[llvm-cov] Avoid over-counting covered lines and regions

* Fix an unsigned integer overflow in the logic that computes the
  number of uncovered lines in a function.

* When aggregating region and line coverage summaries, take into account
  that different instantiations may have a different number of regions.

The new test case provides test coverage for both bugs. I also verified
this change by preparing a coverage report for a stage2 build of llc --
the new assertions should detect any outstanding over-counting bugs.

Fixes PR34613.

llvm-svn: 313417

1 files changed, 29 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-cov/Inputs/multiple_objects/header.h b/llvm/test/tools/llvm-cov/Inputs/multiple_objects/header.h
new file mode 100644
index 00000000000..03b37cd2dbb
--- /dev/null
+++ b/llvm/test/tools/llvm-cov/Inputs/multiple_objects/header.h
@@ -0,0 +1,29 @@
+static inline void f1() {
+#ifdef DEF
+  if (false && false)
+    return;
+
+  if (true || false || true)
+    return;
+
+  if (true && false)
+    return;
+#endif
+}
+
+template<typename T>
+void f2(T **x) {
+#ifdef DEF
+  if (false && false)
+    *x = nullptr;
+
+  if (true || false || true)
+    *x = nullptr;
+
+  if (true && false)
+    *x = nullptr;
+#endif
+}
+
+static inline void f3() {
+}