Index: clang/lib/Driver/ToolChains/AVR.cpp
===================================================================
--- clang/lib/Driver/ToolChains/AVR.cpp
+++ clang/lib/Driver/ToolChains/AVR.cpp
@@ -375,8 +375,7 @@
 
   // Only add default libraries if the user hasn't explicitly opted out.
   if (!Args.hasArg(options::OPT_nostdlib) &&
-      !Args.hasArg(options::OPT_nodefaultlibs) &&
-      GCCInstallation.isValid()) {
+      !Args.hasArg(options::OPT_nodefaultlibs) && GCCInstallation.isValid()) {
     GCCInstallPath = GCCInstallation.getInstallPath();
     std::string GCCParentPath(GCCInstallation.getParentLibPath());
     getProgramPaths().push_back(GCCParentPath + "/../bin");
@@ -429,9 +428,13 @@
   // Compute information about the target AVR.
   std::string CPU = getCPUName(D, Args, getToolChain().getTriple());
   llvm::Optional<StringRef> FamilyName = GetMCUFamilyName(CPU);
+  llvm::Optional<std::string> AVRLibcRoot = TC.findAVRLibcInstallation();
   llvm::Optional<unsigned> SectionAddressData = GetMCUSectionAddressData(CPU);
 
-  std::string Linker = getToolChain().GetProgramPath(getShortName());
+  // Compute the linker program path, and use GNU "avr-ld" as default.
+  bool IsLLD = false;
+  std::string Linker = getToolChain().GetLinkerPath(&IsLLD);
+
   ArgStringList CmdArgs;
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
 
@@ -450,17 +453,11 @@
   if (!Args.hasArg(options::OPT_nostdlib) &&
       !Args.hasArg(options::OPT_nodefaultlibs)) {
     if (!CPU.empty()) {
-        Optional<StringRef> FamilyName = GetMCUFamilyName(CPU);
-        Optional<std::string> AVRLibcRoot = TC.findAVRLibcInstallation();
-
       if (!FamilyName) {
         // We do not have an entry for this CPU in the family
         // mapping table yet.
         D.Diag(diag::warn_drv_avr_family_linking_stdlibs_not_implemented)
             << CPU;
-      } else if (TC.getGCCInstallPath().empty()) {
-        // We can not link since there is no avr-ld.
-        D.Diag(diag::warn_drv_avr_gcc_not_found);
       } else if (!AVRLibcRoot) {
         // No avr-libc found and so no runtime linked.
         D.Diag(diag::warn_drv_avr_libc_not_found);
@@ -473,7 +470,6 @@
         LinkStdlib = true;
       }
     }
-
     if (!LinkStdlib)
       D.Diag(diag::warn_drv_avr_stdlib_not_linked);
   }
@@ -508,11 +504,37 @@
 
     CmdArgs.push_back("--end-group");
 
-    // 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
-    // than the bare minimum supports.
-    CmdArgs.push_back(Args.MakeArgString(std::string("-m") + *FamilyName));
+    // Add user specified linker script.
+    const Arg *LDS = Args.getLastArg(options::OPT_T);
+    if (LDS) {
+      CmdArgs.push_back(Args.MakeArgString("-T"));
+      CmdArgs.push_back(Args.MakeArgString(LDS->getValue()));
+    }
+
+    // Add specific options for different linkers.
+    if (IsLLD && !LDS) {
+      // We must explicitly specify `__vectors` as the entry, if the user
+      // does not specify the '-T' option.
+      CmdArgs.push_back(Args.MakeArgString("-e"));
+      CmdArgs.push_back(Args.MakeArgString("__vectors"));
+      // Add the default linker script for current AVR device, if user does not
+      // specify the '-T' option. The default linker script should has already
+      // integrated into avr-libc, and whose full path is expected to be
+      // $AVR-LIBC/lib/ldscripts/$FamilyName.x .
+      if (AVRLibcRoot && FamilyName) {
+        std::string Prefix(*AVRLibcRoot + "/lib/ldscripts/");
+        if (llvm::sys::fs::is_directory(Prefix)) {
+          CmdArgs.push_back(Args.MakeArgString("-T"));
+          CmdArgs.push_back(Args.MakeArgString(Prefix + *FamilyName + ".x"));
+        }
+      }
+    } else if (Linker.find("avr-ld") != std::string::npos) {
+      // 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
+      // than the bare minimum supports.
+      CmdArgs.push_back(Args.MakeArgString(std::string("-m") + *FamilyName));
+    }
   }
 
   C.addCommand(std::make_unique<Command>(
Index: clang/test/Driver/avr-toolchain.c
===================================================================
--- clang/test/Driver/avr-toolchain.c
+++ clang/test/Driver/avr-toolchain.c
@@ -53,8 +53,24 @@
 // LINKA-NOT: warning: {{.*}} data section address
 
 // RUN: %clang -### --target=avr --sysroot=%S/Inputs/ -mmcu=atmega328 %s 2>&1 | FileCheck --check-prefixes=NOGCC %s
-// NOGCC: warning: no avr-gcc installation can be found on the system, cannot link standard libraries
+// NOGCC: error: invalid linker
 // NOGCC: warning: standard library not linked and so no interrupt vector table or compiler runtime routines will be linked
 // NOGCC-NOT: warning: {{.*}} microcontroller
 // NOGCC-NOT: warning: {{.*}} avr-libc
 // NOGCC-NOT: warning: {{.*}} data section address
+
+// RUN: %clang -### --target=avr --sysroot=%S/Inputs/basic_avr_tree -mmcu=atmega328 %s -fuse-ld=avrld 2>&1 | FileCheck --check-prefix=NOLD %s
+// NOLD: error: invalid linker
+
+// RUN: %clang -### --target=avr --sysroot=%S/Inputs/basic_avr_tree -mmcu=atmega328 %s -fuse-ld=lld 2>&1 | FileCheck --check-prefix=LLD %s
+// LLD: {{".*lld"}} {{.*}} "-e" "__vectors" "-T" {{".*avr5.x"}}
+// LLD-NOT: "avr-ld"
+// 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"
+
+// RUN: %clang -### --target=avr --sysroot=%S/Inputs/basic_avr_tree -mmcu=atmega328 %s -fuse-ld=lld -T avr.lds 2>&1 | FileCheck --check-prefix=LDS1 %s
+// LDS1: "-T" "avr.lds"
+// LDS1-NOT: "-e"
+// LDS1-NOT: "-mavr5"