ utils/FileCheck/FileCheck.cpp
@@ -73,6 +73,12 @@
              "Allows leading and trailing whitespace if --strict-whitespace\n"
              "is not also passed."));
 
+static cl::opt<bool> EnableVarScope(
+    "enable-var-scope", cl::init(false),
+    cl::desc("Enables scope for regex variables. Variables with names that\n"
+             "do not start with '$' will be reset at the beginning of\n"
+             "each CHECK-LABEL block."));
+
 typedef cl::list<std::string>::const_iterator prefix_iterator;
 
 //===----------------------------------------------------------------------===//
@@ -263,15 +269,19 @@
       // is relaxed, more strict check is performed in \c EvaluateExpression.
       bool IsExpression = false;
       for (unsigned i = 0, e = Name.size(); i != e; ++i) {
-        if (i == 0 && Name[i] == '@') {
-          if (NameEnd != StringRef::npos) {
-            SM.PrintMessage(SMLoc::getFromPointer(Name.data()),
-                            SourceMgr::DK_Error,
-                            "invalid name in named regex definition");
-            return true;
+        if (i == 0) {
+          if (Name[i] == '$')  // Global vars start with '$'
+            continue;
+          if (Name[i] == '@') {
+            if (NameEnd != StringRef::npos) {
+              SM.PrintMessage(SMLoc::getFromPointer(Name.data()),
+                              SourceMgr::DK_Error,
+                              "invalid name in named regex definition");
+              return true;
+            }
+            IsExpression = true;
+            continue;
           }
-          IsExpression = true;
-          continue;
         }
         if (Name[i] != '_' && !isalnum(Name[i]) &&
             (!IsExpression || (Name[i] != '+' && Name[i] != '-'))) {
@@ -1262,6 +1272,18 @@
   errs() << "\n";
 }
 
+// Remove local variables from \p VariableTable. Global variables
+// (start with '$') are preserved.
+static void ClearLocalVars(StringMap<StringRef> &VariableTable) {
+  SmallVector<StringRef, 16> LocalVars;
+  for (const auto &Var : VariableTable)
+    if (Var.first()[0] != '$')
+      LocalVars.push_back(Var.first());
+
+  for (const auto &Var : LocalVars)
+    VariableTable.erase(Var);
+}
+
 /// Check the input to FileCheck provided in the \p Buffer against the \p
 /// CheckStrings read from the check file.
 ///
@@ -1298,6 +1320,9 @@
       ++j;
     }
 
+    if (EnableVarScope)
+      ClearLocalVars(VariableTable);
+
     for (; i != j; ++i) {
       const CheckString &CheckStr = CheckStrings[i];