FileCheck [8/12]: Define numeric var from expr

[thopre]

Summary

This patch is part of a patch series to add support for FileCheck
numeric expressions. This specific patch lift the restriction for a
numeric expression to either be a variable definition or a numeric
expression to try to match.

This commit allows a numeric variable to be set to the result of the
evaluation of a numeric expression after it has been matched
successfully. When it happens, the variable is allowed to be used on
the same line since its value is known at match time.

It also makes use of this possibility to reuse the parsing code to
parse a command-line definition by crafting a mirror string of the
-D option with the equal sign replaced by a colon sign, e.g. for option
'-D#NUMVAL=10' it creates the string
'-D#NUMVAL=10 (parsed as #NUMVAL:10)' where the numeric expression
is parsed to define NUMVAL. This result in a few tests needing updating
for the location diagnostics on top of the tests for the new feature.

It also enables empty numeric expression which match any number without
defining a variable. This is done here rather than in commit #5 of the
patch series because it requires to dissociate automatic regex insertion
in RegExStr from variable definition which would make commit #5 even
bigger than it already is.

Copyright:

• Linaro (changes up to diff 183612 of revision D55940)
• GraphCore (changes in later versions of revision D55940 and in new revision created off D55940)

[thopre]

Use camel case in new functions

[thopre]

Rebase

[thopre]

Make numeric variable constructor explicit

[thopre]

Rebase on latest changes

[thopre]

Rebase on latest changes

[thopre]

Run clang-format

[thopre]

Remove duplicate empty lines in numeric-expressions.txt

[thopre]

• Add checks in ParseExpr unit test to have same coverage as ParseNumericVariable
• Reorganize NumericVariableValueGetClearSet since variable can now be created undefined

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

Rebase on top of latest changes

[thopre]

rebase on top of latest changes

[thopre]

rebase on top of latest changes

[thopre]

Rebase on top of latest changes in patch series

[thopre]

Rebase on top of latest changes in the series

[thopre]

Rebase on latest changes in the patch series

[thopre]

Rebase on top of latest changes in the patch series

[thopre]

Rebase

[thopre]

Fix style for function parameter immediates

[arichardson]

llvm/include/llvm/Support/FileCheck.h

142

I would call this isKnownAtMatchTime() or isValueKnownAtMatchTime(). To me isMatchTimeKnown() sounds like "is the time of the match known?" which obviously doesn't make any sense in this context but the longer name means I know what the function does without find the documentation comment.

628

"if defining such a variable is invalid" slightly easier to parse for me.

644

Here and in the other functions: maybe use Optional<size_t> instead of a magic value of zero for line numbers?
I don't have a strong opinion here, I just think it might make it more obvious that the line number can also not be a line number but rather "this came from the command line".

llvm/lib/Support/FileCheck.cpp

54

I think !ExpressionAST is the more commonly used style.

[thopre]

• Rebase on latest changes in the patch series
• Address most comments

llvm/include/llvm/Support/FileCheck.h

644

I'll schedule a patch to that effect before this one since changing this might touch some area not currently touched by this patch. Keeping your comment open for now, will close it once I've added the patch to the patch series.

[thopre]

Rebase on top of latest changes in patch series

[thopre]

Add more unit tests

[jhenderson]

llvm/docs/CommandGuide/FileCheck.rst

632

If I'm not mistaken, the %<fmtspec> bit isn't implemented in this patch?

llvm/include/llvm/Support/FileCheck.h

113

Add to this comment what the value of the variable is if ExpressionAST is null.

llvm/lib/Support/FileCheck.cpp

28

This is unchecked in builds without assertions.

29–31

I'm not sure this second sentence is necessary?

30

I can't parse this string here. I can't even really figure out what this means to suggest an alternative.

538

You don't need the explicit StringRef(...) here. Just do MatchRegexp = "[0-9]+";

560

DefineCmdlineVariables doesn't conform to style guide. I haven't bothered looking it up, but I imagine this comment is a bit stale, or the function needs renaming?

1801

Suffix3? What happened to Suffix2?

Honestly, these names don't make a huge amount of sense to me.

Also, do we need all of them? As far as I can see, Suffix1 and Suffix3 are only used once each, so should just be inlined.

1804

DefNo -> DefIndex

("No" here is not sufficiently clear as to its context, IMO).

1814

Should this be parseNumericSubstitutionBlock?

1838

This comment sounds like a lie? You aren't skipping the error here...

1848–1857

"Parse the definition both to check that the syntax is correct and to create ..."

1861

Why is the expression being evaluated here? This probably needs a comment.

[thopre]

Address review comments

[thopre]

llvm/lib/Support/FileCheck.cpp

28

That's fine. setValue is called after substitution has happened and match was successful. Therefore ExpressionAST ought to evaluate fine. This is just in case code is reworked in the future and this invariant is broken.

[jhenderson]

llvm/lib/Support/FileCheck.cpp

28

It isn't. LLVM Errors and Expecteds HAVE to be checked. If they aren't it will lead to an abort. From the Programmer's Manual:

All Error instances, whether success or failure, must be either checked or moved from (via std::move or a return) before they are destructed. Accidentally discarding an unchecked error will cause a program abort at the point where the unchecked value’s destructor is run, making it easy to identify and fix violations of this rule.

[thopre]

Address review comments

llvm/lib/Support/FileCheck.cpp

28

Oh my bad, didn't make the connection with the Expected type. I think an abort would be fine in this case since that error should never occur in any of the executions. By that I mean that code path should be dead (that function will not be called if the expression does not evaluate). If it does, it's a bug somewhere in the code.

Does that make sense? I've added some comments on the expectation for the caller both in the declaration and just on top of the assert since that was missing.

[probinson]

llvm/docs/CommandGuide/FileCheck.rst

632

Where is <constraint> described?

llvm/lib/Support/FileCheck.cpp

31

You should check the Expected return value with something other than an assert. It is not sufficient to claim that the caller should call this only when the Expected result must be success. The contract for using Expected is that you will check the result. You could do something like

if (!EvaluatedValue || *EvaluatedValue != NewValue)
  llvm_unreachable("New value does not match expression for this variable");

463

? this should be the default, you should not have to say = StringRef() explicitly.

[jhenderson]

FTR, I haven't done a rigorous check of all the different new code paths to ensure you've got testing for them all, I'm afraid - the change is too large to sensibly do that, although I accept that it probably needs to be this large.

llvm/lib/Support/FileCheck.cpp

31

I think cantFail is intended for the kind of situation we're in here.

33

Isn't the assertion that the eval() function succeeded. In that case, let's talk about that. "Failed to evaluate expression when sanity checking variable value" or something to that effect.

1802

Won't this create a StringRef to a temporary?

1810

Append a copy of the command-line...

1821

Prefix1 + DefIndex + Prefix2 is used twice, once in each part of the if. If you factor it out into a separate variable, it'll be much easier to read, I think, and you can then get rid of Prefix1 and Prefix2 as separate variables. You can even fold them into the place where DefIndex is created, to avoid additional non-Twine string concatenations:

std::string SomeName = ("Global define #" + Twine(++I) + ": ").str();

1861

"Now evaluate the expression, whose value this variable should be set to, since the expression of a command-line variable definition should only use variables defined earlier on the command-line."

llvm/test/FileCheck/numeric-defines-diagnostics.txt

5

By the way, if you were to use --match-full-lines, you wouldn't need to use the regular expression in the last line of each of these checks, and your arrow would point closer to where it should be.

llvm/test/FileCheck/numeric-defines.txt

4–13

There should probably be a test case like the original, i.e. with no expression, just a literal numeric value.

llvm/test/FileCheck/numeric-expression.txt

97

This is allowed? That's surprising to me, although I suppose it's a natural consequence of the rules.

178

"when a variable"

180

Double dashes here, please.

Is it worth checking the error message in this context, to show that the failure is due to the expression match rather than due to something to do with the definition?

llvm/unittests/Support/FileCheckTest.cpp

86

Perhaps "Variable defined by numeric expression:" would make more sense.

89

"UseUnique" doesn't seem to line up with what this test is supposed to be doing, from what I can tell. What is "Unique" about it?

95

FoobarVar is the "undefined variable being set", right? In that case, I think a more purposeful name might be useful, e.g. FromVarExprVar or something like that. Happy with alternative names though.

333

I might be being dumb here, but where does the "same line" come into the following 4 EXPECTs?

400

How about EXPECT_FALSE/TRUE(Test.matchExpect(""));?

568

There are probably many other places where this is a problem already, but this should be ASSERT_TRUE, since the test cannot continue if it fails, and will crash on the next line (probably). Perhaps a separate commit to clean those up would be appropriate.

[thopre]

• Address review comments
• rebase on top of @LINE substitution fix

[jhenderson]

llvm/lib/Support/FileCheck.cpp

29

clang-format?

Rephrase the second string to "Value being set to different from variable evaluation"

1861

This comment hasn't been addressed.

llvm/test/FileCheck/numeric-defines-diagnostics.txt

5

This has been marked as Done, but I don't see any changes?

llvm/unittests/Support/FileCheckTest.cpp

86

I wanted the "Undefined" bit deleting. I don't think it's needed.

[thopre]

llvm/lib/Support/FileCheck.cpp

1861

I'm confused by what aspect of this you want to be explained. The reworded text seems to explain why is the expression evaluated but I thought you were asking why is it evaluated *here*. If the former, the text should be reworded further to remove the mention about errors and only say that the value of a variable can be given by an expression using variable earlier on the command line. If the latter, then the "only" becomes important since we are saying both that it is safe to evaluate now (we have the value of all variables) and that we should be doing it now (there is no input to match, all variables used are defined either from earlier command-line or from literal values).

llvm/test/FileCheck/numeric-defines-diagnostics.txt

5

Rather further away since the previous line would still need {{ and escaping for [ while the caret check would not need anything. It does reduce the amount of syntax for that line but it also make other lines slightly more difficult to read since I have to remote the space after the colon due to the --strict-whitespace:

NUMERRCLIFMT:Global defines:1:46: error: invalid variable name

Do you think it's worth doing? I can schedule a separate patch if yes.

llvm/test/FileCheck/numeric-expression.txt

97

As you said it's a natural consequence and I thought it could actually be useful (to check you have a number in an error message but don't care about the value) so I didn't forbid it.

llvm/unittests/Support/FileCheckTest.cpp

89

There is already a FooVarUse of type FileCheckNumericVariableUse. This one is a unique_ptr of that type. I've renamed into FooVarUsePtr.

568

Wasn't aware of ASSERT_TRUE. Another patch to schedule.

[thopre]

llvm/lib/Support/FileCheck.cpp

1861

Sorry, forgot to submit my replies. Done marks automatically get pushed when submitting a new revision.

llvm/test/FileCheck/numeric-defines-diagnostics.txt

5

Marked it done because I wrote a reply and was expecting an answer about whether you think it is actually worth it. In the event you think it is indeed worth it, I would only mark the answer as done once the work has been completed.

Unfortunately I forgot to submit my replies.

[thopre]

Fix more review comments

[jhenderson]

llvm/lib/Support/FileCheck.cpp

1861

The message content is fine as it stands in the current version. I've just suggested some grammar improvements. I think the meaning remains the same with them.

llvm/test/FileCheck/numeric-defines-diagnostics.txt

5

I guess it's not worth it. I just find the whole caret checking basically unreadable due to the regex as it stands. It feels quite fragile too.

