diff --git a/Makefile.config.in b/Makefile.config.in
index d34a2d51a933..2c4f1119e3f8 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -117,6 +117,11 @@ HOST_OS=@HOST_OS@
 # Target operating system for which LLVM will compile for.
 TARGET_OS=@TARGET_OS@
 
+ifeq ($(TARGET_OS),Bitrig)
+PROJ_docsdir  := $(PROJ_prefix)/share/docs/llvm
+PROJ_mandir   := $(PROJ_prefix)/man
+endif
+
 # Host hardware architecture
 HOST_ARCH=@HOST_ARCH@
 # Target hardware architecture
diff --git a/autoconf/config.sub b/autoconf/config.sub
index 673d62bfbf5b..612bff3de8f3 100755
--- a/autoconf/config.sub
+++ b/autoconf/config.sub
@@ -1354,7 +1354,7 @@ case $os in
 	      | -os2* | -vos* | -palmos* | -uclinux* | -nucleus* \
 	      | -morphos* | -superux* | -rtmk* | -rtmk-nova* | -windiss* \
 	      | -powermax* | -dnix* | -nx6 | -nx7 | -sei* | -dragonfly* \
-	      | -skyos* | -haiku* | -rdos* | -toppers* | -drops* | -es*)
+	      | -skyos* | -haiku* | -rdos* | -toppers* | -drops* | -es* | -bitrig*)
 	# Remember, each alternative MUST END IN *, to match a version number.
 		;;
 	-qnx*)
diff --git a/configure b/configure
index ba5ecbef334f..ec9ff0f34781 100755
--- a/configure
+++ b/configure
@@ -3966,6 +3966,11 @@ else
     llvm_cv_no_link_all_option="-Wl,--no-whole-archive"
     llvm_cv_os_type="DragonFly"
     llvm_cv_platform_type="Unix" ;;
+  *-*-bitrig*)
+    llvm_cv_link_all_option="-Wl,--whole-archive"
+    llvm_cv_no_link_all_option="-Wl,--no-whole-archive"
+    llvm_cv_os_type="DragonFly"
+    llvm_cv_platform_type="Unix" ;;
   *-*-hpux*)
     llvm_cv_link_all_option="-Wl,--whole-archive"
     llvm_cv_no_link_all_option="-Wl,--no-whole-archive"
@@ -4052,6 +4057,8 @@ else
     llvm_cv_target_os_type="NetBSD" ;;
   *-*-dragonfly*)
     llvm_cv_target_os_type="DragonFly" ;;
+  *-*-bitrig*)
+    llvm_cv_target_os_type="Bitrig" ;;
   *-*-hpux*)
     llvm_cv_target_os_type="HP-UX" ;;
   *-*-interix*)
@@ -9204,13 +9211,22 @@ fi
 
 if test "$LLVM_ENABLE_THREADS" -eq 1 && test "$ENABLE_PTHREADS" -eq 1 ; then
 
+if test "$llvm_cv_os_type" = "Bitrig" ; then
+{ echo "$as_me:$LINENO: checking for pthread_mutex_init in -pthread" >&5
+echo $ECHO_N "checking for pthread_mutex_init in -pthread... $ECHO_C" >&6; }
+else
 { echo "$as_me:$LINENO: checking for pthread_mutex_init in -lpthread" >&5
 echo $ECHO_N "checking for pthread_mutex_init in -lpthread... $ECHO_C" >&6; }
+fi
 if test "${ac_cv_lib_pthread_pthread_mutex_init+set}" = set; then
   echo $ECHO_N "(cached) $ECHO_C" >&6
 else
   ac_check_lib_save_LIBS=$LIBS
-LIBS="-lpthread  $LIBS"
+if test "$llvm_cv_os_type" = "Bitrig" ; then
+  LIBS="-pthread $LIBS"
+else
+  LIBS="-lpthread $LIBS"
+fi
 cat >conftest.$ac_ext <<_ACEOF
 /* confdefs.h.  */
 _ACEOF
@@ -9286,7 +9302,11 @@ if test $ac_cv_lib_pthread_pthread_mutex_init = yes; then
 #define HAVE_LIBPTHREAD 1
 _ACEOF
 
+if test "$llvm_cv_os_type" = "Bitrig" ; then
+  LIBS="-pthread $LIBS"
+else
   LIBS="-lpthread $LIBS"
+fi
 
 fi
 
diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index 754b5b924717..b0155cb2bcc6 100644
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -406,6 +406,7 @@ class X86Subtarget final : public X86GenSubtargetInfo {
   bool isTargetFreeBSD() const { return TargetTriple.isOSFreeBSD(); }
   bool isTargetDragonFly() const { return TargetTriple.isOSDragonFly(); }
   bool isTargetSolaris() const { return TargetTriple.isOSSolaris(); }
+  bool isTargetBitrig() const { return TargetTriple.isOSBitrig(); }
 
   bool isTargetELF() const { return TargetTriple.isOSBinFormatELF(); }
   bool isTargetCOFF() const { return TargetTriple.isOSBinFormatCOFF(); }
diff --git a/tools/llvm-config/CMakeLists.txt b/tools/llvm-config/CMakeLists.txt
index 50c84e6c3d08..f10d01bd13f4 100644
--- a/tools/llvm-config/CMakeLists.txt
+++ b/tools/llvm-config/CMakeLists.txt
@@ -5,9 +5,15 @@ set(BUILDVARIABLES_OBJPATH ${CMAKE_CURRENT_BINARY_DIR}/BuildVariables.inc)
 
 # Compute the substitution values for various items.
 get_property(LLVM_SYSTEM_LIBS_LIST TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS)
-foreach(l ${LLVM_SYSTEM_LIBS_LIST})
-  set(SYSTEM_LIBS ${SYSTEM_LIBS} "-l${l}")
-endforeach()
+if (${CMAKE_SYSTEM_NAME} MATCHES "Bitrig")
+  foreach(l ${LLVM_SYSTEM_LIBS_LIST})
+    set(SYSTEM_LIBS ${SYSTEM_LIBS} "-${l}")
+  endforeach()
+else()
+  foreach(l ${LLVM_SYSTEM_LIBS_LIST})
+    set(SYSTEM_LIBS ${SYSTEM_LIBS} "-l${l}")
+  endforeach()
+endif()
 string(REPLACE ";" " " SYSTEM_LIBS "${SYSTEM_LIBS}")
 
 # Use configure_file to create BuildVariables.inc.