[llvm-cov] Add error message for missing profdata on report and export subcommands.

[zequanwu]

Summary

When profdata is missing on report and export commands, the error message is
indistinguishable from missing instrumented binary file. This adds the error
message for report and export commands.

[zequanwu]

fix test.

[hans]

lgtm

llvm/test/tools/llvm-cov/misssing-profdata.test

-RUN: not llvm-cov show -instr-profile=%t.nonexistent %t.nonexistent 2>&1 | FileCheck %s
-CHECK: Could not read profile data
+RUN: not llvm-cov show -instr-profile=%t.nonexistent.profdata %t.nonexistent 2>&1 | FileCheck %s
+RUN: not llvm-cov export -instr-profile=%t.nonexistent.profdata %t.nonexistent 2>&1 | FileCheck %s
+RUN: not llvm-cov report -instr-profile=%t.nonexistent.profdata %t.nonexistent 2>&1 | FileCheck %s
+
+CHECK: nonexistent.profdata: Could not read profile data!

llvm/tools/llvm-cov/CodeCoverage.cpp

if (ViewOpts.hasOutputDirectory()) {
     if (auto E = sys::fs::create_directories(ViewOpts.ShowOutputDirectory)) {
       error("Could not create output directory!", E.message());
       return 1;
     }
   }
 
   sys::fs::file_status Status;
   if (std::error_code EC = sys::fs::status(PGOFilename, Status)) {
-    error("Could not read profile data!", EC.message());
+    error("Could not read profile data!" + EC.message(), PGOFilename);
     return 1;
   }
 
   auto ModifiedTime = Status.getLastModificationTime();
   std::string ModifiedTimeStr = to_string(ModifiedTime);
   size_t found = ModifiedTimeStr.rfind(':');
   ViewOpts.CreatedTimeStr = (found != std::string::npos)
                                 ? "Created: " + ModifiedTimeStr.substr(0, found)
int CodeCoverageTool::doReport(int argc, const char **argv,
   if (ViewOpts.Format == CoverageViewOptions::OutputFormat::HTML) {
     error("HTML output for summary reports is not yet supported.");
     return 1;
   } else if (ViewOpts.Format == CoverageViewOptions::OutputFormat::Lcov) {
     error("Lcov format should be used with 'llvm-cov export'.");
     return 1;
   }
 
+  sys::fs::file_status Status;
+  if (std::error_code EC = sys::fs::status(PGOFilename, Status)) {
+    error("Could not read profile data!" + EC.message(), PGOFilename);
+    return 1;
+  }
+
   auto Coverage = load();
   if (!Coverage)
     return 1;
 
   CoverageReport Report(ViewOpts, *Coverage.get());
   if (!ShowFunctionSummaries) {
     if (SourceFiles.empty())
       Report.renderFileReports(llvm::outs(), IgnoreFilenameFilters);
int CodeCoverageTool::doExport(int argc, const char **argv,
 
   if (ViewOpts.Format != CoverageViewOptions::OutputFormat::Text &&
       ViewOpts.Format != CoverageViewOptions::OutputFormat::Lcov) {
     error("Coverage data can only be exported as textual JSON or an "
           "lcov tracefile.");
     return 1;
   }
 
+  sys::fs::file_status Status;
+  if (std::error_code EC = sys::fs::status(PGOFilename, Status)) {
+    error("Could not read profile data!" + EC.message(), PGOFilename);
+    return 1;
+  }
+
   auto Coverage = load();
   if (!Coverage) {
     error("Could not load coverage information");
     return 1;
   }
 
   std::unique_ptr<CoverageExporter> Exporter;