Since you've got --strict-whitespace on, you could simplify the caret's line a little:
NUMERRCLIFMT-NEXT: {{^}} ^
(with appropriate numbers of spaces).

I don't think the trailing $ is important, really, in this case, but could be persuaded either way. In that case though, I'd put that in it's own {{$}} pattern. If you are happy with that, then please schedule a patch for that.

[probinson]

llvm/test/FileCheck/numeric-expression.txt

97

So [[#]] is equivalent to {{[0-9]+}} ? Might be worth a note in the documentation.

[thopre]

Address remaining review comments

[jhenderson]

LGTM, I think. You'd best get someone else (e.g. @probinson) to confirm too.

[probinson]

A couple of minor things, otherwise LGTM.

llvm/docs/CommandGuide/FileCheck.rst

638–639

constraint?

llvm/include/llvm/Support/FileCheck.h

114

"it is set from a value in the input" ? This is not a statement about what the ctor does, it sounds like an expectation.
"Otherwise, it should be set later from a value in the input." ?

[thopre]

• Remove reference to expression constraint, this is patch 11/12 material
• Clarify what the FileCheckNumericVariable constructor does and what is rather an expectation

[craig.topper]

llvm/trunk/lib/Support/FileCheck.cpp

345 ↗

(On Diff #211365)

gcc 7.3.1 seems to be unhappy with this line. I think it wants a std::move around ExpressionAST.

llvm/docs/CommandGuide/FileCheck.rst

.. option:: --enable-var-scope
 
   All other variables get undefined after each encountered ``CHECK-LABEL``.
 
 .. option:: -D<VAR=VALUE>
 
   Sets a filecheck pattern variable ``VAR`` with value ``VALUE`` that can be
   used in ``CHECK:`` lines.
 
-.. option:: -D#<NUMVAR>=<VALUE EXPRESSION>
+.. option:: -D#<NUMVAR>=<NUMERIC EXPRESSION>
 
   Sets a filecheck numeric variable ``NUMVAR`` to the result of evaluating
-  ``<VALUE EXPRESSION>`` that can be used in ``CHECK:`` lines. See section
-  ``FileCheck Numeric Variables and Expressions`` for details on the format
-  and meaning of ``<VALUE EXPRESSION>``.
+  ``<NUMERIC EXPRESSION>`` that can be used in ``CHECK:`` lines. See section
+  ``FileCheck Numeric Variables and Expressions`` for details on supported
+  numeric expressions.
 
 .. option:: -version
 
  Show the version number of this program.
 
 .. option:: -v
 
   Print good directive pattern matches.  However, if ``-input-dump=fail`` or

 
 .. code-block:: gas
 
     load r5, [r0]
     load r7, [r1]
 
 due to ``7`` being unequal to ``5 + 1``.
 
+A numeric variable can also be defined to the result of a numeric expression,
+in which case the numeric expression constraint is checked and if verified the
+variable is assigned to the value. The unified syntax for both defining numeric
+variables and checking a numeric expression is thus
+``[[#<NUMVAR>: <expr>]]`` with each element as described previously.
+
 The ``--enable-var-scope`` option has the same effect on numeric variables as
 on string variables.
 
 Important note: In its current implementation, an expression cannot use a
-numeric variable defined on the same line.
+numeric variable with a non-empty expression constraint defined on the same
+line.
 
 FileCheck Pseudo Numeric Variables
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Sometimes there's a need to verify output that contains line numbers of the
 match file, e.g. when testing compiler diagnostics.  This introduces a certain
 fragility of the match file structure, as "``CHECK:``" lines contain absolute
 line numbers in the same file, which have to be updated whenever line numbers

llvm/include/llvm/Support/FileCheck.h

 };
 
 /// Class representing a numeric variable and its associated current value.
 class FileCheckNumericVariable {
 private:
   /// Name of the numeric variable.
   StringRef Name;
 
+  /// Pointer to expression defining this numeric variable. Null for pseudo
+  /// variable whose value is known at parse time (e.g. @LINE pseudo variable)
+  /// or cleared local variable.
+  FileCheckExpressionAST *ExpressionAST;
+
   /// Value of numeric variable, if defined, or None otherwise.
   Optional<uint64_t> Value;
 
   /// Line number where this variable is defined, or None if defined before
   /// input is parsed. Used to determine whether a variable is defined on the
   /// same line as a given use.
   Optional<size_t> DefLineNumber;
 
 public:
   /// Constructor for a variable \p Name defined at line \p DefLineNumber or
-  /// defined before input is parsed if DefLineNumber is None.
+  /// defined before input is parsed if DefLineNumber is None. If not null,
+  /// the value of the variable is given by evaluating \p ExpressionAST.
+  /// Otherwise, it is set from a value in the input.
   FileCheckNumericVariable(StringRef Name,
-                           Optional<size_t> DefLineNumber = None)
-      : Name(Name), DefLineNumber(DefLineNumber) {}
+                           Optional<size_t> DefLineNumber = None,
+                           FileCheckExpressionAST *ExpressionAST = nullptr)
+      : Name(Name), ExpressionAST(ExpressionAST), DefLineNumber(DefLineNumber) {
+  }
 
   /// \returns name of this numeric variable.
   StringRef getName() const { return Name; }
 
   /// \returns this variable's value.
   Optional<uint64_t> getValue() const { return Value; }
 
-  /// Sets value of this numeric variable to \p NewValue.
-  void setValue(uint64_t NewValue) { Value = NewValue; }
+  /// \returns the pointer to the expression defining this numeric variable, if
+  /// any, or null otherwise.
+  FileCheckExpressionAST *getExpressionAST() const { return ExpressionAST; }
+
+  /// \returns whether this variable's value is known when performing the
+  /// substitutions of the line where it is defined.
+  bool isValueKnownAtMatchTime() const;
+
+  /// Sets value of this numeric variable to \p NewValue. Triggers an assertion
+  /// failure if the variable is defined by an expression and the expression
+  /// cannot be evaluated to be equal to \p NewValue.
+  void setValue(uint64_t NewValue);
 
   /// Clears value of this numeric variable, regardless of whether it is
   /// currently defined or not.
-  void clearValue() { Value = None; }
+  void clearValue() {
+    Value = None;
+    ExpressionAST = nullptr;
+  }
 
   /// \returns the line number where this variable is defined, if any, or None
   /// if defined before input is parsed.
   Optional<size_t> getDefLineNumber() { return DefLineNumber; }
 };
 
 /// Class representing the use of a numeric variable in the AST of an
 /// expression.
public:
 
   /// Parses the string at the start of \p Str for a variable name. \returns
   /// a VariableProperties structure holding the variable name and whether it
   /// is the name of a pseudo variable, or an error holding a diagnostic
   /// against \p SM if parsing fail. If parsing was successful, also strips
   /// \p Str from the variable name.
   static Expected<VariableProperties> parseVariable(StringRef &Str,
                                                     const SourceMgr &SM);
-  /// Parses \p Expr for the name of a numeric variable to be defined at line
-  /// \p LineNumber or before input is parsed if \p LineNumber is None.
-  /// \returns a pointer to the class instance representing that variable,
-  /// creating it if needed, or an error holding a diagnostic against \p SM
-  /// should defining such a variable be invalid.
-  static Expected<FileCheckNumericVariable *> parseNumericVariableDefinition(
-      StringRef &Expr, FileCheckPatternContext *Context,
-      Optional<size_t> LineNumber, const SourceMgr &SM);
-  /// Parses \p Expr for a numeric substitution block. Parameter
+  /// Parses \p Expr for a numeric substitution block at line \p LineNumber,
+  /// or before input is parsed if \p LineNumber is None. Parameter
   /// \p IsLegacyLineExpr indicates whether \p Expr should be a legacy @LINE
-  /// expression. \returns a pointer to the class instance representing the AST
-  /// of the expression whose value must be substituted, or an error holding a
-  /// diagnostic against \p SM if parsing fails. If substitution was
-  /// successful, sets \p DefinedNumericVariable to point to the class
-  /// representing the numeric variable being defined in this numeric
+  /// expression and \p Context points to the class instance holding the live
+  /// string and numeric variables. \returns a pointer to the class instance
+  /// representing the AST of the expression whose value must be substitued, or
+  /// an error holding a diagnostic against \p SM if parsing fails. If
+  /// substitution was successful, sets \p DefinedNumericVariable to point to
+  /// the class representing the numeric variable defined in this numeric
   /// substitution block, or None if this block does not define any variable.
-  Expected<std::unique_ptr<FileCheckExpressionAST>>
+  static Expected<std::unique_ptr<FileCheckExpressionAST>>
   parseNumericSubstitutionBlock(
       StringRef Expr,
       Optional<FileCheckNumericVariable *> &DefinedNumericVariable,
-      bool IsLegacyLineExpr, const SourceMgr &SM) const;
+      bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+      FileCheckPatternContext *Context, const SourceMgr &SM);
   /// Parses the pattern in \p PatternStr and initializes this FileCheckPattern
   /// instance accordingly.
   ///
   /// \p Prefix provides which prefix is being matched, \p Req describes the
   /// global options that influence the parsing such as whitespace
   /// canonicalization, \p SM provides the SourceMgr used for error reports.
   /// \returns true in case of an error, false otherwise.
   bool parsePattern(StringRef PatternStr, StringRef Prefix, SourceMgr &SM,
private:
   /// Finds the closing sequence of a regex variable usage or definition.
   ///
   /// \p Str has to point in the beginning of the definition (right after the
   /// opening sequence). \p SM holds the SourceMgr used for error repporting.
   ///  \returns the offset of the closing sequence within Str, or npos if it
   /// was not found.
   size_t FindRegexVarEnd(StringRef Str, SourceMgr &SM);
 
