[PATCH] [msan] -fsanitize-memory-track-origins=[level] flag and docs.

[Alexey Samsonov]

  LGTM modulo comments below.


================
Comment at: lib/Driver/SanitizerArgs.cpp:168
@@ +167,3 @@
+  if (NeedsMsan) {
+    Arg *A = Args.getLastArg(options::OPT_fsanitize_memory_track_origins_EQ,
+                             options::OPT_fsanitize_memory_track_origins,
----------------
if (Arg *A = ....) {

}

================
Comment at: test/Driver/fsanitize.c:96
@@ +95,3 @@
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=0 -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-0
+// CHECK-TRACK-ORIGINS-0-NOT: sanitize-memory-track-origins
+
----------------
Use the same check-prefix for this and the previous test case (group them together)

================
Comment at: test/Driver/fsanitize.c:99
@@ +98,3 @@
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=1 -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
+// CHECK-TRACK-ORIGINS-1: -fsanitize-memory-track-origins=1
+
----------------
Use the same check-prefix for this and the first test case (group them together)

================
Comment at: test/Driver/fsanitize.c:106
@@ -91,2 +105,3 @@
+// CHECK-TRACK-ORIGINS-3: error: invalid value '3' in '-fsanitize-memory-track-origins=3'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=vptr -fno-sanitize=vptr -fsanitize=undefined,address %s -### 2>&1
----------------
Add a test case(s) with overloaded value of -fsanitize-memory-track-origins. E.g.:

  -fsanitize-memory-track-origins=2 -fno-sanitize-memory-track-origins
results in
  -fsanitize-memory-track-origins=0
passed to frontend



http://llvm-reviews.chandlerc.com/D3118