X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FCommandGuide%2FFileCheck.rst;h=809eee0469d01a369efe35d412260cb0e7112ed3;hb=0a230e0d985625a3909cb78fd867a3abaf434565;hp=256970b36240634eafb3b6eadfadaa4b6d6cf300;hpb=ed04fd2053a7a696f8e2aa850e87cef1353c34e3;p=oota-llvm.git

diff --git a/docs/CommandGuide/FileCheck.rst b/docs/CommandGuide/FileCheck.rst
index 256970b3624..809eee0469d 100644
--- a/docs/CommandGuide/FileCheck.rst
+++ b/docs/CommandGuide/FileCheck.rst
@@ -43,7 +43,8 @@ OPTIONS
 
  By default, FileCheck canonicalizes input horizontal whitespace (spaces and
  tabs) which causes it to ignore these differences (a space will match a tab).
- The :option:`--strict-whitespace` argument disables this behavior.
+ The :option:`--strict-whitespace` argument disables this behavior. End-of-line
+ sequences are canonicalized to UNIX-style ``\n`` in all modes.
 
 .. option:: -version
 
@@ -193,6 +194,55 @@ can be used:
    ; CHECK: ret i8
    }
 
+The "CHECK-DAG:" directive
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If it's necessary to match strings that don't occur in a strictly sequential
+order, "``CHECK-DAG:``" could be used to verify them between two matches (or
+before the first match, or after the last match). For example, clang emits
+vtable globals in reverse order. Using ``CHECK-DAG:``, we can keep the checks
+in the natural order:
+
+.. code-block:: c++
+
+    // RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s
+
+    struct Foo { virtual void method(); };
+    Foo f;  // emit vtable
+    // CHECK-DAG: @_ZTV3Foo =
+
+    struct Bar { virtual void method(); };
+    Bar b;
+    // CHECK-DAG: @_ZTV3Bar =
+
+
+With captured variables, ``CHECK-DAG:`` is able to match valid topological
+orderings of a DAG with edges from the definition of a variable to its use.
+It's useful, e.g., when your test cases need to match different output
+sequences from the instruction scheduler. For example,
+
+.. code-block:: llvm
+
+   ; CHECK-DAG: add [[REG1:r[0-9]+]], r1, r2
+   ; CHECK-DAG: add [[REG2:r[0-9]+]], r3, r4
+   ; CHECK:     mul r5, [[REG1]], [[REG2]]
+
+In this case, any order of that two ``add`` instructions will be allowed.
+
+``CHECK-NOT:`` directives could be mixed with ``CHECK-DAG:`` directives to
+exclude strings between the surrounding ``CHECK-DAG:`` directives. As a result,
+the surrounding ``CHECK-DAG:`` directives cannot be reordered, i.e. all
+occurrences matching ``CHECK-DAG:`` before ``CHECK-NOT:`` must not fall behind
+occurrences matching ``CHECK-DAG:`` after ``CHECK-NOT:``. For example,
+
+.. code-block:: llvm
+
+   ; CHECK-DAG: BEFORE
+   ; CHECK-NOT: NOT
+   ; CHECK-DAG: AFTER
+
+This case will reject input strings where ``BEFORE`` occurs after ``AFTER``.
+
 FileCheck Pattern Matching Syntax
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~