-  /// Parses \p Name as a (pseudo if \p IsPseudo is true) numeric variable use.
-  /// \returns the pointer to the class instance representing that variable if
-  /// successful, or an error holding a diagnostic against \p SM otherwise.
-  Expected<std::unique_ptr<FileCheckNumericVariableUse>>
+  /// Parses \p Expr for the name of a numeric variable to be defined at line
+  /// \p LineNumber, or before input is parsed if \p LineNumber is None.
+  /// \returns a pointer to the class instance representing that variable,
+  /// creating it if needed, or an error holding a diagnostic against \p SM
+  /// should defining such a variable be invalid.
+  static Expected<FileCheckNumericVariable *> parseNumericVariableDefinition(
+      StringRef &Expr, FileCheckPatternContext *Context,
+      Optional<size_t> LineNumber, FileCheckExpressionAST *ExpressionAST,
+      const SourceMgr &SM);
+  /// Parses \p Name as a (pseudo if \p IsPseudo is true) numeric variable use
+  /// at line \p LineNumber, or before input is parsed if \p LineNumber is
+  /// None. Parameter \p Context points to the class instance holding the live
+  /// string and numeric variables. \returns the pointer to the class instance
+  /// representing that variable if successful, or an error holding a
+  /// diagnostic against \p SM otherwise.
+  static Expected<std::unique_ptr<FileCheckNumericVariableUse>>
   parseNumericVariableUse(StringRef Name, bool IsPseudo,
-                          const SourceMgr &SM) const;
+                          Optional<size_t> LineNumber,
+                          FileCheckPatternContext *Context,
+                          const SourceMgr &SM);
   enum class AllowedOperand { LineVar, Literal, Any };
-  /// Parses \p Expr for use of a numeric operand. Accepts both literal values
-  /// and numeric variables, depending on the value of \p AO. \returns the
-  /// class representing that operand in the AST of the expression or an error
-  /// holding a diagnostic against \p SM otherwise.
-  Expected<std::unique_ptr<FileCheckExpressionAST>>
+  /// Parses \p Expr for use of a numeric operand at line \p LineNumber, or
+  /// before input is parsed if \p LineNumber is None. Accepts both literal
+  /// values and numeric variables, depending on the value of \p AO. Parameter
+  /// \p Context points to the class instance holding the live string and
+  /// numeric variables. \returns the class representing that operand in the
+  /// AST of the expression or an error holding a diagnostic against \p SM
+  /// otherwise.
+  static Expected<std::unique_ptr<FileCheckExpressionAST>>
   parseNumericOperand(StringRef &Expr, AllowedOperand AO,
-                      const SourceMgr &SM) const;
-  /// Parses \p Expr for a binary operation. The left operand of this binary
+                      Optional<size_t> LineNumber,
+                      FileCheckPatternContext *Context, const SourceMgr &SM);
+  /// Parses \p Expr for a binary operation at line \p LineNumber, or before
+  /// input is parsed if \p LineNumber is None. The left operand of this binary
   /// operation is given in \p LeftOp and \p IsLegacyLineExpr indicates whether
-  /// we are parsing a legacy @LINE expression. \returns the class representing
-  /// the binary operation in the AST of the expression, or an error holding a
-  /// diagnostic against \p SM otherwise.
-  Expected<std::unique_ptr<FileCheckExpressionAST>>
+  /// we are parsing a legacy @LINE expression. Parameter \p Context points to
+  /// the class instance holding the live string and numeric variables.
+  /// \returns the class representing the binary operation in the AST of the
+  /// expression, or an error holding a diagnostic against \p SM otherwise.
+  static Expected<std::unique_ptr<FileCheckExpressionAST>>
   parseBinop(StringRef &Expr, std::unique_ptr<FileCheckExpressionAST> LeftOp,
-             bool IsLegacyLineExpr, const SourceMgr &SM) const;
+             bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+             FileCheckPatternContext *Context, const SourceMgr &SM);
 };
 
 //===----------------------------------------------------------------------===//
 /// Summary of a FileCheck diagnostic.
 //===----------------------------------------------------------------------===//
 
 struct FileCheckDiag {
   /// What is the FileCheck directive for this diagnostic?
   Check::FileCheckType CheckTy;

llvm/lib/Support/FileCheck.cpp

 #include <cstdint>
 #include <list>
 #include <map>
 #include <tuple>
 #include <utility>
 
 using namespace llvm;
 
+bool FileCheckNumericVariable::isValueKnownAtMatchTime() const {
+  if (Value)
+    return true;
+
+  return ExpressionAST != nullptr;
+}
+
+void FileCheckNumericVariable::setValue(uint64_t NewValue) {
+  if (ExpressionAST != nullptr) {
+    // Caller is expected to call setValue only if substitution was successful.
+    assert(NewValue == cantFail(ExpressionAST->eval(),
+                                "Failed to evaluate associated expression when "
+                                "sanity checking value") &&
+           "Value being set to different from variable evaluation");
+  }
+  Value = NewValue;
+  // Clear pointer to AST to ensure it is not used after the numeric
+  // substitution defining this variable is processed since it's the
+  // substitution that owns the pointer.
+  ExpressionAST = nullptr;
+}
+
 Expected<uint64_t> FileCheckNumericVariableUse::eval() const {
   Optional<uint64_t> Value = NumericVariable->getValue();
   if (Value)
     return *Value;
+
+  FileCheckExpressionAST *ExpressionAST = NumericVariable->getExpressionAST();
+  if (!ExpressionAST)
     return make_error<FileCheckUndefVarError>(Name);
+
+  return ExpressionAST->eval();
 }
 
 Expected<uint64_t> FileCheckASTBinop::eval() const {
   Expected<uint64_t> LeftOp = LeftOperand->eval();
   Expected<uint64_t> RightOp = RightOperand->eval();
 
   // Bubble up any error (e.g. undefined variables) in the recursive
   // evaluation.

 
 char FileCheckUndefVarError::ID = 0;
 char FileCheckErrorDiagnostic::ID = 0;
 char FileCheckNotFoundError::ID = 0;
 
 Expected<FileCheckNumericVariable *>
 FileCheckPattern::parseNumericVariableDefinition(
     StringRef &Expr, FileCheckPatternContext *Context,
-    Optional<size_t> LineNumber, const SourceMgr &SM) {
+    Optional<size_t> LineNumber, FileCheckExpressionAST *ExpressionAST,
+    const SourceMgr &SM) {
   Expected<VariableProperties> ParseVarResult = parseVariable(Expr, SM);
   if (!ParseVarResult)
     return ParseVarResult.takeError();
   StringRef Name = ParseVarResult->Name;
 
   if (ParseVarResult->IsPseudo)
     return FileCheckErrorDiagnostic::get(
         SM, Name, "definition of pseudo numeric variable unsupported");
if (!Expr.empty())
     return FileCheckErrorDiagnostic::get(
         SM, Expr, "unexpected characters after numeric variable name");
 
   FileCheckNumericVariable *DefinedNumericVariable;
   auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
   if (VarTableIter != Context->GlobalNumericVariableTable.end())
     DefinedNumericVariable = VarTableIter->second;
   else
-    DefinedNumericVariable = Context->makeNumericVariable(Name, LineNumber);
+    DefinedNumericVariable =
+        Context->makeNumericVariable(Name, LineNumber, ExpressionAST);
 
   return DefinedNumericVariable;
 }
 
 Expected<std::unique_ptr<FileCheckNumericVariableUse>>
 FileCheckPattern::parseNumericVariableUse(StringRef Name, bool IsPseudo,
-                                          const SourceMgr &SM) const {
+                                          Optional<size_t> LineNumber,
+                                          FileCheckPatternContext *Context,
+                                          const SourceMgr &SM) {
   if (IsPseudo && !Name.equals("@LINE"))
     return FileCheckErrorDiagnostic::get(
         SM, Name, "invalid pseudo numeric variable '" + Name + "'");
 
   // Numeric variable definitions and uses are parsed in the order in which
   // they appear in the CHECK patterns. For each definition, the pointer to the
   // class instance of the corresponding numeric variable definition is stored
   // in GlobalNumericVariableTable in parsePattern. Therefore, if the pointer
   // we get below is null, it means no such variable was defined before. When
   // that happens, we create a dummy variable so that parsing can continue. All
   // uses of undefined variables, whether string or numeric, are then diagnosed
   // in printSubstitutions() after failing to match.
   auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
   FileCheckNumericVariable *NumericVariable;
   if (VarTableIter != Context->GlobalNumericVariableTable.end())
     NumericVariable = VarTableIter->second;
   else {
     NumericVariable = Context->makeNumericVariable(Name);
     Context->GlobalNumericVariableTable[Name] = NumericVariable;
   }
 
   Optional<size_t> DefLineNumber = NumericVariable->getDefLineNumber();
-  if (DefLineNumber && LineNumber && *DefLineNumber == *LineNumber)
+  if (DefLineNumber && LineNumber && *DefLineNumber == *LineNumber &&
+      !NumericVariable->isValueKnownAtMatchTime())
     return FileCheckErrorDiagnostic::get(
         SM, Name,
-        "numeric variable '" + Name + "' defined on the same line as used");
+        "numeric variable '" + Name +
+            "' defined from input on the same line as used");
 
   return llvm::make_unique<FileCheckNumericVariableUse>(Name, NumericVariable);
 }
 
 Expected<std::unique_ptr<FileCheckExpressionAST>>
 FileCheckPattern::parseNumericOperand(StringRef &Expr, AllowedOperand AO,
-                                      const SourceMgr &SM) const {
+                                      Optional<size_t> LineNumber,
+                                      FileCheckPatternContext *Context,
+                                      const SourceMgr &SM) {
   if (AO == AllowedOperand::LineVar || AO == AllowedOperand::Any) {
     // Try to parse as a numeric variable use.
     Expected<FileCheckPattern::VariableProperties> ParseVarResult =
         parseVariable(Expr, SM);
     if (ParseVarResult)
       return parseNumericVariableUse(ParseVarResult->Name,
-                                     ParseVarResult->IsPseudo, SM);
+                                     ParseVarResult->IsPseudo, LineNumber,
+                                     Context, SM);
     if (AO == AllowedOperand::LineVar)
       return ParseVarResult.takeError();
     // Ignore the error and retry parsing as a literal.
     consumeError(ParseVarResult.takeError());
   }
 
   // Otherwise, parse it as a literal.
   uint64_t LiteralValue;
   if (!Expr.consumeInteger(/*Radix=*/10, LiteralValue))
     return llvm::make_unique<FileCheckExpressionLiteral>(LiteralValue);
 
   return FileCheckErrorDiagnostic::get(SM, Expr,
                                        "invalid operand format '" + Expr + "'");
 }
 
 static uint64_t add(uint64_t LeftOp, uint64_t RightOp) {
   return LeftOp + RightOp;
 }
 
 static uint64_t sub(uint64_t LeftOp, uint64_t RightOp) {
   return LeftOp - RightOp;
 }
 
-Expected<std::unique_ptr<FileCheckExpressionAST>>
-FileCheckPattern::parseBinop(StringRef &Expr,
-                             std::unique_ptr<FileCheckExpressionAST> LeftOp,
-                             bool IsLegacyLineExpr, const SourceMgr &SM) const {
+Expected<std::unique_ptr<FileCheckExpressionAST>> FileCheckPattern::parseBinop(
+    StringRef &Expr, std::unique_ptr<FileCheckExpressionAST> LeftOp,
+    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+    FileCheckPatternContext *Context, const SourceMgr &SM) {
   Expr = Expr.ltrim(SpaceChars);
   if (Expr.empty())
     return std::move(LeftOp);
 
   // Check if this is a supported operation and select a function to perform
   // it.
   SMLoc OpLoc = SMLoc::getFromPointer(Expr.data());
   char Operator = popFront(Expr);
Expected<std::unique_ptr<FileCheckExpressionAST>> FileCheckPattern::parseBinop(
   Expr = Expr.ltrim(SpaceChars);
   if (Expr.empty())
     return FileCheckErrorDiagnostic::get(SM, Expr,
                                          "missing operand in expression");
   // The second operand in a legacy @LINE expression is always a literal.
   AllowedOperand AO =
       IsLegacyLineExpr ? AllowedOperand::Literal : AllowedOperand::Any;
   Expected<std::unique_ptr<FileCheckExpressionAST>> RightOpResult =
-      parseNumericOperand(Expr, AO, SM);
+      parseNumericOperand(Expr, AO, LineNumber, Context, SM);
   if (!RightOpResult)
     return RightOpResult;
 
   Expr = Expr.ltrim(SpaceChars);
   return llvm::make_unique<FileCheckASTBinop>(EvalBinop, std::move(LeftOp),
                                               std::move(*RightOpResult));
 }
 
