diff --git a/lib/IRGen/GenDecl.cpp b/lib/IRGen/GenDecl.cpp
index cb35a96febc4c..60aabd107152e 100644
--- a/lib/IRGen/GenDecl.cpp
+++ b/lib/IRGen/GenDecl.cpp
@@ -1105,11 +1105,8 @@ void IRGenerator::emitGlobalTopLevel(llvm::StringSet<> *linkerDirectives) {
     IGM->emitSILDifferentiabilityWitness(&dw);
   }
 
-  // Emit code coverage mapping data for all modules
-  for (auto Iter : *this) {
-    IRGenModule *IGM = Iter.second;
-    IGM->emitCoverageMapping();
-  }
+  // Emit code coverage mapping data.
+  PrimaryIGM->emitCoverageMapping();
 
   for (auto Iter : *this) {
     IRGenModule *IGM = Iter.second;
diff --git a/test/Profiler/Inputs/coverage_num_threads1.swift b/test/Profiler/Inputs/coverage_num_threads1.swift
deleted file mode 100644
index 6ca641732e7e1..0000000000000
--- a/test/Profiler/Inputs/coverage_num_threads1.swift
+++ /dev/null
@@ -1 +0,0 @@
-func func1() {}
diff --git a/test/Profiler/Inputs/coverage_num_threads2.swift b/test/Profiler/Inputs/coverage_num_threads2.swift
deleted file mode 100644
index 639ea1b4ad4b7..0000000000000
--- a/test/Profiler/Inputs/coverage_num_threads2.swift
+++ /dev/null
@@ -1 +0,0 @@
-func func2() {}
diff --git a/test/Profiler/coverage_num_threads.swift b/test/Profiler/coverage_num_threads.swift
deleted file mode 100644
index 1a50c76335596..0000000000000
--- a/test/Profiler/coverage_num_threads.swift
+++ /dev/null
@@ -1,12 +0,0 @@
-// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -num-threads 0 -emit-ir %S/Inputs/coverage_num_threads1.swift | %FileCheck %s -check-prefix=SINGLE-SOURCE --implicit-check-not="llvm_coverage_mapping ="
-
-// SINGLE-SOURCE: llvm_coverage_mapping =
-
-// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -num-threads 0 -emit-ir %S/Inputs/coverage_num_threads1.swift %S/Inputs/coverage_num_threads2.swift | %FileCheck %s -check-prefix=SINGLE-OBJECT --implicit-check-not="llvm_coverage_mapping ="
-
-// SINGLE-OBJECT: llvm_coverage_mapping =
-
-// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -num-threads 2 -emit-ir %S/Inputs/coverage_num_threads1.swift %S/Inputs/coverage_num_threads2.swift | %FileCheck %s -check-prefix=MULTIPLE-OBJECTS --implicit-check-not="llvm_coverage_mapping ="
-
-// MULTIPLE-OBJECTS: llvm_coverage_mapping =
-// MULTIPLE-OBJECTS: llvm_coverage_mapping =