extern "C" {

#include "InstrProfiling.h"

COMPILER_RT_VISIBILITY int __llvm_profile_runtime;
}

namespace {

class RegisterRuntime {
public:
  RegisterRuntime() {
    __llvm_profile_register_write_file_atexit();
    __llvm_profile_initialize_file();
  }
};

RegisterRuntime Registration;

}

1 file changed, 2 insertions(+)
lib/Driver/ToolChains.cpp | 2 ++

modified   lib/Driver/ToolChains.cpp
@@ -1366,6 +1366,8 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
                               getTriple().getArchName() +
                               ".a");
     Arguments.push_back(context.Args.MakeArgString(LibProfile));
+    Arguments.push_back(context.Args.MakeArgString("-Xlinker"));
+    Arguments.push_back(context.Args.MakeArgString("-u__llvm_profile_runtime"));
   }

   // Always add the stdlib

$ swiftenv global   local-dev
$ swiftc -o hello -profile-generate -profile-coverage-mapping hello.swift
$ ./hello
$ ls
default.profraw  hello  hello.swift
$ llvm-profdata merge -o hello.profdata default.profraw
$  llvm-cov show ./hello -instr-profile=hello.profdat\
a hello.swift
    999|    1|func test80(count: Int)-> Int{
    999|    2|    var sum = 0;
  80.9k|    3|    for i in 0...80 {
  80.9k|    4|        sum += i
    999|    5|    }
    999|    6|    return sum
    999|    7|}
    999|    8|func test20(count: Int)-> Int {
    999|    9|    var sum = 0;
  20.9k|   10|    for i in 0...20 {
  20.9k|   11|        sum += i
    999|   12|    }
    999|   13|//    print("\(sum) ")
    999|   14|    return sum
    999|   15|}
       |   16|var count20 = 20
       |   17|var count80 = 80
      1|   18|func mainmain() {
      1|   19|    var sum = 0
    999|   20|    for _ in 1..<1000 {
    999|   21|        sum += test80(count: count80)
    999|   22|        sum += test20(count: count20)
      1|   23|    }
      1|   24|//    print(sum)
      1|   25|}
       |   26|
       |   27|
       |   28|mainmain()