 Expected<std::unique_ptr<FileCheckExpressionAST>>
 FileCheckPattern::parseNumericSubstitutionBlock(
     StringRef Expr,
     Optional<FileCheckNumericVariable *> &DefinedNumericVariable,
-    bool IsLegacyLineExpr, const SourceMgr &SM) const {
-  // Parse the numeric variable definition.
+    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+    FileCheckPatternContext *Context, const SourceMgr &SM) {
+  std::unique_ptr<FileCheckExpressionAST> ExpressionAST = nullptr;
+  StringRef DefExpr = StringRef();
   DefinedNumericVariable = None;
+  // Save variable definition expression if any.
   size_t DefEnd = Expr.find(':');
   if (DefEnd != StringRef::npos) {
-    StringRef DefExpr = Expr.substr(0, DefEnd);
-    StringRef UseExpr = Expr.substr(DefEnd + 1);
-
-    UseExpr = UseExpr.ltrim(SpaceChars);
-    if (!UseExpr.empty())
-      return FileCheckErrorDiagnostic::get(
-          SM, UseExpr,
-          "unexpected string after variable definition: '" + UseExpr + "'");
-
-    DefExpr = DefExpr.ltrim(SpaceChars);
-    Expected<FileCheckNumericVariable *> ParseResult =
-        parseNumericVariableDefinition(DefExpr, Context, LineNumber, SM);
-    if (!ParseResult)
-      return ParseResult.takeError();
-    DefinedNumericVariable = *ParseResult;
-
-    return nullptr;
+    DefExpr = Expr.substr(0, DefEnd);
+    Expr = Expr.substr(DefEnd + 1);
   }
 
   // Parse the expression itself.
   Expr = Expr.ltrim(SpaceChars);
-  // The first operand in a legacy @LINE expression is always the @LINE pseudo
-  // variable.
+  if (!Expr.empty()) {
+    // The first operand in a legacy @LINE expression is always the @LINE
+    // pseudo variable.
     AllowedOperand AO =
         IsLegacyLineExpr ? AllowedOperand::LineVar : AllowedOperand::Any;
     Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
-      parseNumericOperand(Expr, AO, SM);
+        parseNumericOperand(Expr, AO, LineNumber, Context, SM);
     while (ParseResult && !Expr.empty()) {
-    ParseResult =
-        parseBinop(Expr, std::move(*ParseResult), IsLegacyLineExpr, SM);
+      ParseResult = parseBinop(Expr, std::move(*ParseResult), IsLegacyLineExpr,
+                               LineNumber, Context, SM);
       // Legacy @LINE expressions only allow 2 operands.
       if (ParseResult && IsLegacyLineExpr && !Expr.empty())
         return FileCheckErrorDiagnostic::get(
             SM, Expr,
             "unexpected characters at end of expression '" + Expr + "'");
     }
     if (!ParseResult)
       return ParseResult;
-  return std::move(*ParseResult);
+    ExpressionAST = std::move(*ParseResult);
+  }
+
+  // Parse the numeric variable definition.
+  if (DefEnd != StringRef::npos) {
+    DefExpr = DefExpr.ltrim(SpaceChars);
+    Expected<FileCheckNumericVariable *> ParseResult =
+        parseNumericVariableDefinition(DefExpr, Context, LineNumber,
+                                       ExpressionAST.get(), SM);
+
+    if (!ParseResult)
+      return ParseResult.takeError();
+    DefinedNumericVariable = *ParseResult;
+  }
+
+  return ExpressionAST;
 }
 
 bool FileCheckPattern::parsePattern(StringRef PatternStr, StringRef Prefix,
                                     SourceMgr &SM,
                                     const FileCheckRequest &Req) {
   bool MatchFullLinesHere = Req.MatchFullLines && CheckTy != Check::CheckNot;
 
   PatternLoc = SMLoc::getFromPointer(PatternStr.data());
if (PatternStr.startswith("{{")) {
       if (AddRegExToRegEx(PatternStr.substr(2, End - 2), CurParen, SM))
         return true;
       RegExStr += ')';
 
       PatternStr = PatternStr.substr(End + 2);
       continue;
     }
 
-    // String and numeric substitution blocks. String substitution blocks come
+    // String and numeric substitution blocks. Pattern substitution blocks come
     // in two forms: [[foo:.*]] and [[foo]]. The former matches .* (or some
     // other regex) and assigns it to the string variable 'foo'. The latter
-    // substitutes foo's value. Numeric substitution blocks work the same way
-    // as string ones, but start with a '#' sign after the double brackets.
-    // Both string and numeric variable names must satisfy the regular
-    // expression "[a-zA-Z_][0-9a-zA-Z_]*" to be valid, as this helps catch
-    // some common errors.
+    // substitutes foo's value. Numeric substitution blocks recognize the same
+    // form as string ones, but start with a '#' sign after the double
+    // brackets. They also accept a combined form which sets a numeric variable
+    // to the evaluation of an expression. Both string and numeric variable
+    // names must satisfy the regular expression "[a-zA-Z_][0-9a-zA-Z_]*" to be
+    // valid, as this helps catch some common errors.
     if (PatternStr.startswith("[[")) {
       StringRef UnparsedPatternStr = PatternStr.substr(2);
       // Find the closing bracket pair ending the match.  End is going to be an
       // offset relative to the beginning of the match string.
       size_t End = FindRegexVarEnd(UnparsedPatternStr, SM);
       StringRef MatchStr = UnparsedPatternStr.substr(0, End);
       bool IsNumBlock = MatchStr.consume_front("#");
 
       if (End == StringRef::npos) {
         SM.PrintMessage(SMLoc::getFromPointer(PatternStr.data()),
                         SourceMgr::DK_Error,
                         "Invalid substitution block, no ]] found");
         return true;
       }
       // Strip the substitution block we are parsing. End points to the start
       // of the "]]" closing the expression so account for it in computing the
       // index of the first unparsed character.
       PatternStr = UnparsedPatternStr.substr(End + 2);
 
       bool IsDefinition = false;
+      bool SubstNeeded = false;
       // Whether the substitution block is a legacy use of @LINE with string
       // substitution block syntax.
       bool IsLegacyLineExpr = false;
       StringRef DefName;
       StringRef SubstStr;
       StringRef MatchRegexp;
       size_t SubstInsertIdx = RegExStr.size();
 
       // Parse string variable or legacy @LINE expression.
       if (!IsNumBlock) {
         size_t VarEndIdx = MatchStr.find(":");
         size_t SpacePos = MatchStr.substr(0, VarEndIdx).find_first_of(" \t");
         if (SpacePos != StringRef::npos) {
           SM.PrintMessage(SMLoc::getFromPointer(MatchStr.data() + SpacePos),
                           SourceMgr::DK_Error, "unexpected whitespace");
           return true;
         }
 
         // Get the name (e.g. "foo") and verify it is well formed.
         StringRef OrigMatchStr = MatchStr;
         Expected<FileCheckPattern::VariableProperties> ParseVarResult =
             parseVariable(MatchStr, SM);
         if (!ParseVarResult) {
           logAllUnhandledErrors(ParseVarResult.takeError(), errs());
           return true;
         }
         StringRef Name = ParseVarResult->Name;
         bool IsPseudo = ParseVarResult->IsPseudo;
 
         IsDefinition = (VarEndIdx != StringRef::npos);
+        SubstNeeded = !IsDefinition;
         if (IsDefinition) {
           if ((IsPseudo || !MatchStr.consume_front(":"))) {
             SM.PrintMessage(SMLoc::getFromPointer(Name.data()),
                             SourceMgr::DK_Error,
                             "invalid name in string variable definition");
             return true;
           }
 
if (PatternStr.startswith("[[")) {
       }
 
       // Parse numeric substitution block.
       std::unique_ptr<FileCheckExpressionAST> ExpressionAST;
       Optional<FileCheckNumericVariable *> DefinedNumericVariable;
       if (IsNumBlock) {
         Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
             parseNumericSubstitutionBlock(MatchStr, DefinedNumericVariable,
-                                          IsLegacyLineExpr, SM);
+                                          IsLegacyLineExpr, LineNumber, Context,
+                                          SM);
         if (!ParseResult) {
           logAllUnhandledErrors(ParseResult.takeError(), errs());
           return true;
         }
         ExpressionAST = std::move(*ParseResult);
+        SubstNeeded = ExpressionAST != nullptr;
         if (DefinedNumericVariable) {
           IsDefinition = true;
           DefName = (*DefinedNumericVariable)->getName();
-          MatchRegexp = StringRef("[0-9]+");
-        } else
+        }
+        if (SubstNeeded)
           SubstStr = MatchStr;
+        else
+          MatchRegexp = "[0-9]+";
       }
 
+      // Handle variable definition: [[<def>:(...)]] and [[#(...)<def>:(...)]].
+      if (IsDefinition) {
+        RegExStr += '(';
+        ++SubstInsertIdx;
+
+        if (IsNumBlock) {
+          FileCheckNumericVariableMatch NumericVariableDefinition = {
+              *DefinedNumericVariable, CurParen};
+          NumericVariableDefs[DefName] = NumericVariableDefinition;
+          // This store is done here rather than in match() to allow
+          // parseNumericVariableUse() to get the pointer to the class instance
+          // of the right variable definition corresponding to a given numeric
+          // variable use.
+          Context->GlobalNumericVariableTable[DefName] =
+              *DefinedNumericVariable;
+        } else {
+          VariableDefs[DefName] = CurParen;
+          // Mark string variable as defined to detect collisions between
+          // string and numeric variables in parseNumericVariableUse() and
+          // defineCmdlineVariables() when the latter is created later than the
+          // former. We cannot reuse GlobalVariableTable for this by populating
+          // it with an empty string since we would then lose the ability to
+          // detect the use of an undefined variable in match().
+          Context->DefinedVariableTable[DefName] = true;
+        }
+
+        ++CurParen;
+      }
+
+      if (!MatchRegexp.empty() && AddRegExToRegEx(MatchRegexp, CurParen, SM))
+        return true;
+
+      if (IsDefinition)
+        RegExStr += ')';
+
       // Handle substitutions: [[foo]] and [[#<foo expr>]].
-      if (!IsDefinition) {
+      if (SubstNeeded) {
         // Handle substitution of string variables that were defined earlier on
         // the same line by emitting a backreference. Expressions do not
         // support substituting a numeric variable defined on the same line.
         if (!IsNumBlock && VariableDefs.find(SubstStr) != VariableDefs.end()) {
           unsigned CaptureParenGroup = VariableDefs[SubstStr];
           if (CaptureParenGroup < 1 || CaptureParenGroup > 9) {
             SM.PrintMessage(SMLoc::getFromPointer(SubstStr.data()),
                             SourceMgr::DK_Error,
                             "Can't back-reference more than 9 variables");
             return true;
           }
           AddBackrefToRegEx(CaptureParenGroup);
         } else {
           // Handle substitution of string variables ([[<var>]]) defined in
           // previous CHECK patterns, and substitution of expressions.
           FileCheckSubstitution *Substitution =
               IsNumBlock
                   ? Context->makeNumericSubstitution(
                         SubstStr, std::move(ExpressionAST), SubstInsertIdx)
                   : Context->makeStringSubstitution(SubstStr, SubstInsertIdx);
           Substitutions.push_back(Substitution);
         }
-        continue;
       }
-
-      // Handle variable definitions: [[<def>:(...)]] and
-      // [[#(...)<def>:(...)]].
-      if (IsNumBlock) {
-        FileCheckNumericVariableMatch NumericVariableDefinition = {
-            *DefinedNumericVariable, CurParen};
-        NumericVariableDefs[DefName] = NumericVariableDefinition;
-        // This store is done here rather than in match() to allow
-        // parseNumericVariableUse() to get the pointer to the class instance
-        // of the right variable definition corresponding to a given numeric
-        // variable use.
-        Context->GlobalNumericVariableTable[DefName] = *DefinedNumericVariable;
-      } else {
-        VariableDefs[DefName] = CurParen;
-        // Mark the string variable as defined to detect collisions between
-        // string and numeric variables in parseNumericVariableUse() and
-        // DefineCmdlineVariables() when the latter is created later than the
-        // former. We cannot reuse GlobalVariableTable for this by populating
-        // it with an empty string since we would then lose the ability to
-        // detect the use of an undefined variable in match().
-        Context->DefinedVariableTable[DefName] = true;
-      }
-      RegExStr += '(';
-      ++CurParen;
-
-      if (AddRegExToRegEx(MatchRegexp, CurParen, SM))
-        return true;
-
-      RegExStr += ')';
     }
 
