diff --git a/clang/lib/Driver/ToolChains/AVR.cpp b/clang/lib/Driver/ToolChains/AVR.cpp
--- a/clang/lib/Driver/ToolChains/AVR.cpp
+++ b/clang/lib/Driver/ToolChains/AVR.cpp
@@ -545,6 +545,9 @@
     // Add user specified linker script.
     Args.AddAllArgs(CmdArgs, options::OPT_T);
 
+    if (Args.hasFlag(options::OPT_mrelax, options::OPT_mno_relax, true))
+      CmdArgs.push_back("--relax");
+
     // Specify the family name as the emulation mode to use.
     // This is almost always required because otherwise avr-ld
     // will assume 'avr2' and warn about the program being larger
diff --git a/clang/test/Driver/avr-ld.c b/clang/test/Driver/avr-ld.c
--- a/clang/test/Driver/avr-ld.c
+++ b/clang/test/Driver/avr-ld.c
@@ -1,44 +1,45 @@
 // RUN: %clang -### --target=avr -mmcu=at90s2313 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKA %s
-// LINKA: {{".*ld.*"}} {{.*}} {{"-L.*tiny-stack"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lat90s2313" {{.*}} "--end-group" "-mavr2"
+// LINKA: {{".*ld.*"}} {{.*}} {{"-L.*tiny-stack"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lat90s2313" {{.*}} "--end-group" "--relax" "-mavr2"
 
-// RUN: %clang -### --target=avr -mmcu=at90s8515 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKB %s
-// LINKB: {{".*ld.*"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lat90s8515" {{.*}} "--end-group" "-mavr2"
+// RUN: %clang -### --target=avr -mmcu=at90s8515 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s -mrelax 2>&1 | FileCheck -check-prefix LINKB %s
+// LINKB: {{".*ld.*"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lat90s8515" {{.*}} "--end-group" "--relax" "-mavr2"
 
-// RUN: %clang -### --target=avr -mmcu=attiny13 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKC %s
+// RUN: %clang -### --target=avr -mmcu=attiny13 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s -mno-relax 2>&1 | FileCheck -check-prefix LINKC %s
 // LINKC: {{".*ld.*"}} {{.*}} {{"-L.*avr25/tiny-stack"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lattiny13" {{.*}} "--end-group" "-mavr25"
+// LINLC-NOT: "--relax"
 
 // RUN: %clang -### --target=avr -mmcu=attiny44 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKD %s
-// LINKD: {{".*ld.*"}} {{.*}} {{"-L.*avr25"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lattiny44" {{.*}} "--end-group" "-mavr25"
+// LINKD: {{".*ld.*"}} {{.*}} {{"-L.*avr25"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-lattiny44" {{.*}} "--end-group" "--relax" "-mavr25"
 
 // RUN: %clang -### --target=avr -mmcu=atmega103 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKE %s
-// LINKE: {{".*ld.*"}} {{.*}} {{"-L.*avr31"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-latmega103" {{.*}} "--end-group" "-mavr31"
+// LINKE: {{".*ld.*"}} {{.*}} {{"-L.*avr31"}} {{.*}} "-Tdata=0x800060" "--start-group" {{.*}} "-latmega103" {{.*}} "--end-group" "--relax" "-mavr31"
 
 // RUN: %clang -### --target=avr -mmcu=atmega8u2 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKF %s
-// LINKF: {{".*ld.*"}} {{.*}} {{"-L.*avr35"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega8u2" {{.*}} "--end-group" "-mavr35"
+// LINKF: {{".*ld.*"}} {{.*}} {{"-L.*avr35"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega8u2" {{.*}} "--end-group" "--relax" "-mavr35"
 
 // RUN: %clang -### --target=avr -mmcu=atmega48pa --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKG %s
-// LINKG: {{".*ld.*"}} {{.*}} {{"-L.*avr4"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega48pa" {{.*}} "--end-group" "-mavr4"
+// LINKG: {{".*ld.*"}} {{.*}} {{"-L.*avr4"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega48pa" {{.*}} "--end-group" "--relax" "-mavr4"
 
