[llvm-cov gcov] Fix calculating coverage statistics of template functions

[ikudrin]

Summary

Template functions share the same lines in source files, so the common container of lines' properties cannot be used to calculate the coverage statistics of individual functions.

> cat tmpl.cpp
template <int N> int test() { return N; }
int main() { return test<1>() + test<2>(); }
> clang++ --coverage tmpl.cpp -o tmpl
> ./tmpl
> llvm-cov gcov tmpl.cpp -f
...
Function '_Z4testILi1EEiv'
Lines executed:100.00% of 1

Function '_Z4testILi2EEiv'
Lines executed:-nan% of 0
...
> llvm-cov-patched gcov tmpl.cpp -f
...
Function '_Z4testILi1EEiv'
Lines executed:100.00% of 1

Function '_Z4testILi2EEiv'
Lines executed:100.00% of 1
...

[jhenderson]

I don't know a nything about how this works unfortunately, so can't review it really.

FYI, there's a pre-merge test failure and clang-format issue.

[MaskRay]

curl -L 'https://reviews.llvm.org/D121390?download=1' does not include the contents for tmpl.gcno and tmpl.gcda.

So I just run:

clang++ --coverage tmpl.cpp -o tmpl
./tmpl
llvm-cov gcov tmpl.cpp -t

I do not see a difference with and w/o the patch.

Template functions share the same lines in source files, so the common container of lines' properties cannot be used to calculate the coverage of individual functions.

Suppose there is indeed a difference. It's useful to attach a C++ program and line execution counts before and after this patch, for the relevant lines.

llvm/test/tools/llvm-cov/gcov/tmpl.cpp

1 ↗

(On Diff #414399)

llvm-cov gcov %s --gcno=%p/Inputs/tmpl.gcno --gcda=%p/Inputs/tmpl.gcda

14 ↗

(On Diff #414399)

It's useful to dump llvm-cov gcov -t and test the line counts for the three lines, to better leverage this test file.

[ikudrin]

• Fixed a formatting issue
• Updated the test

In D121390#3374554, @jhenderson wrote:

FYI, there's a pre-merge test failure

That is probably because tmpl.gcda and tmpl.gcno are binaries and I do not know how to upload them to the review. I have tried git diff --binary for this patch, but with little success.

and clang-format issue.

Thanks! Fixed.

In D121390#3374685, @MaskRay wrote:

curl -L 'https://reviews.llvm.org/D121390?download=1' does not include the contents for tmpl.gcno and tmpl.gcda.

So I just run:

clang++ --coverage tmpl.cpp -o tmpl
./tmpl
llvm-cov gcov tmpl.cpp -t

I do not see a difference with and w/o the patch.

The patch fixes -f, not -t.

Template functions share the same lines in source files, so the common container of lines' properties cannot be used to calculate the coverage of individual functions.

Suppose there is indeed a difference. It's useful to attach a C++ program and line execution counts before and after this patch, for the relevant lines.

Added an example into the description.

llvm/test/tools/llvm-cov/gcov/tmpl.cpp

14 ↗

(On Diff #414399)

I'm not sure I follow you. The patch fixes and the test checks the coverage statistics for template functions (-f), not execution counts (-t).

[MaskRay]

> llvm-cov gcov tmpl.cpp -f
...
Function '_Z4testILi2EEiv'
Lines executed:-nan% of 0

Perhaps include

Function '_Z4testILi1EEiv'
Lines executed:100.00% of 1

in the message as well.

llvm/lib/ProfileData/GCOV.cpp

666

Optional: llvm:: is usually omitted for llvm/lib files.

llvm/test/tools/llvm-cov/gcov/tmpl.cpp

14 ↗

(On Diff #414399)

I suggest using llvm-cov gcov -t -f to better leverage the test. I know this patch fixes an issue. But with little efforts (adding line execution counts for -t) this patch can add more coverage that we currently lack (there are very little C++ template tests): test<1>() + test<2>(); on the same line may be interesting for the line execution counts.

[ikudrin]

• Removed llvm::
• Update the test

llvm/test/tools/llvm-cov/gcov/tmpl.cpp

14 ↗

(On Diff #414399)

-t suppresses -f, and a passed source file name is ignored if --gcno=/--gcda= are specified, so I have to rework the test

llvm/lib/ProfileData/GCOV.cpp

 //===- GCOV.cpp - LLVM coverage tool --------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // GCOV implements the interface to read and write coverage files that use
 // 'gcov' format.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ProfileData/GCOV.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Demangle/Demangle.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
std::string Context::getCoveragePath(StringRef filename,
   return CoveragePath;
 }
 
 void Context::collectFunction(GCOVFunction &f, Summary &summary) {
   SourceInfo &si = sources[f.srcIdx];
   if (f.startLine >= si.startLineToFunctions.size())
     si.startLineToFunctions.resize(f.startLine + 1);
   si.startLineToFunctions[f.startLine].push_back(&f);
+  SmallSet<uint32_t, 16> lines;
+  SmallSet<uint32_t, 16> linesExec;
   for (const GCOVBlock &b : f.blocksRange()) {
     if (b.lines.empty())
       continue;
     uint32_t maxLineNum = *std::max_element(b.lines.begin(), b.lines.end());
     if (maxLineNum >= si.lines.size())
       si.lines.resize(maxLineNum + 1);
     for (uint32_t lineNum : b.lines) {
       LineInfo &line = si.lines[lineNum];
-      if (!line.exists)
+      if (lines.insert(lineNum).second)
         ++summary.lines;
-      if (line.count == 0 && b.count)
+      if (b.count && linesExec.insert(lineNum).second)
         ++summary.linesExec;
       line.exists = true;
       line.count += b.count;
       line.blocks.push_back(&b);
     }
   }
 }
 

llvm/test/tools/llvm-cov/gcov/Inputs/tmpl.cpp

+template <int N>
+int test() { return N; }
+
+int main() { return test<1>() + test<2>(); }

llvm/test/tools/llvm-cov/gcov/tmpl.test

+# Check that the coverage statistics for template functions are calculated as expected.
+
+RUN: rm -rf %t
+RUN: mkdir %t
+RUN: cd %t
+RUN: cp %p/Inputs/tmpl* .
+
+RUN: llvm-cov gcov tmpl.cpp -f | FileCheck %s --check-prefix=F
+RUN: llvm-cov gcov tmpl.cpp -t | FileCheck %s --check-prefix=T
+
+F:      Function '_Z4testILi1EEiv'
+F-NEXT: Lines executed:100.00% of 1
+F:      Function '_Z4testILi2EEiv'
+F-NEXT: Lines executed:100.00% of 1
+
+T:      -: 1:template <int N>
+T-NEXT: 2: 2:int test() { return N; }
+T-NEXT: -: 3:
+T-NEXT: 1: 4:int main() { return test<1>() + test<2>(); }