     // Handle fixed string matches.
     // Find the end, which is the start of the next regex.
     size_t FixedMatchEnd = PatternStr.find("{{");
     FixedMatchEnd = std::min(FixedMatchEnd, PatternStr.find("[["));
     RegExStr += Regex::escape(PatternStr.substr(0, FixedMatchEnd));
     PatternStr = PatternStr.substr(FixedMatchEnd);
if (CmdlineDefines.empty())
     return Error::success();
 
   // Create a string representing the vector of command-line definitions. Each
   // definition is on its own line and prefixed with a definition number to
   // clarify which definition a given diagnostic corresponds to.
   unsigned I = 0;
   Error Errs = Error::success();
   std::string CmdlineDefsDiag;
-  StringRef Prefix1 = "Global define #";
-  StringRef Prefix2 = ": ";
-  for (StringRef CmdlineDef : CmdlineDefines)
-    CmdlineDefsDiag +=
-        (Prefix1 + Twine(++I) + Prefix2 + CmdlineDef + "\n").str();
+  SmallVector<std::pair<size_t, size_t>, 4> CmdlineDefsIndices;
+  for (StringRef CmdlineDef : CmdlineDefines) {
+    std::string DefPrefix = ("Global define #" + Twine(++I) + ": ").str();
+    size_t EqIdx = CmdlineDef.find('=');
+    if (EqIdx == StringRef::npos) {
+      CmdlineDefsIndices.push_back(std::make_pair(CmdlineDefsDiag.size(), 0));
+      continue;
+    }
+    // Numeric variable definition.
+    if (CmdlineDef[0] == '#') {
+      // Append a copy of the command-line definition adapted to use the same
+      // format as in the input file to be able to reuse
+      // parseNumericSubstitutionBlock.
+      CmdlineDefsDiag += (DefPrefix + CmdlineDef + " (parsed as: [[").str();
+      std::string SubstitutionStr = CmdlineDef;
+      SubstitutionStr[EqIdx] = ':';
+      CmdlineDefsIndices.push_back(
+          std::make_pair(CmdlineDefsDiag.size(), SubstitutionStr.size()));
+      CmdlineDefsDiag += (SubstitutionStr + Twine("]])\n")).str();
+    } else {
+      CmdlineDefsDiag += DefPrefix;
+      CmdlineDefsIndices.push_back(
+          std::make_pair(CmdlineDefsDiag.size(), CmdlineDef.size()));
+      CmdlineDefsDiag += (CmdlineDef + "\n").str();
+    }
+  }
 
   // Create a buffer with fake command line content in order to display
   // parsing diagnostic with location information and point to the
   // global definition with invalid syntax.
   std::unique_ptr<MemoryBuffer> CmdLineDefsDiagBuffer =
       MemoryBuffer::getMemBufferCopy(CmdlineDefsDiag, "Global defines");
   StringRef CmdlineDefsDiagRef = CmdLineDefsDiagBuffer->getBuffer();
   SM.AddNewSourceBuffer(std::move(CmdLineDefsDiagBuffer), SMLoc());
 
-  SmallVector<StringRef, 4> CmdlineDefsDiagVec;
-  CmdlineDefsDiagRef.split(CmdlineDefsDiagVec, '\n', -1 /*MaxSplit*/,
-                           false /*KeepEmpty*/);
-  for (StringRef CmdlineDefDiag : CmdlineDefsDiagVec) {
-    unsigned DefStart = CmdlineDefDiag.find(Prefix2) + Prefix2.size();
-    StringRef CmdlineDef = CmdlineDefDiag.substr(DefStart);
-    size_t EqIdx = CmdlineDef.find('=');
-    if (EqIdx == StringRef::npos) {
+  for (std::pair<size_t, size_t> CmdlineDefIndices : CmdlineDefsIndices) {
+    StringRef CmdlineDef = CmdlineDefsDiagRef.substr(CmdlineDefIndices.first,
+                                                     CmdlineDefIndices.second);
+    if (CmdlineDef.empty()) {
       Errs = joinErrors(
           std::move(Errs),
           FileCheckErrorDiagnostic::get(
               SM, CmdlineDef, "missing equal sign in global definition"));
       continue;
     }
 
     // Numeric variable definition.
     if (CmdlineDef[0] == '#') {
-      StringRef CmdlineName = CmdlineDef.substr(1, EqIdx - 1);
-      Expected<FileCheckNumericVariable *> ParseResult =
-          FileCheckPattern::parseNumericVariableDefinition(CmdlineName, this,
-                                                           None, SM);
-      if (!ParseResult) {
-        Errs = joinErrors(std::move(Errs), ParseResult.takeError());
+      // Now parse the definition both to check that the syntax is correct and
+      // to create the necessary class instance.
+      StringRef CmdlineDefExpr = CmdlineDef.substr(1);
+      Optional<FileCheckNumericVariable *> DefinedNumericVariable;
+      Expected<std::unique_ptr<FileCheckExpressionAST>> ExpressionASTResult =
+          FileCheckPattern::parseNumericSubstitutionBlock(
+              CmdlineDefExpr, DefinedNumericVariable, false, None, this, SM);
+      if (!ExpressionASTResult) {
+        Errs = joinErrors(std::move(Errs), ExpressionASTResult.takeError());
         continue;
       }
-
-      StringRef CmdlineVal = CmdlineDef.substr(EqIdx + 1);
-      uint64_t Val;
-      if (CmdlineVal.getAsInteger(10, Val)) {
-        Errs = joinErrors(std::move(Errs),
-                          FileCheckErrorDiagnostic::get(
-                              SM, CmdlineVal,
-                              "invalid value in numeric variable definition '" +
-                                  CmdlineVal + "'"));
+      std::unique_ptr<FileCheckExpressionAST> ExpressionAST =
+          std::move(*ExpressionASTResult);
+      // Evaluate now the expression whose value this variable should be set to
+      // since the expression of a command-line variable definition should only
+      // use variable defined earlier on the command-line. If not, this is an
+      // error and we report it.
+      Expected<uint64_t> Value = ExpressionAST->eval();
+      if (!Value) {
+        Errs = joinErrors(std::move(Errs), Value.takeError());
         continue;
       }
-      FileCheckNumericVariable *DefinedNumericVariable = *ParseResult;
-      DefinedNumericVariable->setValue(Val);
+
+      assert(DefinedNumericVariable && "No variable defined");
+      (*DefinedNumericVariable)->setValue(*Value);
 
       // Record this variable definition.
-      GlobalNumericVariableTable[DefinedNumericVariable->getName()] =
-          DefinedNumericVariable;
+      GlobalNumericVariableTable[(*DefinedNumericVariable)->getName()] =
+          *DefinedNumericVariable;
     } else {
       // String variable definition.
       std::pair<StringRef, StringRef> CmdlineNameVal = CmdlineDef.split('=');
       StringRef CmdlineName = CmdlineNameVal.first;
       StringRef OrigCmdlineName = CmdlineName;
       Expected<FileCheckPattern::VariableProperties> ParseVarResult =
           FileCheckPattern::parseVariable(CmdlineName, SM);
       if (!ParseVarResult) {
if (CmdlineDef[0] == '#') {
         Errs = joinErrors(std::move(Errs), FileCheckErrorDiagnostic::get(
                                                SM, Name,
                                                "numeric variable with name '" +
                                                    Name + "' already exists"));
         continue;
       }
       GlobalVariableTable.insert(CmdlineNameVal);
       // Mark the string variable as defined to detect collisions between
-      // string and numeric variables in DefineCmdlineVariables when the latter
+      // string and numeric variables in defineCmdlineVariables when the latter
       // is created later than the former. We cannot reuse GlobalVariableTable
       // for this by populating it with an empty string since we would then
       // lose the ability to detect the use of an undefined variable in
       // match().
       DefinedVariableTable[Name] = true;
     }
   }
 

llvm/test/FileCheck/numeric-defines-diagnostics.txt

 ; Test incorrect syntax for -D# option is correctly diagnosed.
 
 ; Invalid variable name: starts with a digit.
 RUN: not FileCheck -D#10VALUE=10 --input-file %s %s 2>&1 \
 RUN:   | FileCheck %s --strict-whitespace --check-prefix NUMERRCLIFMT
 
-NUMERRCLIFMT: Global defines:1:20: error: invalid variable name
-NUMERRCLIFMT-NEXT: Global define #1: #10VALUE=10
-NUMERRCLIFMT-NEXT: {{^                   \^$}}
+NUMERRCLIFMT: Global defines:1:46: error: invalid variable name
+NUMERRCLIFMT-NEXT: Global define #1: #10VALUE=10 (parsed as: {{\[\[#10VALUE:10\]\]}})
+NUMERRCLIFMT-NEXT: {{^                                             \^$}}
 
 ; Invalid definition of pseudo variable.
 RUN: not FileCheck -D#@VALUE=10 --input-file %s %s 2>&1 \
 RUN:   | FileCheck %s --strict-whitespace --check-prefix NUMERRCLIPSEUDO
 
-NUMERRCLIPSEUDO: Global defines:1:20: error: definition of pseudo numeric variable unsupported
-NUMERRCLIPSEUDO-NEXT: Global define #1: #@VALUE=10
-NUMERRCLIPSEUDO-NEXT: {{^                   \^$}}
+NUMERRCLIPSEUDO: Global defines:1:45: error: definition of pseudo numeric variable unsupported
+NUMERRCLIPSEUDO-NEXT: Global define #1: #@VALUE=10 (parsed as: {{\[\[#@VALUE:10\]\]}})
+NUMERRCLIPSEUDO-NEXT: {{^                                            \^$}}
 
 ; Invalid definition of an expression.
 RUN: not FileCheck -D#VALUE+2=10 --input-file %s %s 2>&1 \
 RUN:   | FileCheck %s --strict-whitespace --check-prefix NUMERRCLITRAIL
 
-NUMERRCLITRAIL: Global defines:1:25: error: unexpected characters after numeric variable name
-NUMERRCLITRAIL-NEXT: Global define #1: #VALUE+2=10
-NUMERRCLITRAIL-NEXT: {{^                        \^$}}
-
-; Invalid value: numeric expression instead of literal.
-RUN: not FileCheck -D#VALUE1=3 -D#VALUE2='VALUE1 + 2' --input-file %s %s 2>&1 \
-RUN:   | FileCheck %s --strict-whitespace --check-prefix NUMERRCLIEXPR
-
-NUMERRCLIEXPR: Global defines:2:27: error: invalid value in numeric variable definition 'VALUE1 + 2'
-NUMERRCLIEXPR-NEXT: Global define #2: #VALUE2=VALUE1 + 2
-NUMERRCLIEXPR-NEXT: {{^                          \^$}}
+NUMERRCLITRAIL: Global defines:1:51: error: unexpected characters after numeric variable name
+NUMERRCLITRAIL-NEXT: Global define #1: #VALUE+2=10 (parsed as: {{\[\[#VALUE\+2:10\]\]}})
+NUMERRCLITRAIL-NEXT: {{^                                                  \^$}}

llvm/test/FileCheck/numeric-defines.txt

 ; Test functionality of -D# option: numeric variables are defined to the right
 ; value and CHECK directives using them match as expected given the value set.
 