 // RUN: %clang -### --target=avr -mmcu=atmega328 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKH %s
-// LINKH: {{".*ld.*"}} {{.*}} {{"-L.*avr5"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega328" {{.*}} "--end-group" "-mavr5"
+// LINKH: {{".*ld.*"}} {{.*}} {{"-L.*avr5"}} {{.*}} "-Tdata=0x800100" "--start-group" {{.*}} "-latmega328" {{.*}} "--end-group" "--relax" "-mavr5"
 
 // RUN: %clang -### --target=avr -mmcu=atmega1281 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKI %s
-// LINKI: {{".*ld.*"}} {{.*}} {{"-L.*avr51"}} {{.*}} "-Tdata=0x800200" "--start-group" {{.*}} "-latmega1281" {{.*}} "--end-group" "-mavr51"
+// LINKI: {{".*ld.*"}} {{.*}} {{"-L.*avr51"}} {{.*}} "-Tdata=0x800200" "--start-group" {{.*}} "-latmega1281" {{.*}} "--end-group" "--relax" "-mavr51"
 
 // RUN: %clang -### --target=avr -mmcu=atmega2560 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKJ %s
-// LINKJ: {{".*ld.*"}} {{.*}} {{"-L.*avr6"}} {{.*}} "-Tdata=0x800200" "--start-group" {{.*}} "-latmega2560" {{.*}} "--end-group" "-mavr6"
+// LINKJ: {{".*ld.*"}} {{.*}} {{"-L.*avr6"}} {{.*}} "-Tdata=0x800200" "--start-group" {{.*}} "-latmega2560" {{.*}} "--end-group" "--relax" "-mavr6"
 
 // RUN: %clang -### --target=avr -mmcu=attiny10 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKK %s
-// LINKK: {{".*ld.*"}} {{.*}} {{"-L.*avrtiny"}} {{.*}} "-Tdata=0x800040" "--start-group" {{.*}} "-lattiny10" {{.*}} "--end-group" "-mavrtiny"
+// LINKK: {{".*ld.*"}} {{.*}} {{"-L.*avrtiny"}} {{.*}} "-Tdata=0x800040" "--start-group" {{.*}} "-lattiny10" {{.*}} "--end-group" "--relax" "-mavrtiny"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega16a4 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKL %s
-// LINKL: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega2"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega16a4" {{.*}} "--end-group" "-mavrxmega2"
+// LINKL: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega2"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega16a4" {{.*}} "--end-group" "--relax" "-mavrxmega2"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega64b3 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKM %s
-// LINKM: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega4"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega64b3" {{.*}} "--end-group" "-mavrxmega4"
+// LINKM: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega4"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega64b3" {{.*}} "--end-group" "--relax" "-mavrxmega4"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega128a3u --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKN %s
-// LINKN: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega6"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega128a3u" {{.*}} "--end-group" "-mavrxmega6"
+// LINKN: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega6"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega128a3u" {{.*}} "--end-group" "--relax" "-mavrxmega6"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega128a1 --rtlib=libgcc --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINKO %s
-// LINKO: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega7"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega128a1" {{.*}} "--end-group" "-mavrxmega7"
+// LINKO: {{".*ld.*"}} {{.*}} {{"-L.*avrxmega7"}} {{.*}} "-Tdata=0x802000" "--start-group" {{.*}} "-latxmega128a1" {{.*}} "--end-group" "--relax" "-mavrxmega7"
diff --git a/clang/test/Driver/avr-toolchain.c b/clang/test/Driver/avr-toolchain.c
--- a/clang/test/Driver/avr-toolchain.c
+++ b/clang/test/Driver/avr-toolchain.c
@@ -67,7 +67,7 @@
 // LLD-NOT: "-mavr5"
 
 // RUN: %clang -### --target=avr --sysroot=%S/Inputs/basic_avr_tree -mmcu=atmega328 %s -T avr.lds 2>&1 | FileCheck --check-prefix=LDS0 %s
-// LDS0: "-T" "avr.lds" "-mavr5"
+// LDS0: "-T" "avr.lds" "--relax" "-mavr5"
 
 // RUN: %clang -### --target=avr --sysroot=%S/Inputs/basic_avr_tree -mmcu=atmega328 %s -fuse-ld=%S/Inputs/basic_avr_tree/usr/bin/ld.lld -T avr.lds 2>&1 | FileCheck --check-prefix=LDS1 %s
 // LDS1: "-T" "avr.lds"