Index: lld/trunk/ELF/Driver.cpp
===================================================================
--- lld/trunk/ELF/Driver.cpp
+++ lld/trunk/ELF/Driver.cpp
@@ -860,10 +860,12 @@
   if (Config->OutputFile.empty())
     Config->OutputFile = "a.out";
 
-  // Fail early if the output file is not writable. If a user has a long link,
-  // e.g. due to a large LTO link, they do not wish to run it and find that it
-  // failed because there was a mistake in their command-line.
-  if (!isFileWritable(Config->OutputFile))
+  // Fail early if the output file or map file is not writable. If a user has a
+  // long link, e.g. due to a large LTO link, they do not wish to run it and
+  // find that it failed because there was a mistake in their command-line.
+  if (!isFileWritable(Config->OutputFile, "output file"))
+    return;
+  if (!isFileWritable(Config->MapFile, "map file"))
     return;
 
   // Use default entry point name if no name was given via the command
Index: lld/trunk/ELF/Filesystem.h
===================================================================
--- lld/trunk/ELF/Filesystem.h
+++ lld/trunk/ELF/Filesystem.h
@@ -15,7 +15,7 @@
 namespace lld {
 namespace elf {
 void unlinkAsync(StringRef Path);
-bool isFileWritable(StringRef Path);
+bool isFileWritable(StringRef Path, StringRef FileDescription);
 }
 }
 
Index: lld/trunk/ELF/Filesystem.cpp
===================================================================
--- lld/trunk/ELF/Filesystem.cpp
+++ lld/trunk/ELF/Filesystem.cpp
@@ -70,9 +70,9 @@
 // FileOutputBuffer doesn't touch a desitnation file until commit()
 // is called. We use that class without calling commit() to predict
 // if the given file is writable.
-bool elf::isFileWritable(StringRef Path) {
+bool elf::isFileWritable(StringRef Path, StringRef Desc) {
   if (auto EC = FileOutputBuffer::create(Path, 1).getError()) {
-    error("cannot open output file " + Path + ": " + EC.message());
+    error("cannot open " + Desc + " " + Path + ": " + EC.message());
     return false;
   }
   return true;
Index: lld/trunk/test/ELF/early-exit-for-bad-paths.s
===================================================================
--- lld/trunk/test/ELF/early-exit-for-bad-paths.s
+++ lld/trunk/test/ELF/early-exit-for-bad-paths.s
@@ -2,25 +2,32 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 
 # RUN: not ld.lld %t.o -o does_not_exist/output 2>&1 | \
-# RUN:   FileCheck %s -check-prefixes=NO-DIR,CHECK
+# RUN:   FileCheck %s -check-prefixes=NO-DIR-OUTPUT,CHECK
 # RUN: not ld.lld %t.o -o %s/dir_is_a_file 2>&1 | \
-# RUN:   FileCheck %s -check-prefixes=DIR-IS-FILE,CHECK
+# RUN:   FileCheck %s -check-prefixes=DIR-IS-OUTPUT,CHECK
 
 # RUN: echo "OUTPUT(\"does_not_exist/output\")" > %t.script
 # RUN: not ld.lld %t.o %t.script 2>&1 | \
-# RUN:   FileCheck %s -check-prefixes=NO-DIR,CHECK
+# RUN:   FileCheck %s -check-prefixes=NO-DIR-OUTPUT,CHECK
 # RUN: echo "OUTPUT(\"%s/dir_is_a_file\")" > %t.script
 # RUN: not ld.lld %t.o %t.script 2>&1 | \
-# RUN:   FileCheck %s -check-prefixes=DIR-IS-FILE,CHECK
+# RUN:   FileCheck %s -check-prefixes=DIR-IS-OUTPUT,CHECK
 
-# NO-DIR: error: cannot open output file does_not_exist/output:
-# DIR-IS-FILE: error: cannot open output file {{.*}}/dir_is_a_file:
+# RUN: not ld.lld %t.o -o %t -Map=does_not_exist/output 2>&1 | \
+# RUN:   FileCheck %s -check-prefixes=NO-DIR-MAP,CHECK
+# RUN: not ld.lld %t.o -o %t -Map=%s/dir_is_a_file 2>&1 | \
+# RUN:   FileCheck %s -check-prefixes=DIR-IS-MAP,CHECK
+
+# NO-DIR-OUTPUT: error: cannot open output file does_not_exist/output:
+# DIR-IS-OUTPUT: error: cannot open output file {{.*}}/dir_is_a_file:
+# NO-DIR-MAP: error: cannot open map file does_not_exist/output:
+# DIR-IS-MAP: error: cannot open map file {{.*}}/dir_is_a_file:
 
 # We should exit before doing the actual link. If an undefined symbol error is
 # discovered we haven't bailed out early as expected.
 # CHECK-NOT: undefined_symbol
 
-# RUN: not ld.lld %t.o -o / 2>&1 | FileCheck %s -check-prefixes=ROOT
+# RUN: not ld.lld %t.o -o / 2>&1 | FileCheck %s -check-prefixes=ROOT,CHECK
 # ROOT: error: cannot open output file /
 
   .globl _start
Index: lld/trunk/test/ELF/map-file.s
===================================================================
--- lld/trunk/test/ELF/map-file.s
+++ lld/trunk/test/ELF/map-file.s
@@ -59,4 +59,4 @@
 
 // RUN: not ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -Map=/ 2>&1 \
 // RUN:  | FileCheck -check-prefix=FAIL %s
-// FAIL: cannot open /
+// FAIL: cannot open map file /