-RUN: FileCheck -D#NUMVAL=12 --check-prefix CHECKNUM --input-file %s %s
-RUN: not FileCheck -D#NUMVAL=8 --check-prefix CHECKNUM --input-file %s %s 2>&1 \
-RUN:   | FileCheck %s --strict-whitespace --check-prefix NUMERRMSG
-RUN: not FileCheck -D#NUMVAL=12 --check-prefix NUMNOT --input-file %s %s 2>&1 \
-RUN:   | FileCheck %s --strict-whitespace --check-prefix NOT-NUMERRMSG
-RUN: FileCheck -D#NUMVAL=8 --check-prefixes NUMNOT --input-file %s %s
-
-Numeric value = 12
-CHECKNUM: Numeric value = [[#NUMVAL]]
-NUMNOT-NOT: Numeric value = [[#NUMVAL]]
-
-NUMERRMSG: defines.txt:[[#@LINE-3]]:11: error: CHECKNUM: expected string not found in input
-NUMERRMSG: defines.txt:1:1: note: scanning from here
-NUMERRMSG: defines.txt:1:1: note: with "NUMVAL" equal to "8"
-NUMERRMSG: defines.txt:[[#@LINE-7]]:1: note: possible intended match here
-
-NOT-NUMERRMSG: defines.txt:[[#@LINE-7]]:13: error: {{NUMNOT}}-NOT: excluded string found in input
-NOT-NUMERRMSG: defines.txt:[[#@LINE-10]]:1: note: found here
-NOT-NUMERRMSG: defines.txt:[[#@LINE-11]]:1: note: with "NUMVAL" equal to "12"
+RUN: FileCheck -D#NUMVAL1=8 -D#NUMVAL2='NUMVAL1 + 4' -check-prefixes CHECKNUM1,CHECKNUM2 -input-file %s %s
+RUN: not FileCheck -D#NUMVAL1=7 -D#NUMVAL2=12 -check-prefix CHECKNUM1 -input-file %s %s 2>&1 \
+RUN:   | FileCheck %s --strict-whitespace -check-prefix NUMERRMSG1
+RUN: not FileCheck -D#NUMVAL1=8 -D#NUMVAL2=8 -check-prefix CHECKNUM2 -input-file %s %s 2>&1 \
+RUN:   | FileCheck %s --strict-whitespace -check-prefix NUMERRMSG2
+RUN: not FileCheck -D#NUMVAL1=8 -D#NUMVAL2=8 -check-prefix NUMNOT -input-file %s %s 2>&1 \
+RUN:   | FileCheck %s --strict-whitespace -check-prefixes NOT-NUMERRMSG1
+RUN: not FileCheck -D#NUMVAL1=7 -D#NUMVAL2=12 -check-prefix NUMNOT -input-file %s %s 2>&1 \
+RUN:   | FileCheck %s --strict-whitespace -check-prefixes NOT-NUMERRMSG2
+RUN: FileCheck -D#NUMVAL1=7 -D#NUMVAL2=8 -check-prefixes NUMNOT -input-file %s %s
+
+Numeric value #1 = 8
+Numeric value #2 = 12
+CHECKNUM1: Numeric value #1 = [[#NUMVAL1]]
+CHECKNUM2: Numeric value #2 = [[#NUMVAL2]]
+NUMNOT-NOT: Numeric value #1 = [[#NUMVAL1]]
+NUMNOT-NOT: Numeric value #2 = [[#NUMVAL2]]
+
+NUMERRMSG1: defines.txt:[[#@LINE-5]]:12: error: CHECKNUM1: expected string not found in input
+NUMERRMSG1: defines.txt:1:1: note: scanning from here
+NUMERRMSG1: defines.txt:1:1: note: with "NUMVAL1" equal to "7"
+NUMERRMSG1: defines.txt:[[#@LINE-10]]:1: note: possible intended match here
+
+NUMERRMSG2: defines.txt:[[#@LINE-9]]:12: error: CHECKNUM2: expected string not found in input
+NUMERRMSG2: defines.txt:1:1: note: scanning from here
+NUMERRMSG2: defines.txt:1:1: note: with "NUMVAL2" equal to "8"
+NUMERRMSG2: defines.txt:[[#@LINE-14]]:1: note: possible intended match here
+
+NOT-NUMERRMSG1: defines.txt:[[#@LINE-13]]:13: error: {{NUMNOT}}-NOT: excluded string found in input
+NOT-NUMERRMSG1: defines.txt:[[#@LINE-18]]:1: note: found here
+NOT-NUMERRMSG1: defines.txt:[[#@LINE-19]]:1: note: with "NUMVAL1" equal to "8"
+
+NOT-NUMERRMSG2: defines.txt:[[#@LINE-16]]:13: error: {{NUMNOT}}-NOT: excluded string found in input
+NOT-NUMERRMSG2: defines.txt:[[#@LINE-21]]:1: note: found here
+NOT-NUMERRMSG2: defines.txt:[[#@LINE-22]]:1: note: with "NUMVAL2" equal to "12"

llvm/test/FileCheck/numeric-expression.txt

 ; Numeric expressions using more than one variable defined on other lines.
 USE MULTI VAR
 31
 42
 CHECK-LABEL: USE MULTI VAR
 CHECK-NEXT: [[#VAR2:]]
 CHECK-NEXT: [[#VAR1+VAR2]]
 
+; Numeric expression using a variable defined from a numeric expression.
+DEF EXPR GOOD MATCH
+42
+41 43
+; CHECK-LABEL: DEF EXPR GOOD MATCH
+; CHECK-NEXT: [[# VAR42:VAR1+31]]
+; CHECK-NEXT: [[# VAR41: VAR42-1]] [[# VAR41 + 2]]
+
+; Empty numeric expression.
+EMPTY NUM EXPR
+foo 104 bar
+; CHECK-LABEL: EMPTY NUM EXPR
+; CHECK-NEXT: foo [[#]] bar
+
 ; Numeric expression using undefined variables.
 RUN: not FileCheck --check-prefix UNDEF-USE --input-file %s %s 2>&1 \
 RUN:   | FileCheck --strict-whitespace --check-prefix UNDEF-USE-MSG %s
 
 UNDEF VAR USE
 UNDEFVAR: 11
 UNDEF-USE-LABEL: UNDEF VAR USE
 UNDEF-USE-NEXT: UNDEFVAR: [[#UNDEFVAR1+UNDEFVAR2]]

 INPUT-STR-CONFLICT-NEXT: {{C}}ONFLICT2: {{\[\[NUMVAR:foo\.\*\]\]}}
 INPUT-STR-CONFLICT-NEXT: {{^             \^$}}
 CLI-STR-CONFLICT: Global defines:2:19: error: numeric variable with name 'NUMVAR' already exists
 CLI-STR-CONFLICT-NEXT: Global define #2: NUMVAR=foobar
 CLI-STR-CONFLICT-NEXT: {{^                  \^$}}
 INPUT-NUM-CONFLICT: numeric-expression.txt:[[#@LINE-7]]:22: error: string variable with name 'STRVAR' already exists
 INPUT-NUM-CONFLICT-NEXT: CONFLICT4: redef2 {{\[\[#STRVAR:\]\]}}
 INPUT-NUM-CONFLICT-NEXT: {{^                     \^$}}
-CLI-NUM-CONFLICT: Global defines:2:20: error: string variable with name 'STRVAR' already exists
-CLI-NUM-CONFLICT-NEXT: Global define #2: #STRVAR=42
-CLI-NUM-CONFLICT-NEXT: {{^                   \^$}}
+CLI-NUM-CONFLICT: Global defines:2:45: error: string variable with name 'STRVAR' already exists
+CLI-NUM-CONFLICT-NEXT: Global define #2: #STRVAR=42 (parsed as: {{\[\[#STRVAR:42\]\]}})
+CLI-NUM-CONFLICT-NEXT: {{^                                            \^$}}
 
 ; Numeric variable definition with too big value.
 RUN: not FileCheck --check-prefix BIGVAL --input-file %s %s 2>&1 \
 RUN:   | FileCheck --strict-whitespace --check-prefix BIGVAL-MSG %s
 
 BIG VALUE
 NUMVAR: 10000000000000000000000
 BIGVAL-LABEL: BIG VALUE
 BIGVAL-NEXT: NUMVAR: [[#NUMVAR:]]
 BIGVAL-MSG: numeric-expression.txt:[[#@LINE-3]]:9: error: Unable to represent numeric value
 BIGVAL-MSG-NEXT: {{N}}UMVAR: 10000000000000000000000
 BIGVAL-MSG-NEXT: {{^        \^$}}
+
+; Verify that when a variable is set to an expression the expression is still
+; checked.
+RUN: not FileCheck --check-prefix DEF-EXPR-FAIL --input-file %s %s 2>&1 \
+RUN:   | FileCheck --strict-whitespace --check-prefix DEF-EXPR-FAIL-MSG %s
+
+DEF EXPR WRONG MATCH
+20
+43
+DEF-EXPR-FAIL-LABEL: DEF EXPR WRONG MATCH
+DEF-EXPR-FAIL-NEXT: [[# VAR20:]]
+DEF-EXPR-FAIL-NEXT: [[# VAR42: VAR20+22]]
+DEF-EXPR-FAIL-MSG: numeric-expression.txt:[[#@LINE-1]]:21: error: {{D}}EF-EXPR-FAIL-NEXT: is not on the line after the previous match
+DEF-EXPR-FAIL-MSG-NEXT: {{D}}EF-EXPR-FAIL-NEXT: {{\[\[# VAR42: VAR20\+22\]\]}}
+DEF-EXPR-FAIL-MSG-NEXT: {{^                    \^$}}

llvm/unittests/Support/FileCheckTest.cpp

 expectUndefErrors(std::unordered_set<std::string> ExpectedUndefVarNames,
                   Error Err) {
   handleAllErrors(std::move(Err), [&](const FileCheckUndefVarError &E) {
     ExpectedUndefVarNames.erase(E.getVarName());
   });
   EXPECT_TRUE(ExpectedUndefVarNames.empty()) << toString(ExpectedUndefVarNames);
 }
 
+// Return whether Err contains any FileCheckUndefVarError whose associated name
+// is not ExpectedUndefVarName.
 static void expectUndefError(const Twine &ExpectedUndefVarName, Error Err) {
   expectUndefErrors({ExpectedUndefVarName.str()}, std::move(Err));
 }
 
+uint64_t doAdd(uint64_t OpL, uint64_t OpR) { return OpL + OpR; }
+
 TEST_F(FileCheckTest, NumericVariable) {
-  // Undefined variable: getValue and eval fail, error returned by eval holds
-  // the name of the undefined variable.
+  // Undefined variable: isValueKnownAtMatchTime returns false, getValue and
+  // eval fail, error returned by eval holds the name of the undefined
+  // variable.
   FileCheckNumericVariable FooVar = FileCheckNumericVariable("FOO", 1);
   EXPECT_EQ("FOO", FooVar.getName());
+  EXPECT_FALSE(FooVar.isValueKnownAtMatchTime());
   FileCheckNumericVariableUse FooVarUse =
       FileCheckNumericVariableUse("FOO", &FooVar);
   EXPECT_FALSE(FooVar.getValue());
   Expected<uint64_t> EvalResult = FooVarUse.eval();
   EXPECT_FALSE(EvalResult);
   expectUndefError("FOO", EvalResult.takeError());
 
