diff --git a/test/ClangModules/autolinking.swift b/test/ClangModules/autolinking.swift
index 64cd70ef25e03..3ceec2cf31182 100644
--- a/test/ClangModules/autolinking.swift
+++ b/test/ClangModules/autolinking.swift
@@ -11,7 +11,11 @@
 // RUN: %target-swift-frontend %s -sdk %S/Inputs -I %S/Inputs/custom-modules -emit-ir -disable-autolink-framework LinkFramework -o %t/with-disabled.ll
 // RUN: FileCheck --check-prefix=CHECK-WITH-DISABLED %s < %t/with-disabled.ll
 
+// Linux uses a different autolinking mechanism, based on
+// swift-autolink-extract. This file tests the Darwin mechanism.
 // UNSUPPORTED: OS=linux-gnu
+// UNSUPPORTED: OS=linux-gnueabihf
+// UNSUPPORTED: OS=freebsd
 
 import LinkMusket
 import LinkFramework
diff --git a/test/Frontend/embed-bitcode.swift b/test/Frontend/embed-bitcode.swift
index f9e33533ab709..bdd3c2f546f4d 100644
--- a/test/Frontend/embed-bitcode.swift
+++ b/test/Frontend/embed-bitcode.swift
@@ -4,7 +4,11 @@
 // RUN: llvm-objdump -macho -section="__LLVM,__bitcode" %t.o | FileCheck -check-prefix=MARKER %s
 // RUN: llvm-objdump -macho -section="__LLVM,__swift_cmdline" %t.o | FileCheck -check-prefix=MARKER-CMD %s
 
+// This file tests Mach-O file output, but Linux variants do not produce Mach-O
+// files.
 // UNSUPPORTED: OS=linux-gnu
+// UNSUPPORTED: OS=linux-gnueabihf
+// UNSUPPORTED: OS=freebsd
 
 // MARKER: Contents of (__LLVM,__bitcode) section
 // MARKER-NEXT: 00
diff --git a/test/Interpreter/repl_autolinking.swift b/test/Interpreter/repl_autolinking.swift
index bc072d83b25ab..5fc27b3fa4394 100644
--- a/test/Interpreter/repl_autolinking.swift
+++ b/test/Interpreter/repl_autolinking.swift
@@ -8,6 +8,8 @@
 
 // REQUIRES: swift_repl
 // UNSUPPORTED: OS=linux-gnu
+// UNSUPPORTED: OS=linux-gnueabihf
+// UNSUPPORTED: OS=freebsd
 
 // This test checks that autolinking works in the REPL.
 
diff --git a/test/Serialization/autolinking.swift b/test/Serialization/autolinking.swift
index 09e3e262e4938..cb412dc28f082 100644
--- a/test/Serialization/autolinking.swift
+++ b/test/Serialization/autolinking.swift
@@ -20,7 +20,11 @@
 // RUN: %target-swift-frontend -emit-ir -parse-stdlib -module-name someModule -module-link-name module %S/../Inputs/empty.swift -autolink-force-load | FileCheck --check-prefix=FORCE-LOAD %s
 // RUN: %target-swift-frontend -emit-ir -parse-stdlib -module-name someModule -module-link-name 0module %S/../Inputs/empty.swift -autolink-force-load | FileCheck --check-prefix=FORCE-LOAD-HEX %s
 
+// Linux uses a different autolinking mechanism, based on
+// swift-autolink-extract. This file tests the Darwin mechanism.
 // UNSUPPORTED: OS=linux-gnu
+// UNSUPPORTED: OS=linux-gnueabihf
+// UNSUPPORTED: OS=freebsd
 
 import someModule