From 0e93e26d3742e0660cf0e486b0961160da0f0e3a Mon Sep 17 00:00:00 2001
From: Justin Bogner <mail@justinbogner.com>
Date: Mon, 4 May 2015 04:09:38 +0000
Subject: [PATCH] llvm-cov: Warn if object file is newer than profile

Looking at coverage with an out of date profile can be confusing.
Provide a little hint that something might be wrong.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236408 91177308-0d34-0410-b5e6-96231b3b80d8
---
 tools/llvm-cov/CodeCoverage.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/llvm-cov/CodeCoverage.cpp b/tools/llvm-cov/CodeCoverage.cpp
index 0331a02dfcc..f85f3b13b67 100644
--- a/tools/llvm-cov/CodeCoverage.cpp
+++ b/tools/llvm-cov/CodeCoverage.cpp
@@ -195,7 +195,20 @@ CodeCoverageTool::createSourceFileView(StringRef SourceFile,
   return View;
 }
 
+static bool modifiedTimeGT(StringRef LHS, StringRef RHS) {
+  sys::fs::file_status Status;
+  if (sys::fs::status(LHS, Status))
+    return false;
+  auto LHSTime = Status.getLastModificationTime();
+  if (sys::fs::status(RHS, Status))
+    return false;
+  auto RHSTime = Status.getLastModificationTime();
+  return LHSTime > RHSTime;
+}
+
 std::unique_ptr<CoverageMapping> CodeCoverageTool::load() {
+  if (modifiedTimeGT(ObjectFilename, PGOFilename))
+    errs() << "warning: profile data may be out of date - object is newer\n";
   auto CoverageOrErr = CoverageMapping::load(ObjectFilename, PGOFilename,
                                              CoverageArch);
   if (std::error_code EC = CoverageOrErr.getError()) {