InstrProf: Avoid creating profile names for symbols in system headers

We don't emit any coverage mapping for uncovered functions that come
from system headers, but we were creating a GlobalVariable with each
of their names. This is wasteful since the linker will need to dead
strip the unused symbols, and it can lead to issues when merging
coverage with others TUs that do have coverage for those functions.

llvm-svn: 226764

1 files changed, 21 insertions, 0 deletions

diff --git a/clang/test/CoverageMapping/unused_names.c b/clang/test/CoverageMapping/unused_names.c
new file mode 100644
index 00000000000..b1317209610
--- /dev/null
+++ b/clang/test/CoverageMapping/unused_names.c
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fprofile-instr-generate -fcoverage-mapping -emit-llvm -o - %s | FileCheck %s
+
+// Since foo is never emitted, there should not be a profile name for it.
+
+// CHECK-NOT: @__llvm_profile_name_foo =
+// CHECK: @__llvm_profile_name_bar =
+// CHECK-NOT: @__llvm_profile_name_foo =
+
+#ifdef IS_SYSHEADER
+
+#pragma clang system_header
+inline int foo() { return 0; }
+
+#else
+
+#define IS_SYSHEADER
+#include __FILE__
+
+int bar() { return 0; }
+
+#endif