Add a -D flag to FileCheck to define variables

Summary:
This makes it very easy to test files that only differ in a constant
value somewhere in the test case.

Reviewers: jlebar, hfinkel, chandlerc, probinson

Reviewed By: probinson

Subscribers: probinson, llvm-commits

Differential Revision: https://reviews.llvm.org/D39629

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317572 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/FileCheck.rst

@@ -86,6 +86,11 @@ OPTIONS
 
   All other variables get undefined after each encountered ``CHECK-LABEL``.
 
+.. option:: -D<VAR=VALUE>
+
+  Sets a filecheck variable ``VAR`` with value ``VALUE`` that can be used in
+  ``CHECK:`` lines.
+
 .. option:: -version
 
  Show the version number of this program.

test/FileCheck/defines.txt

@@ -0,0 +1,9 @@
+; RUN: FileCheck -DVALUE=10 -input-file %s %s
+; RUN: not FileCheck -DVALUE=20 -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRMSG
+
+Value = 10
+; CHECK: Value = [[VALUE]]
+
+; ERRMSG: defines.txt:5:10: error: expected string not found in input
+; ERRMSG: defines.txt:1:1: note: with variable "VALUE" equal to "20"
+; ERRMSG: defines.txt:4:1: note: possible intended match here

utils/FileCheck/FileCheck.cpp

@@ -62,6 +62,10 @@ static cl::list<std::string> ImplicitCheckNot(
              "this pattern occur which are not matched by a positive pattern"),
     cl::value_desc("pattern"));
 
+static cl::list<std::string> GlobalDefines("D", cl::Prefix,
+    cl::desc("Define a variable to be used in capture patterns."),
+    cl::value_desc("VAR=VALUE"));
+
 static cl::opt<bool> AllowEmptyInput(
     "allow-empty", cl::init(false),
     cl::desc("Allow the input file to be empty. This is useful when making\n"
@@ -1295,6 +1299,9 @@ bool CheckInput(SourceMgr &SM, StringRef Buffer,
   /// VariableTable - This holds all the current filecheck variables.
   StringMap<StringRef> VariableTable;
 
+  for (const auto& Def : GlobalDefines)
+    VariableTable.insert(StringRef(Def).split('='));
+
   unsigned i = 0, j = 0, e = CheckStrings.size();
   while (true) {
     StringRef CheckRegion;