   FooVar.setValue(42);
 
-  // Defined variable: getValue and eval return value set.
+  // Defined variable: isValueKnownAtMatchTime returns true, getValue and eval
+  // return value set.
+  EXPECT_TRUE(FooVar.isValueKnownAtMatchTime());
   Optional<uint64_t> Value = FooVar.getValue();
   EXPECT_TRUE(bool(Value));
   EXPECT_EQ(42U, *Value);
   EvalResult = FooVarUse.eval();
   EXPECT_TRUE(bool(EvalResult));
   EXPECT_EQ(42U, *EvalResult);
 
+  // Variable defined by numeric expression: isValueKnownAtMatchTime
+  // returns true, getValue and eval return value of expression, setValue
+  // clears expression.
+  std::unique_ptr<FileCheckNumericVariableUse> FooVarUsePtr =
+      llvm::make_unique<FileCheckNumericVariableUse>("FOO", &FooVar);
+  std::unique_ptr<FileCheckExpressionLiteral> One =
+      llvm::make_unique<FileCheckExpressionLiteral>(1);
+  FileCheckASTBinop Binop =
+      FileCheckASTBinop(doAdd, std::move(FooVarUsePtr), std::move(One));
+  FileCheckNumericVariable FoobarExprVar =
+      FileCheckNumericVariable("FOOBAR", 2, &Binop);
+  EXPECT_TRUE(FoobarExprVar.isValueKnownAtMatchTime());
+  EXPECT_FALSE(FoobarExprVar.getValue());
+  FileCheckNumericVariableUse FoobarExprVarUse =
+      FileCheckNumericVariableUse("FOOBAR", &FoobarExprVar);
+  EvalResult = FoobarExprVarUse.eval();
+  EXPECT_TRUE(bool(EvalResult));
+  EXPECT_EQ(43U, *EvalResult);
+  EXPECT_TRUE(FoobarExprVar.getExpressionAST());
+  FoobarExprVar.setValue(43);
+  EXPECT_FALSE(FoobarExprVar.getExpressionAST());
+  FoobarExprVar = FileCheckNumericVariable("FOOBAR", 2, &Binop);
+  EXPECT_TRUE(FoobarExprVar.getExpressionAST());
+
   // Clearing variable: getValue and eval fail. Error returned by eval holds
   // the name of the cleared variable.
   FooVar.clearValue();
-  Value = FooVar.getValue();
-  EXPECT_FALSE(Value);
+  FoobarExprVar.clearValue();
+  EXPECT_FALSE(FoobarExprVar.getExpressionAST());
+  EXPECT_FALSE(FooVar.getValue());
+  EXPECT_FALSE(FoobarExprVar.getValue());
   EvalResult = FooVarUse.eval();
   EXPECT_FALSE(EvalResult);
   expectUndefError("FOO", EvalResult.takeError());
+  EvalResult = FoobarExprVarUse.eval();
+  EXPECT_FALSE(EvalResult);
+  expectUndefError("FOOBAR", EvalResult.takeError());
 }
 
-uint64_t doAdd(uint64_t OpL, uint64_t OpR) { return OpL + OpR; }
-
 TEST_F(FileCheckTest, Binop) {
-  FileCheckNumericVariable FooVar = FileCheckNumericVariable("FOO");
+  FileCheckNumericVariable FooVar = FileCheckNumericVariable("FOO", 1);
   FooVar.setValue(42);
   std::unique_ptr<FileCheckNumericVariableUse> FooVarUse =
       llvm::make_unique<FileCheckNumericVariableUse>("FOO", &FooVar);
-  FileCheckNumericVariable BarVar = FileCheckNumericVariable("BAR");
+  FileCheckNumericVariable BarVar = FileCheckNumericVariable("BAR", 2);
   BarVar.setValue(18);
   std::unique_ptr<FileCheckNumericVariableUse> BarVarUse =
       llvm::make_unique<FileCheckNumericVariableUse>("BAR", &BarVar);
   FileCheckASTBinop Binop =
       FileCheckASTBinop(doAdd, std::move(FooVarUse), std::move(BarVarUse));
 
   // Defined variable: eval returns right value.
   Expected<uint64_t> Value = Binop.eval();
PatternTester() {
     // a pattern for a different line.
     initNextPattern();
   }
 
   void initNextPattern() {
     P = FileCheckPattern(Check::CheckPlain, &Context, LineNumber++);
   }
 
-  bool parseNumVarDefExpect(StringRef Expr) {
-    StringRef ExprBufferRef = bufferize(SM, Expr);
-    return errorToBool(FileCheckPattern::parseNumericVariableDefinition(
-                           ExprBufferRef, &Context, LineNumber, SM)
-                           .takeError());
-  }
-
   bool parseSubstExpect(StringRef Expr) {
     StringRef ExprBufferRef = bufferize(SM, Expr);
     Optional<FileCheckNumericVariable *> DefinedNumericVariable;
-    return errorToBool(P.parseNumericSubstitutionBlock(
-                            ExprBufferRef, DefinedNumericVariable, false, SM)
-                           .takeError());
+    return errorToBool(
+        P.parseNumericSubstitutionBlock(ExprBufferRef, DefinedNumericVariable,
+                                        false, LineNumber - 1, &Context, SM)
   }
 
   bool parsePatternExpect(StringRef Pattern) {
     StringRef PatBufferRef = bufferize(SM, Pattern);
     return P.parsePattern(PatBufferRef, "CHECK", SM, Req);
   }
 
   bool matchExpect(StringRef Buffer) {
     StringRef BufferRef = bufferize(SM, Buffer);
     size_t MatchLen;
     return errorToBool(P.match(BufferRef, MatchLen, SM).takeError());
   }
 };
 
-TEST_F(FileCheckTest, ParseNumericVariableDefinition) {
-  PatternTester Tester;
-
-  // Invalid definition of pseudo.
-  EXPECT_TRUE(Tester.parseNumVarDefExpect("@LINE"));
-
-  // Conflict with pattern variable.
-  EXPECT_TRUE(Tester.parseNumVarDefExpect("BAR"));
-
-  // Defined variable.
-  EXPECT_FALSE(Tester.parseNumVarDefExpect("FOO"));
-}
-
 TEST_F(FileCheckTest, ParseExpr) {
   PatternTester Tester;
 
   // Variable definition.
 
   // Definition of invalid variable.
   EXPECT_TRUE(Tester.parseSubstExpect("10VAR:"));
   EXPECT_TRUE(Tester.parseSubstExpect("@FOO:"));
   EXPECT_TRUE(Tester.parseSubstExpect("@LINE:"));
 
+  // Conflict with pattern variable.
+  EXPECT_TRUE(Tester.parseSubstExpect("BAR:"));
+
   // Garbage after name of variable being defined.
   EXPECT_TRUE(Tester.parseSubstExpect("VAR GARBAGE:"));
 
-  // Variable defined to numeric expression.
-  EXPECT_TRUE(Tester.parseSubstExpect("VAR1: FOO"));
-
   // Acceptable variable definition.
   EXPECT_FALSE(Tester.parseSubstExpect("VAR1:"));
   EXPECT_FALSE(Tester.parseSubstExpect("  VAR2:"));
   EXPECT_FALSE(Tester.parseSubstExpect("VAR3  :"));
   EXPECT_FALSE(Tester.parseSubstExpect("VAR3:  "));
+  EXPECT_FALSE(Tester.parsePatternExpect("[[#FOOBAR: FOO+1]]"));
 
   // Numeric expression.
 
   // Unacceptable variable.
   EXPECT_TRUE(Tester.parseSubstExpect("10VAR"));
   EXPECT_TRUE(Tester.parseSubstExpect("@FOO"));
 
   // Only valid variable.
   EXPECT_FALSE(Tester.parseSubstExpect("@LINE"));
   EXPECT_FALSE(Tester.parseSubstExpect("FOO"));
   EXPECT_FALSE(Tester.parseSubstExpect("UNDEF"));
 
-  // Use variable defined on same line.
-  EXPECT_FALSE(Tester.parsePatternExpect("[[#LINE1VAR:]]"));
-  EXPECT_TRUE(Tester.parseSubstExpect("LINE1VAR"));
+  // Valid empty expression.
+  EXPECT_FALSE(Tester.parseSubstExpect(""));
+
+  // Valid use of variable defined on the same line from expression. Note that
+  // the same pattern object is used for the parsePatternExpect and
+  // parseSubstExpect since no initNextPattern is called, thus appearing as
+  // being on the same line from the pattern's point of view.
+  EXPECT_FALSE(Tester.parsePatternExpect("[[#LINE1VAR:FOO+1]]"));
+  EXPECT_FALSE(Tester.parseSubstExpect("LINE1VAR"));
+
+  // Invalid use of variable defined on same line from input. As above, the
+  // absence of a call to initNextPattern makes it appear to be on the same
+  // line from the pattern's point of view.
+  EXPECT_FALSE(Tester.parsePatternExpect("[[#LINE2VAR:]]"));
+  EXPECT_TRUE(Tester.parseSubstExpect("LINE2VAR"));
 
   // Unsupported operator.
   EXPECT_TRUE(Tester.parseSubstExpect("@LINE/2"));
 
   // Missing offset operand.
   EXPECT_TRUE(Tester.parseSubstExpect("@LINE+"));
 
   // Valid expression.
   EXPECT_FALSE(Tester.parseSubstExpect("@LINE+5"));
   EXPECT_FALSE(Tester.parseSubstExpect("FOO+4"));
+  EXPECT_FALSE(Tester.parseSubstExpect("FOOBAR"));
   Tester.initNextPattern();
   EXPECT_FALSE(Tester.parsePatternExpect("[[#FOO+FOO]]"));
   EXPECT_FALSE(Tester.parsePatternExpect("[[#FOO+3-FOO]]"));
 }
 
 TEST_F(FileCheckTest, ParsePattern) {
   PatternTester Tester;
 
TEST_F(FileCheckTest, ParsePattern) {
 
   // Valid pattern variable definition.
   EXPECT_FALSE(Tester.parsePatternExpect("[[PAT:[0-9]+]]"));
 
   // Invalid numeric expressions.
   EXPECT_TRUE(Tester.parsePatternExpect("[[#42INVALID]]"));
   EXPECT_TRUE(Tester.parsePatternExpect("[[#@FOO]]"));
   EXPECT_TRUE(Tester.parsePatternExpect("[[#@LINE/2]]"));
-  EXPECT_TRUE(Tester.parsePatternExpect("[[#YUP:@LINE]]"));
 
   // Valid numeric expressions and numeric variable definition.
   EXPECT_FALSE(Tester.parsePatternExpect("[[#FOO]]"));
   EXPECT_FALSE(Tester.parsePatternExpect("[[#@LINE+2]]"));
   EXPECT_FALSE(Tester.parsePatternExpect("[[#NUMVAR:]]"));
 }
 
 TEST_F(FileCheckTest, Match) {
   PatternTester Tester;
 
