[Coverage] Fix an issue where improper coverage mapping data could be loaded for an inline function.

If an inline function is observed but unused in a translation unit, dummy
coverage mapping data with zero hash is stored for this function.
If such a coverage mapping section came earlier than real one, the latter
was ignored. As a result, llvm-cov was unable to show coverage information
for those functions.

Differential Revision: http://reviews.llvm.org/D20286

llvm-svn: 270194

4 files changed, 54 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.covmapping b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.covmapping
new file mode 100644
index 00000000000..4722129fc18
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.covmapping
diff --git a/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.cpp b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.cpp
new file mode 100644
index 00000000000..a0892b1e156
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.cpp
@@ -0,0 +1,5 @@
+#include "prefer_used_to_unused.h"
+
+int main() {
+  return sampleFunc(5) + simpleFunc(5);
+}
diff --git a/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.proftext b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.proftext
new file mode 100644
index 00000000000..dd3e704a090
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/prefer_used_to_unused.proftext
@@ -0,0 +1,25 @@
+_Z10sampleFunci
+# Func Hash:
+10
+# Num Counters:
+2
+# Counter Values:
+1
+1
+
+main
+# Func Hash:
+0
+# Num Counters:
+1
+# Counter Values:
+1
+
+_Z10simpleFunci
+# Func Hash:
+0
+# Num Counters:
+1
+# Counter Values:
+1
+
diff --git a/llvm/test/tools/llvm-cov/prefer_used_to_unused.h b/llvm/test/tools/llvm-cov/prefer_used_to_unused.h
new file mode 100644
index 00000000000..a053fdd72c7
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/prefer_used_to_unused.h
@@ -0,0 +1,24 @@
+// Check that llvm-cov loads real coverage mapping data for a function
+// even though dummy coverage data for that function comes first.
+// Dummy coverage data is exported if the definition of an inline function
+// is seen but the function is not used in the translation unit.
+
+// If you need to rebuild the 'covmapping' file for this test, please use
+// the following commands:
+// clang++ -fprofile-instr-generate -fcoverage-mapping -o tmp -x c++ prefer_used_to_unused.h prefer_used_to_unused.cpp
+// llvm-cov convert-for-testing -o prefer_used_to_unused.covmapping tmp
+
+// RUN: llvm-profdata merge %S/Inputs/prefer_used_to_unused.proftext -o %t.profdata
+// RUN: llvm-cov show %S/Inputs/prefer_used_to_unused.covmapping -instr-profile %t.profdata -filename-equivalence %s | FileCheck %s
+
+// Coverage data for this function has a non-zero hash value if it is used in the translation unit.
+inline int sampleFunc(int A) { // CHECK:      1| [[@LINE]]|inline int sampleFunc(int A) {
+  if (A > 0)                   // CHECK-NEXT: 1| [[@LINE]]|  if (A > 0)
+    return A;                  // CHECK-NEXT: 1| [[@LINE]]|    return A;
+  return 0;                    // CHECK-NEXT: 0| [[@LINE]]|  return 0;
+}                              // CHECK-NEXT: 1| [[@LINE]]|}
+
+// The hash for this function is zero in both cases, either it is used in the translation unit or not.
+inline int simpleFunc(int A) { // CHECK:      1| [[@LINE]]|inline int simpleFunc(int A) {
+  return A;                    // CHECK-NEXT: 1| [[@LINE]]|  return A;
+}                              // CHECK-NEXT: 1| [[@LINE]]|}