+  // Check matching an empty expression only matches a number.
+  Tester.parsePatternExpect("[[#]]");
+  EXPECT_TRUE(Tester.matchExpect("FAIL"));
+  EXPECT_FALSE(Tester.matchExpect("18"));
+
   // Check matching a definition only matches a number.
+  Tester.initNextPattern();
   Tester.parsePatternExpect("[[#NUMVAR:]]");
   EXPECT_TRUE(Tester.matchExpect("FAIL"));
+  EXPECT_TRUE(Tester.matchExpect(""));
   EXPECT_FALSE(Tester.matchExpect("18"));
 
   // Check matching the variable defined matches the correct number only
   Tester.initNextPattern();
   Tester.parsePatternExpect("[[#NUMVAR]] [[#NUMVAR+2]]");
   EXPECT_TRUE(Tester.matchExpect("19 21"));
   EXPECT_TRUE(Tester.matchExpect("18 21"));
   EXPECT_FALSE(Tester.matchExpect("18 20"));
 
   // Check matching a numeric expression using @LINE after match failure uses
   // the correct value for @LINE.
   Tester.initNextPattern();
   EXPECT_FALSE(Tester.parsePatternExpect("[[#@LINE]]"));
-  // Ok, @LINE is 4 now.
-  EXPECT_FALSE(Tester.matchExpect("4"));
+  // Ok, @LINE is 5 now.
+  EXPECT_FALSE(Tester.matchExpect("5"));
   Tester.initNextPattern();
-  // @LINE is now 5, match with substitution failure.
+  // @LINE is now 6, match with substitution failure.
   EXPECT_FALSE(Tester.parsePatternExpect("[[#UNKNOWN]]"));
   EXPECT_TRUE(Tester.matchExpect("FOO"));
   Tester.initNextPattern();
-  // Check that @LINE is 6 as expected.
+  // Check that @LINE is 7 as expected.
   EXPECT_FALSE(Tester.parsePatternExpect("[[#@LINE]]"));
-  EXPECT_FALSE(Tester.matchExpect("6"));
+  EXPECT_FALSE(Tester.matchExpect("7"));
 }
 
 TEST_F(FileCheckTest, Substitution) {
   SourceMgr SM;
   FileCheckPatternContext Context;
   std::vector<std::string> GlobalDefines;
   GlobalDefines.emplace_back(std::string("FOO=BAR"));
   EXPECT_FALSE(errorToBool(Context.defineCmdlineVariables(GlobalDefines, SM)));
 
   // Substitution of an undefined string variable fails and error holds that
   // variable's name.
   FileCheckStringSubstitution StringSubstitution =
       FileCheckStringSubstitution(&Context, "VAR404", 42);
   Expected<std::string> SubstValue = StringSubstitution.getResult();
   EXPECT_FALSE(bool(SubstValue));
   expectUndefError("VAR404", SubstValue.takeError());
 
   // Substitutions of defined pseudo and non-pseudo numeric variables return
   // the right value.
-  FileCheckNumericVariable LineVar = FileCheckNumericVariable("@LINE");
+  FileCheckNumericVariable LineVar = FileCheckNumericVariable("@LINE", 1);
+  FileCheckNumericVariable NVar = FileCheckNumericVariable("N", 1);
   LineVar.setValue(42);
-  FileCheckNumericVariable NVar = FileCheckNumericVariable("N");
   NVar.setValue(10);
   auto LineVarUse =
       llvm::make_unique<FileCheckNumericVariableUse>("@LINE", &LineVar);
   auto NVarUse = llvm::make_unique<FileCheckNumericVariableUse>("N", &NVar);
   FileCheckNumericSubstitution SubstitutionLine = FileCheckNumericSubstitution(
       &Context, "@LINE", std::move(LineVarUse), 12);
   FileCheckNumericSubstitution SubstitutionN =
       FileCheckNumericSubstitution(&Context, "N", std::move(NVarUse), 30);
TEST_F(FileCheckTest, FileCheckContext) {
 
   // Invalid numeric value for numeric variable.
   GlobalDefines.clear();
   GlobalDefines.emplace_back(std::string("#LocalNumVar=x"));
   EXPECT_TRUE(errorToBool(Cxt.defineCmdlineVariables(GlobalDefines, SM)));
 
   // Define local variables from command-line.
   GlobalDefines.clear();
+  // Clear local variables to remove dummy numeric variable x that
+  // parseNumericSubstitutionBlock would have created and stored in
+  // GlobalNumericVariableTable.
+  Cxt.clearLocalVars();
   GlobalDefines.emplace_back(std::string("LocalVar=FOO"));
   GlobalDefines.emplace_back(std::string("EmptyVar="));
-  GlobalDefines.emplace_back(std::string("#LocalNumVar=18"));
+  GlobalDefines.emplace_back(std::string("#LocalNumVar1=18"));
+  GlobalDefines.emplace_back(std::string("#LocalNumVar2=LocalNumVar1+2"));
   EXPECT_FALSE(errorToBool(Cxt.defineCmdlineVariables(GlobalDefines, SM)));
 
   // Check defined variables are present and undefined is absent.
   StringRef LocalVarStr = "LocalVar";
-  StringRef LocalNumVarRef = bufferize(SM, "LocalNumVar");
+  StringRef LocalNumVar1Ref = bufferize(SM, "LocalNumVar1");
+  StringRef LocalNumVar2Ref = bufferize(SM, "LocalNumVar2");
   StringRef EmptyVarStr = "EmptyVar";
   StringRef UnknownVarStr = "UnknownVar";
   Expected<StringRef> LocalVar = Cxt.getPatternVarValue(LocalVarStr);
   FileCheckPattern P = FileCheckPattern(Check::CheckPlain, &Cxt, 1);
   Optional<FileCheckNumericVariable *> DefinedNumericVariable;
   Expected<std::unique_ptr<FileCheckExpressionAST>> ExpressionAST =
-      P.parseNumericSubstitutionBlock(LocalNumVarRef, DefinedNumericVariable,
-                                      /*IsLegacyLineExpr=*/false, SM);
+      P.parseNumericSubstitutionBlock(LocalNumVar1Ref, DefinedNumericVariable,
+                                      /*IsLegacyLineExpr=*/false,
+                                      /*LineNumber=*/1, &Cxt, SM);
   EXPECT_TRUE(bool(LocalVar));
   EXPECT_EQ(*LocalVar, "FOO");
   Expected<StringRef> EmptyVar = Cxt.getPatternVarValue(EmptyVarStr);
   Expected<StringRef> UnknownVar = Cxt.getPatternVarValue(UnknownVarStr);
   EXPECT_TRUE(bool(ExpressionAST));
   Expected<uint64_t> ExpressionVal = (*ExpressionAST)->eval();
   EXPECT_TRUE(bool(ExpressionVal));
   EXPECT_EQ(*ExpressionVal, 18U);
+  ExpressionAST =
+      P.parseNumericSubstitutionBlock(LocalNumVar2Ref, DefinedNumericVariable,
+                                      /*IsLegacyLineExpr=*/false,
+                                      /*LineNumber=*/1, &Cxt, SM);
+  EXPECT_TRUE(bool(ExpressionAST));
+  ExpressionVal = (*ExpressionAST)->eval();
+  EXPECT_TRUE(bool(ExpressionVal));
+  EXPECT_EQ(*ExpressionVal, 20U);
   EXPECT_TRUE(bool(EmptyVar));
   EXPECT_EQ(*EmptyVar, "");
   EXPECT_TRUE(errorToBool(UnknownVar.takeError()));
 
   // Clear local variables and check they become absent.
   Cxt.clearLocalVars();
   LocalVar = Cxt.getPatternVarValue(LocalVarStr);
   EXPECT_TRUE(errorToBool(LocalVar.takeError()));
   // Check a numeric expression's evaluation fails if called after clearing of
   // local variables, if it was created before. This is important because local
   // variable clearing due to --enable-var-scope happens after numeric
   // expressions are linked to the numeric variables they use.
   EXPECT_TRUE(errorToBool((*ExpressionAST)->eval().takeError()));
   P = FileCheckPattern(Check::CheckPlain, &Cxt, 2);
   ExpressionAST = P.parseNumericSubstitutionBlock(
-      LocalNumVarRef, DefinedNumericVariable, /*IsLegacyLineExpr=*/false, SM);
+      LocalNumVar1Ref, DefinedNumericVariable, /*IsLegacyLineExpr=*/false,
+      /*LineNumber=*/2, &Cxt, SM);
+  EXPECT_TRUE(bool(ExpressionAST));
+  ExpressionVal = (*ExpressionAST)->eval();
+  EXPECT_TRUE(errorToBool(ExpressionVal.takeError()));
+  ExpressionAST = P.parseNumericSubstitutionBlock(
+      LocalNumVar2Ref, DefinedNumericVariable, /*IsLegacyLineExpr=*/false,
+      /*LineNumber=*/2, &Cxt, SM);
   EXPECT_TRUE(bool(ExpressionAST));
   ExpressionVal = (*ExpressionAST)->eval();
   EXPECT_TRUE(errorToBool(ExpressionVal.takeError()));
   EmptyVar = Cxt.getPatternVarValue(EmptyVarStr);
   EXPECT_TRUE(errorToBool(EmptyVar.takeError()));
   // Clear again because parseNumericSubstitutionBlock would have created a
   // dummy variable and stored it in GlobalNumericVariableTable.
   Cxt.clearLocalVars();
 
   // Redefine global variables and check variables are defined again.
   GlobalDefines.emplace_back(std::string("$GlobalVar=BAR"));
   GlobalDefines.emplace_back(std::string("#$GlobalNumVar=36"));
   EXPECT_FALSE(errorToBool(Cxt.defineCmdlineVariables(GlobalDefines, SM)));
   StringRef GlobalVarStr = "$GlobalVar";
   StringRef GlobalNumVarRef = bufferize(SM, "$GlobalNumVar");
   Expected<StringRef> GlobalVar = Cxt.getPatternVarValue(GlobalVarStr);
   EXPECT_TRUE(bool(GlobalVar));
   EXPECT_EQ(*GlobalVar, "BAR");
   P = FileCheckPattern(Check::CheckPlain, &Cxt, 3);
   ExpressionAST = P.parseNumericSubstitutionBlock(
-      GlobalNumVarRef, DefinedNumericVariable, /*IsLegacyLineExpr=*/false, SM);
+      GlobalNumVarRef, DefinedNumericVariable, /*IsLegacyLineExpr=*/false,
+      /*LineNumber=*/3, &Cxt, SM);
   EXPECT_TRUE(bool(ExpressionAST));
   ExpressionVal = (*ExpressionAST)->eval();
   EXPECT_TRUE(bool(ExpressionVal));
   EXPECT_EQ(*ExpressionVal, 36U);
 
   // Clear local variables and check global variables remain defined.
   Cxt.clearLocalVars();
   EXPECT_FALSE(errorToBool(Cxt.getPatternVarValue(GlobalVarStr).takeError()));
   P = FileCheckPattern(Check::CheckPlain, &Cxt, 4);
   ExpressionAST = P.parseNumericSubstitutionBlock(
-      GlobalNumVarRef, DefinedNumericVariable, /*IsLegacyLineExpr=*/false, SM);
+      GlobalNumVarRef, DefinedNumericVariable, /*IsLegacyLineExpr=*/false,
+      /*LineNumber=*/4, &Cxt, SM);
   EXPECT_TRUE(bool(ExpressionAST));
   ExpressionVal = (*ExpressionAST)->eval();
   EXPECT_TRUE(bool(ExpressionVal));
   EXPECT_EQ(*ExpressionVal, 36U);
 }
 } // namespace